U.S. patent application number 10/900793 was filed with the patent office on 2005-02-24 for multi-channel network monitoring apparatus, signal replicating device, and systems including such apparatus and devices, and enclosure for multi-processor equipment.
This patent application is currently assigned to Agilent Technologies, Inc.. Invention is credited to Carson, Douglas John, Lunn, George Crowther, MacIsaac, William Ross, Reynolds, Alastair.
Application Number | 20050041684 10/900793 |
Document ID | / |
Family ID | 34796852 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050041684 |
Kind Code |
A1 |
Reynolds, Alastair ; et
al. |
February 24, 2005 |
Multi-channel network monitoring apparatus, signal replicating
device, and systems including such apparatus and devices, and
enclosure for multi-processor equipment
Abstract
A multi-channel network monitoring apparatus has input
connectors for network signals to be monitored and four channel
processors in a rack-mountable chassis/enclosure for receiving and
processing a respective pair of incoming signals to produce
monitoring results. Each processor operates independently of the
others and is replaceable without interrupting their operation. LAN
connectors enable onward communication of the monitoring results. A
cross-point switch routes each incoming signal to a selected
processor and can re-route a channel to another processor in the
event of processor outage. Each processor has a self-contained
sub-system of processing modules interconnected via a
CPU-peripheral interface in a backplane, which provides a separate
peripheral interface for each processor. The backplane provides
locations for processors to lie horizontally across a major portion
of the backplane area facing the front of the enclosure, and a
location for an interface module over a minor portion of that area
facing the rear, so as to provide external connectors at the rear
of the enclosure. A power supply module is positioned over another
portion of the backplane area, on the same side as the interface
module. The location of the power supply module behind the
backplane saves height and/or width in the rack.
Inventors: |
Reynolds, Alastair;
(Linlithgow, GB) ; Carson, Douglas John;
(Englewood, CO) ; Lunn, George Crowther; (West
Lothian, GB) ; MacIsaac, William Ross; (Dunfermline,
GB) |
Correspondence
Address: |
Richard P. Berg
c/o LADAS & PARRY
Suite 2100
Los Angeles
CA
90036-5679
US
|
Assignee: |
Agilent Technologies, Inc.
|
Family ID: |
34796852 |
Appl. No.: |
10/900793 |
Filed: |
July 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10900793 |
Jul 27, 2004 |
|
|
|
09672593 |
Sep 28, 2000 |
|
|
|
Current U.S.
Class: |
370/463 |
Current CPC
Class: |
H04L 43/00 20130101;
H04L 49/555 20130101 |
Class at
Publication: |
370/463 |
International
Class: |
H04L 012/66 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 1999 |
GB |
9923142.5 |
Oct 1, 1999 |
GB |
9923143.3 |
Claims
1-12. (canceled)
13. An enclosure as claimed in claim 25, together with a processing
sub-system comprising one processing module having specialised
capability for processing a specific type of input signal to be
analysed, and another processing module of general purpose type for
receiving partially processed data from the first processing module
and for further processing and reducing said data for onward
communication.
14-24. (canceled)
25. A computer equipment chassis comprising a housing and a
backplane providing locations for a plurality of independent
processing sub-systems, each processing sub-system comprising first
and second processing modules to be separately mounted on the
backplane at adjacent locations, the backplane providing at least
four independent host-peripheral interfaces, each extending only
between the adjacent locations for said first and second processing
modules, and each being configured such that in operation the first
processing module operates as a peripheral and the second
processing module operates as host.
26. A chassis as claimed in claim 25, wherein the housing and
backplane further provide a location for a multi-channel interface
module providing external connections for all of the processing
sub-systems, the backplane routing signals from the interface
module to the appropriate sub-systems.
27. A chassis as claimed in claim 26, wherein said housing and
backplane further provide a location for a switching module, such
that each external connection can be routed and re-routed to
different processing sub-systems.
28. A chassis as claimed in claimed 25, wherein the backplane
further provides interconnections to the locations for the
processing sub-systems for communication externally of the
housing.
29. A chassis as claimed in claim 28, wherein said housing and
backplane further provide a management module location for routing
of said communication from the locations for the processing
sub-systems to external connectors.
30-50. (canceled)
51. A chassis as claimed in claim 25, wherein the host-peripheral
interfaces are cPCI interfaces.
52. A chassis as claimed in claim 25, wherein there are at least
four independent processing sub-systems and host-peripheral
interfaces.
Description
INTRODUCTION
[0001] The invention relates to telecommunications networks, and in
particular to apparatus and systems for monitoring traffic in
broadband networks.
[0002] In telecommunication networks, network element connectivity
can be achieved using optical fibre bearers to carry data and voice
traffic.
[0003] Data traffic on public telecommunication networks is
expected to exceed voice traffic with Internet Protocol (IP)
emerging as one data networking standard, in conjunction with
Asynchronous Transfer Mode (ATM) systems. Voice over IP is also
becoming an important application for many Internet service
providers with IP switches connecting IP networks to the public
telephony network (PSTN). IP can be carried over a Sonet transport
layer, either with or without ATM. In order to inter-operate with
the PSTN, IP switches are also capable of inter-working with SS7,
the common signalling system for telecommunications networks, as
defined by the International Telecommunications Union (ITU)
standard for the exchange of signalling messages over a common
signalling network.
[0004] Different protocols are used to set up calls according to
network type and supported services. The signalling traffic carries
messages to set up calls between the necessary network nodes. In
response to the SS7 messages, an appropriate link through the
transport network is established, to carry the actual data and
voice traffic (the payload data) for the duration of each call,.
Traditional SS7 links are time division multiplexed, so that the
same physical bearer may be carrying the signalling and the payload
data. The SS7 network is effectively an example of an "out of band"
signalling network, because the signalling is readily separated
from the payload. For ATM and IP networks, however, the signalling
and payload data is statistically multiplexed on the same bearer.
In the case of statistical multiplexing the receiver has to examine
each message/cell to decide if it is carrying signalling or payload
data. One protocol similar to SS7 used in such IP networks is known
as Gateway Control Protocol (GCP).
[0005] The monitoring of networks and their traffic is a
fundamental requirement of any system. The "health" of the network
must be monitored, to predict, detect and even anticipate failures,
overloads and so forth. Monitoring is also crucial to billing of
usage charges, both to end users and between service providers. The
reliability (percentage availability) of monitoring equipment is a
prime concern for service providers and users, and many
applications such as billing require "high availability" monitoring
systems, such that outages, due to breakdown or maintenance, must
be made extremely rare.
[0006] A widely-used monitoring system for SS7 signalling networks
is acceSS7 .TM. from Agilent Technologies (and previously from
Hewlett-Packard). An instrument extracts all the SS7 packetised
signals at Signalling Transfer Points (STPs), which are packet
switches analogous to IP routers, that route messages between end
points in SS7 networks. The need can be seen for similar monitoring
systems able to cope with combined IP/PSTN networks, especially at
gateways where the two protocols meet. A problem arises, however,
in the quantity of data that needs to be processed for the
monitoring of IP traffic. In Internet Protocol networks, there is
no out of band signalling network separate from the data traffic
itself. Rather, routing information is embedded in the packet
headers of the data transport network itself, and the full data
stream has to be processed by the monitoring equipment to extract
the necessary information as to network health, billing etc.
Moreover, IP communication is not based on allocating each "call"
with a link of fixed bandwidth for the duration of the call: rather
bandwidth is allocated by packets on demand, in a link shared with
any number of other data streams.
[0007] Accordingly, there is a need for a new kind of monitoring
equipment capable of grabbing the vast volume of data flowing in
the IP network bearers, and of processing it fast enough to extract
and analyse the routing and other information crucial to the
monitoring function. The requirements of extreme reliability
mentioned above apply equally in the new environment.
[0008] Networks such as these may be monitored using instruments
(generally referred to as probes) by making a passive optical
connection to the optical fibre bearer using an optical splitter.
However, this approach cannot be considered without due attention
to the optical power budget of the bearer, as the optical splitters
are lossy devices. In addition to this, it may be desirable to
monitor the same bearer many times or to monitor the same bearer
twice as part of a backup strategy for redundancy purposes. With
available instrumentation, this implies a multiplication of the
losses, and also disruption to the bearers as each new splitter is
installed. Issues of upgrading the transmitter and/or receiver
arise as losses mount up.
[0009] The inventors have analysed acceSS7 network monitoring
systems (unpublished at the present filing date). This shows that
the reasons for lack of availability of the system can be broken
down into three broad categories: unplanned outages, such as
software defects; planned outages, such as software and hardware
upgrades; and hardware failures. Further analysis shows that the
majority of operational hours lost are caused by planned and
unplanned maintenance, while hardware failures have a relatively
minor effect. increasing the redundancy of disk drives, power
supplies and the like, although psychologically comforting, can do
relatively little to improve system availability. The greatest
scope for reducing operational hours lost and hence increasing
availability is in the category of planned outages.
[0010] In order to implement a reliable monitoring system it would
therefore be advantageous to have an architecture with redundancy
allowing for spare probe units that is tolerant of both probe
failure and probe reconfiguration, and provides software
redundancy.
[0011] Monitoring equipment designed for this purpose does not
currently exist. Service providers may therefore use stand-alone
protocol analysers which are tools really intended for the network
commissioning stage. These usually terminate the fibre bearer, in
place of the product being installed, or they plug into a specific
test port on the product under test. Specific test software is then
needed for each product. Manufacturers have alternatively built
diagnostic capability into the network equipment itself, but each
perceives the problems differently, leading to a lack of
uniformity, and actual monitoring problems, as opposed to perceived
problems, may not be addressed.
[0012] Further considerations include the physical environment
needed to house such processing architecture. Such a hardware
platform should be as flexible as possible to allow for changes in
telecommunications technology and utilise standard building blocks
to ensure cross platform compatibility. For example, there exist
standards in the USA, as set out by the American National Standards
Institute (ANSI) and Bellcore, which differ from those of Europe as
set by the European Telecommunications Standards Institute (ETSI).
Versions of SS7 may also vary from country to country, owing to the
flexibility of the standard, although the ITU standard is generally
used at international gateways. The USA Bellcore Network
Equipment-Building System (NEBS) is of particular relevance to
rack-mounted telecommunications equipment as it provides design
standards for engineering construction and should be taken into
account when designing network monitoring equipment. Such standards
impose limitations such as connectivity and physical dimensions
upon equipment and, consequently, on cooling requirements and aisle
spacing of network rack equipment.
[0013] It is known that standard processing modules conforming for
example to the cPCI standard are suitable for use in
telecommunication applications. The further standard H.110 provides
a bus for multiplexing baseband telephony signals in the same
backplane as the cPCI bus. Even with Intel Pentium.TM. or similar
processors, however, such arrangements do not currently accommodate
the computing power needed for the capture and analysis of
broadband packet data. Examples of protocols and their data rates
to be accommodated in the monitored bearers in the future equipment
are for example DS3 (44 Mbit.s.sup.-1), OC3 (155 Mbit.s.sup.-1),
OC12 (622 Mbit.s.sup.-1) and OC48 (2.4 Gbit.s.sup.-1). Aside from
the volume of data to be handled, conventional chassis for housing
such modules do not also support probe architectures of the type
currently desired, both in terms of processing capability and also
to the extent that their dimensions do not suit the layout of
telecommunication equipment rooms such as may be designed to NEBS
allowing them to co-reside with network equipment.
[0014] For example, the typical general purpose chassis provides a
rack-mounted enclosure in which a backplane supports and
interconnects a number of cPCI cards, including a processor card
and peripheral cards, to form a functional system. The cards are
generally oriented vertically, with power supply (PSU) modules
located above or below. Fans force air through the enclosure from
bottom to top for cooling the modules. A peripheral card may have
input and output (I/O) connections on its front panel.
Alternatively, I/O connections may be arranged at the rear of the
enclosure, using a special "transition card". Examples of rack
widths in common use are 19 inch (483 mm) and 23 inch (584 mm). The
siting of racks in telecommunications equipment rooms implies an
enclosure depth should be little over 12 inches (305 mm). However,
cPCI and VME standard processor cards and compatible peripheral
cards are already 205 mm deep (including mountings) and the
conventional interface card mounted behind the back plane adds
another 130 mm. Moreover, although parts of the connector pin-outs
for cPCI products are standardised, different vendors use other
connectors differently for management bus signals and for LAN
connections. These variations must also be adapted to by dedicated
interconnect, and designs will often assume that cards from a
single vendor only are used.
[0015] In a first aspect the invention provides a rack-mountable
enclosure comprising a housing and interconnection backplane for
the mounting and interconnection of a plurality of card-shaped
processing modules and at least one interface module, the interface
module being arranged to provide a plurality of external connectors
and to transport signals via the backplane between each external
connection and an individual processing module, wherein:
[0016] said backplane provides locations for said processing
modules to lie across a major portion of the backplane area facing
a front side of the enclosure;
[0017] said backplane provides a location for said interface module
over a minor portion of the backplane area facing a rear side of
the enclosure, so as to provide said external connectors at the
rear of the enclosure; and
[0018] a power supply module for powering the modules within the
enclosure is positioned over another portion of the backplane area,
on the same side as the interface module.
[0019] This arrangement allows a compact housing to contain several
processing modules and to receive a corresponding number of
external connections, in a more compact and functionally dense
manner than known instrument chassis designs. In particular, the
location of the power supply module behind the backplane saves
height and/or width in the rack.
[0020] It will be understood that "front" and "rear" are used for
convenience, and their meanings can be reversed. One particular
benefit of the specified arrangement is that all external
connectors (and hence the associated cabling) can be located on one
side of the enclosure, allowing consistent access for all cables at
the rear in the crowded equipment rooms common to telecommunication
and other installations. Using cPCI standard processor and
peripheral cards, the depth of the enclosure can be kept within or
close to 12 inches (305 mm), no greater than the surrounding
telecommunication equipment.
[0021] The enclosure may be constructed so that the processor
modules lie generally horizontally when the enclosure is rack
mounted. Air paths may be defined through the enclosure so as to
pass from end to end thereof, along and between the processor
modules and, if necessary, the power supply and interface modules.
Fans may be included, optionally in a redundant configuration, to
ensure adequate air flow to cool the various components of the
enclosure.
[0022] The external connectors may provide inputs, outputs or both.
In a telecommunications network probe application, the transport of
data in the backplane will generally be inward, from the external
connectors to the processing modules. In particular, external input
connectors may be provided by the interface module for broadband
telecommunications signals, with high bandwidth interconnections
provided in the backplane. In principle, the backplane could
include optical interconnects. With present technology, however,
any necessary optical to electrical conversion will more likely be
included in the interface module. In other applications, for
example process control or computer telephony, the transport may be
in both directions, or outwards only. The transport via the
backplane may be in essentially the same format in which it
arrives. Alternatively, the interface module may change the format,
for example to multiplex several of the external signals onto a
single pair of conductors in the backplane. The enclosure and
modules will find particular application wherever a large quantity
of data needs to be processed at speed, and reduced by filtering
and aggregation to provide information for use elsewhere.
[0023] For flexibility and particularly for redundancy in fault and
maintenance situations, the enclosure may provide a location for at
least one switching module, whereby routing of signals between the
external connectors and individual processing modules can be
varied. The switching module may in particular comprise a
cross-point switch, in accordance with another aspect of the
invention, set forth in more detail elsewhere. It is assumed in
that case that the processing modules are "hot-swappable", so that
operation of other modules is unaffected by module replacement. The
switching module may be operable to route signals between one
external connector and a plurality of processing modules. This
allows increased processing capacity to be provided for each
external connector, whether this is used for redundancy or merely
to add processing functionality.
[0024] For additional redundancy in larger systems, the switching
module and interface module may provide for re-routing one of said
signals from an external input connector to an additional output
connector, to allow processing in another enclosure. The number of
external input connectors may exceed the capacity of processing
modules that can be accommodated, or may match it.
[0025] The backplane may separately provide local bus
interconnections for communication between the processing modules.
Said local bus interconnections may include a processor-peripheral
parallel bus, for example cPCI. The processing module locations may
be subdivided into groups, each group receiving a set of separately
pluggable modules which together co-operate for processing of a
given external signal. The backplane may in particular provide a
plurality of independent local buses, each for communication
between the modules of one group. The groups may each include a
first processor module having specific capability for a type of
input signal (such as IP packet data) to be analysed, and a second
processor module of generic type for receiving partially processed
data from the first processor module, and for further processing
and reducing said data for onward communication.
[0026] The first and second processing modules can be regarded as
packet and probe processor modules respectively, each such pair
forming a self-contained probe unit. It will be understood that
each probe processor card may be served by more than one packet
processor card, and references to pairs should not be construed as
excluding the presence of a further packet processor module in any
group.
[0027] In the specific embodiments disclosed herein, two separate
interface modules are provided at the rear side of the backplane. A
first interface module, being the one referred to above, is for the
signals to be processed (which broadly could mean input signals to
be analysed or output signals being generated). A second interface
module is provided for communication for control and management
purposes, such as the onward communication of the processing
results via LAN. These modules could of course be combined in one
physical module, or further sub-divided, according to design
requirements.
[0028] The external outputs may be connections to a computer Local
Area Network (LAN), which can also provide for remote control and
configuration of the processing modules. For redundancy of
operation, the LAN connections in the backplane can be unique to
each module, and can further be duplicated for each module.
Alternatively, all modules can communicate via a common LAN. The
backplane may provide a dedicated location for a management module
for selective routing of the LAN or other output communications
from the external connectors to the processing modules.
[0029] The backplane may further provide a communication bus
connecting all modules, for management functions including for
example power and cooling management. Said interconnections may for
example include an I.sup.2C or SMB bus carrying standard protocols.
For improved redundancy, separate buses may be provided for each
sub-system.
[0030] Combining the above features, according to a particular
embodiment of the invention in its first aspect, the backplane may
provide:
[0031] a plurality of pairs of processing module locations, each
pair comprising adjacent first and second processing module
locations;
[0032] a plurality of independent communication buses each
extending between the first processing module location and second
processing module location of a respective one of said pairs;
[0033] a plurality of independent interconnections each for
bringing a different external input signal from said interface
module to a respective one of said first processing module
location;
[0034] one or a plurality of independent interconnections for
bringing communication signals from said second processing module
locations to a second interface module.
[0035] The enclosure and backplane may further provide a location
for a communication and management module to provide one or more of
the following functions:
[0036] routing of processing module communication and management
signals;
[0037] communication (e.g. LAN) switching to route communications
from the processing modules to the outside world with sufficient
redundancy and bandwidth;
[0038] "magic packet" handling, to allow remote resetting of the
modules within the enclosure; and
[0039] environmental control, controlling fan speed in response to
operating temperatures sensed on each module.
[0040] Alternatively, the first aspect of the invention provides a
rack-mountable enclosure comprising a housing, a power supply
module, a fan assembly and an interconnection backplane for the
mounting and interconnection of a plurality of card-shaped
processing modules, wherein the processing modules in use are
arranged to lie generally horizontally in front of the backplane
and generally parallel with one another, the power supply module is
located behind the backplane, and the fan assembly is located to
left or right of the processing modules (in use, as viewed from the
front) so as to provide a generally horizontal airflow between
them.
[0041] A shared interface module or modules for providing external
connections to the backplane and hence to all of the processing
modules may also be located behind the backplane.
[0042] It is noted at this point that the cPCI standard defines a
number of physical connectors to be present on the backplane, but
only two of these (J1, J2) are specified as to their pin functions.
Although the second processing modules mentioned above are generic
processor cards based for example on Pentium (.TM. of Intel Corp.)
microprocessors, different card vendors use the remaining
connectors differently for communication and management signals
such as SMB and LAN connections.
[0043] According to a second aspect of the invention a
multi-processor equipment enclosure provides a housing and a
backplane providing locations for a plurality of processing
modules, and further providing a plurality of locations for a
configuration module corresponding to respective processing module
locations, each configuration module adapting the routing of
communication and management signals via the backplane, in
accordance with the vendor-specific implementation of the
processing module.
[0044] The configuration module locations may be on the backplane,
or on another card connected to the backplane. In the preferred
embodiment, a communication and management module is provided at a
specific location, and the configuration module locations are
provided on the management module.
[0045] In an alternative solution according to the second aspect of
the invention, a multi-processor equipment enclosure provides a
housing and a backplane providing interconnect for a plurality of
processing modules and a management module, the backplane
interconnect including generic portions standardised over a range
of processing modules and other portions specific to different
processing modules within said range, wherein said management
module is arranged to sense automatically the specific type of
processing module using protocols implemented by the modules via
connections in the generic portion of the interconnect, and to
route communication and management signals via the backplane, in
accordance with the specific implementation of each processing
module.
[0046] The type sensing protocols may for example be implemented
via geographic address lines in the standardised portion of a
compact PCI backplane.
[0047] It is noted that known chassis designs and backplanes do not
provide for several channels of signals to be monitored by
independent processing sub-systems within the same chassis,
especially when each monitoring unit processor in fact requires
more than one card slot for its implementation. In particular, for
monitoring of broadband communication signals in IP or similar
protocols, it is presently necessary to provide a first processing
module dedicated to a first stage of data acquisition and
processing, where the sheer quantity of broadband data would defeat
a general-purpose processor card, and a second processing module of
generic type, for further processing onward reporting of the data
processed by the first processing module.
[0048] According to a third aspect of the invention a computer
equipment chassis provides a housing and backplane providing
locations for at least four independent processing sub-systems,
each processing sub-system comprising first and second processing
modules separately mounted on the backplane at adjacent locations,
wherein the backplane provides at least four independent
CPU-peripheral interfaces, each extending only between the adjacent
locations of said first and second processing modules, the first
processing module operating as a peripheral and the second
processing module operating as host.
[0049] The enclosure and backplane may further provide a location
for a multi-channel interface module providing external connections
for all of the processing sub-systems, the backplane routing
signals from the interface module to the appropriate processing
sub-systems. The enclosure and backplane may further provide a
location for a switching module, such that each external connection
can be routed and re-routed to different processing
sub-systems.
[0050] The backplane may further provide interconnections between
the channel processors for communication externally of the
enclosure. The enclosure and backplane may further provide a
management module location for routing of said communication from
the channel processors to external connectors. Said
interconnections may form part of a computer local area network
(LAN). The enclosure and backplane may in fact provide multiple
redundant network connections in order that said onward
communication can continue in the event of a network outage.
[0051] The inventors have recognised that, particularly because
passive optical splitters have extremely high reliability, a probe
architecture which provides for replication and redundancy in the
monitoring system after the splitter would allow all the desired
functionality and reliability to be achieved, without multiple
physical taps in the network bearer, and hence without excessive
power loss and degradation in the system being monitored.
[0052] In a fourth aspect the invention provides a multi-channel
network monitoring apparatus for the monitoring of traffic in a
broadband telecommunications network, the apparatus comprising:
[0053] a plurality of external input connectors for receipt of
network signals to be monitored;
[0054] a plurality of channel processors mounted within a chassis,
each for receiving and processing a respective incoming signal to
produce monitoring results for onward communication, the incoming
network signals individually or in groups forming channels for the
purposes of the monitoring apparatus, each channel processor being
arranged to operate independently of the others and being
replaceable without interrupting their operation;
[0055] one or more external communication connectors for onward
communication of said monitoring results from the channel
processors; and
[0056] a switching unit;
[0057] wherein the external input connectors are connected to the
channel processors via said switching unit, the switching unit in
use routing each incoming signal to a selected channel processor
and being operable to re-route an incoming channel to another
selected channel processor in the event of processor outage.
[0058] The switching unit may further be operable to connect the
same incoming channel simultaneously to more than one channel
processor. The same bearer can therefore be monitored in different
ways, without the need for another physical tap.
[0059] The channel processors may be in the form of modules mounted
and interconnected on a common backplane. The switching unit may
comprise a further module mounted on said backplane. The external
input connectors may be provided by a common interface module
separate from or integrated with the switching unit.
[0060] The external communication connectors may be connected to
the channel processors via a communication management module and
via the backplane. The external communication connectors and
communication management module may optionally provide for said
onward communication to be implemented over plural independent
networks for redundancy. Redundancy of the networks may extend to
each channel processor itself providing two or more network
connections. In the particular embodiments described, the backplane
provides an independent connection between each respective channel
processor and the communication management module. This provides
better redundancy than shared network communication.
[0061] The channel processors may each comprise a self-contained
sub-system of host and peripheral processing modules interconnected
via a CPU-peripheral interface in the backplane, the backplane
providing a separate peripheral interface for each channel
processor. The interconnection may in particular comprise a
parallel peripheral interface such as cPCI.
[0062] The backplane and card-like modules may be provided in a
single rack-mountchassis, which may also house a power supply and
cooling fans. These may be arranged internally in accordance with
the first aspect of the invention, as set forth.
[0063] The switching unit may be operable to route any incoming
signal to any of the channel processors. The switching unit may
further provide for routing any of the incoming channels to an
further external connector, for processing by a channel processor
separate from the chassis.
[0064] The invention yet further provides a network monitoring
system wherein a first group of multi-channel network monitoring
apparatuses according to the fourth aspect of the invention as set
forth above are connected to receive a plurality of incoming
signals, wherein the switching unit of each apparatus in the first
group provides for routing any of its incoming channels to a
further external connector, the system further comprising at least
one further multi-channel network monitoring apparatus according to
the fourth aspect of the invention as set forth above, connected to
receive incoming channels from said further external connectors of
the first group of apparatuses, the further apparatus thereby
providing back-up in the event of a channel processor failure or
replacement within the first group of apparatuses.
[0065] The invention yet further provides a network monitoring
system wherein a plurality of multi-channel network monitoring
apparatuses according to the fourth aspect of the invention as set
forth above are connected to a larger plurality of incoming
channels via multiplexing means, the total number of channel
processors within the monitoring apparatuses being greater than the
number of incoming channels at any given time, such that any
incoming channel can be routed by the multiplexing means and
appropriate switching unit to an idle channel processor of one of
the monitoring apparatuses. This allows the system to continue
monitoring all channels in the event of failure or replacement of
any channel processor.
[0066] The number of channel processors may be greater than the
number of incoming channels by at least the number of channel
processors in each monitoring apparatus. This allows the system to
continue monitoring all channels in the event of failure or
replacement of one complete apparatus.
[0067] The multiplexing means may be formed by optical switches,
while the switching units within each monitoring apparatus operate
on signals after conversion to electrical form. Alternatively, the
multiplexing means may include electronic switches, while inputs
and outputs are converted to-and-from optical form for ease of
interconnection between separate enclosures. In principle, the
conversion from optical to electrical for could happen at any
point, from the network tap point to the processing module
itself.
[0068] The above systems will typically further comprise one or
more multi-channel optical power splitters, for tapping into active
optical communications bearers to obtain the said incoming signals
for the monitoring apparatuses. The redundancy and adaptability
within the monitoring system reduces the need for multiple
monitoring taps, preserving the integrity of the network.
[0069] In a fifth aspect the invention provides a multi-channel
replicating device for broadband optical signals, the device
comprising one or more modules having:
[0070] a first plurality of input connectors for receiving
broadband optical signals;
[0071] a larger plurality of output connectors for broadband
optical signals;
[0072] means for replicating each received broadband optical signal
to a plurality of said output connectors without digital
processing.
[0073] Such a device allows multiple monitoring applications to be
performed on a network signal with only one optical tap being
inserted in the physical bearer or the operating network.
Redundancy in the monitoring equipment can be provided, also with
the single bearer tap. Change in the configuration of the
monitoring equipment can be implemented without disturbing the
bearer operation, or even the other monitoring applications.
[0074] The replicating means may in particular involve components
for optical to electrical conversion and back to optical again.
[0075] The replicating device may further comprise an one or more
additional optical outputs, and a selector devices for selecting
which of the input signals is replicated at said additional output.
This selection can be useful in particular in response to fault
situations and planned outages within the network monitoring
equipment.
[0076] The invention in the fifth aspect further provides a
telecommunications network monitoring system comprising:
[0077] an optical splitting device, providing a tap signal for
monitoring signals carried by a bearer in a broadband
telecommunications network;
[0078] a plurality of network monitoring units, each for receiving
and analysing signals from a broadband optical bearer; and
[0079] a signal replicating device according to the fifth aspect of
the invention as set forth above, the signal replicating device
being connected so as to receive said optical tap signal, and to
provide replicas of said optical tap signal to inputs of two or
more of said network monitoring units.
BRIEF DESCRIPTION OF THE DRAWINGS
[0080] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying drawings, in
which:
[0081] FIG. 1 shows a model of a typical ATM network.
[0082] FIG. 2 shows a data collection and packet processing
apparatus connected to a physical telecommunications network via a
LAN/WAN interconnect.
[0083] FIG. 3 shows the basic functional architecture of a novel
network probe apparatus, as featured in FIG. 2.
[0084] FIG. 4 shows a simple network monitoring system which can be
implemented using the apparatus of the type shown in FIG. 3.
[0085] FIG. 5 shows another application of the apparatus of FIG. 4
giving 3+1 redundancy.
[0086] FIG. 6 shows a larger redundant network monitoring system
including a backup apparatus.
[0087] FIG. 7 shows an example of a modified probe apparatus
permitting a "daisy chain" configuration to provide extra
redundancy and/or processing power.
[0088] FIG. 8 shows an example of daisy chaining the probe chassis
of FIG. 7 giving 8+1 redundancy.
[0089] FIG. 9 shows a further application of the probe apparatus
giving added processing power per bearer.
[0090] FIG. 10 shows a second means of increasing processing power
by linking more than one chassis together.
[0091] FIG. 11 shows a signal replicating device (referred to as a
Broadband Bridging Isolator (BBI)) for use in a network monitoring
system.
[0092] FIG. 12 shows a typical configuration of a network
monitoring system using the BBI of FIG. 11 and several probe
apparatuses.
[0093] FIGS. 13A and 1 3B illustrate a process of upgrading the
processing power of a network monitoring system without
interrupting operation.
[0094] FIG. 14 is a functional schematic diagram of a generalised
network probe apparatus showing the functional relationships
between the major modules of the apparatus.
[0095] FIG. 15A shows the general physical layout of modules in a
specific network probe apparatus implemented in a novel chassis and
backplane.
[0096] FIG. 15B is a front view of the chassis and backplane of
FIG. 15A with all modules removed, showing the general layout of
connectors and interconnections in the backplane.
[0097] FIG. 15C is a rear view of the chassis and backplane of FIG.
15A with all modules removed, showing the general layout of
connectors and interconnections in the backplane, and showing in
cut-away form the location of a power supply module.
[0098] FIG. 16 shows in block schematic form the interconnections
between modules in the apparatus of FIGS. 15A-C.
[0099] FIG. 17 is a block diagram showing in more detail a
cross-point switch module in the apparatus of FIG. 16, and its
interconnections with other modules.
[0100] FIG. 18 is a block diagram showing in more detail a packet
processor module in the apparatus of FIG. 16, and its
interconnections with other modules.
[0101] FIG. 19 is a block diagram showing in more detail a combined
LAN and chassis management card in the apparatus of FIG. 16.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Background
[0102] FIG. 1 shows a model of a telecommunication network 10 based
on asynchronous transfer mode (ATM) bearers. Possible monitoring
points on various bearers in the network are shown at 20 and
elsewhere. Each bearer is generally an optical fibre carrying
packetised data with both routing information and data "payload"
travelling in the same data stream. Here "bearer" is used to mean
the physical media that carries the data and is distinct from a
"link", which in this context is defined to mean a logical stream
of data. Many links of data may be multiplexed onto a single
bearer. These definitions are provided for consistency in the
present description, however, and should not be taken to imply any
limitation of the applicability of the techniques disclosed, or on
the scope of the invention defined in the appended claims. Those
skilled in the art will sometimes use the term "channel" to refer
to a link (as defined), or "channel" may be used to refer to one of
a number of virtual channels being carried over one link, which
comprises the logical connection between two subscribers, or
between a subscriber and a service provider. Note that such
"channels" within the larger telecommunications network should not
be confused with the monitoring channels within the network probe
apparatus of the embodiments to be described hereinafter.
[0103] The payload may comprise voice traffic and/or other data.
Different protocols may be catered for, with examples showing
connections to Free Relay Gateway, ATM and DSLAM equipment being
illustrated. User-Network traffic 22 and Network-Network traffic 24
are shown here as dashed lines and solid lines respectively.
[0104] In FIG. 2 various elements 25-60 of a data collection and
packet processing system distributed at different sites are
provided for monitoring bearers L1-L8 etc. of a telecommunications
network. The bearers in the examples herein operate in pairs L1, L2
etc. for bi-directional traffic, but this is not universal, nor is
it essential to the invention. Each pair is conveniently monitored
by a separate probe unit 25, by means of optical splitters S1, S2
etc. inserted in the physical bearers. For example, one probe unit
25, which monitors bearers L1 and L2, is connected to a local area
network (LAN) 60, along with other units at the same site. The
probe unit 25 on an ATM/IP network must examine a vast quantity of
data, and can be programmed to filter the data by a Virtual Channel
(VC) as a means of reducing the onboard processing load. Filtering
by IP address can be used to the same effect in the case of IP over
SDH and other such optical networks. Similar techniques can be used
for other protocols. Site processors 40 collate and aggregate the
large quantity of information gathered by the probe units, and pass
the results via a Wide Area Network (WAN) 30 to a central site 65.
Here this information may be used for network planning and
operations. It may alternatively be used for billing according to
the volume of monitored traffic per subscriber or service provider
or other applications.
[0105] The term "probe unit" is used herein refer to a functionally
self-contained sub-system designed to carry out the required
analysis for a bearer, or for a pair or larger group of bearers.
Each probe unit may include separate modules to carry out such
operations as filtering the packets of interest and then
interpreting the actual packet or other data analysis.
[0106] In accordance with current trends, it is assumed in this
description that the links to be monitored carry Internet Protocol
(IP) traffic over passive optical networks (PONs) comprising
optical fibre bearers. Connection to such a network can only really
be achieved through use of passive optical splitters S1, S2 etc.
Passive splitters have advantages such as high reliability,
comparatively small dimensions, various connection configurations
and the fact that no power or element management resources
required. An optical splitter in such a situation works by paring
off a percentage of the optical power in a bearer to a test port,
the percentage being variable according to hardware
specifications.
[0107] A number of issues are raised when insertion of such a
device is considered. For example, there should be sufficient
bearer receiver power margins remaining at both test device and the
through port to the rest of the network. It becomes necessary to
consider what is the most economic method of monitoring the bearer
in the presence of a reduced test port power budget while limiting
the optical power needed by the monitoring probe and if the network
would have to be re-configured as a result of inserting the
device.
[0108] Consequently, inserting a power splitter to monitor a
network frequently requires an increase in launch power. This
entails upgrading the transmit laser assembly and installing an
optical attenuator where needed to reduce optical power into the
through path to normal levels. Such an upgrade would ideally only
be performed once.
[0109] For these reasons it is not desirable to probe, for example,
an ATM network more than once on any given bearer. Nevertheless, it
would be desirable to have the ability for multiple probing devices
to be connected to the same bearer, that is, have multiple outputs
from the optical interface. The different probes may be monitoring
different parameters. In addition, however, any network monitoring
system must offer a high degree of availability, and multiple
probes are desirable in the interests of redundancy. The probe
apparatuses and ancillary equipment described below allow the
implementation of such a network monitoring system which can be
maintained and expanded with simple procedures, with minimal
disruption to the network itself and to the monitoring
applications.
[0110] Network Probe System--General Architecture
[0111] FIG. 3 shows the basic functional architecture of a
multi-channel optical fibre telecommunications probe apparatus 50
combining several individual probe units, into a more flexible
system than has hitherto been available. The network monitoring
apparatus shown receives N bearer signals 70 such as may be
available from N optical fibre splitters. These enter a cross-point
switch 80 capable of routing each signal to any of M individual and
independently-replaceable probe units 90. Each probe unit
corresponds in functionality broadly with the unit 25 shown in FIG.
2. An additional external output 85 from the cross-point switch 80
is routed to an external connector. This brings important benefits,
as will described below.
[0112] The cross-point switch 80 and interconnections shown in FIG.
3 may be implemented using different technologies, for example
using passive optical or optoelectronic cross-points. High speed
networks, for example OC48, require electrical path lengths as
short as possible. An optical switch would therefore be desirable,
deferring as much as possible the conversion to electrical.
However, the optical switching technology is not yet fully mature.
Therefore the present proposal is to have an electrical
implementation for the cross-point switch 80, the signals converted
from optical to electrical at the point of entry into the probe
apparatus 50. The scale of an optoelectronic installation will be
limited by the complexities of the cross-point switch and size of
the probe unit. The choice of interconnect technology (for example
between electrical and optical), is generally dependent on signal
bandwidth-distance product. For example, in the case of high
bandwidth/speed standards such as OC3, OC12, or OC48, inter-rack
connections may be best implemented using optical technology.
[0113] Detailed implementation of the probe apparatus in a specific
embodiment will be described in more detail with reference to FIGS.
14 to 19. As part of this, a novel chassis arrangement for
multi-channel processing products is described, with reference to
FIGS. 15A-15C, which may find application in fields beyond
telecommunications monitoring. First, however, applications of the
multi-channel probe architecture will be described, with reference
to FIGS. 4 to 13.
[0114] FIG. 4 shows a simple monitoring application which can be
implemented using the apparatus of the type shown in FIG. 3. The
cross-point switch 80 is integrated into the probe chassis 100
together with up to four independently operating probe units. In
this implementation of the architecture each probe unit (90 in FIG.
3) is formed by a packet processor module 150 and single board
computer SBC 160 as previously described. There are provided two
packet processors 150 in each probe unit 90. Each packet processor
can receive and process the signal of one half-duplex bearer. SBC
160 in each probe unit has the capacity to analyse and report the
data collected by the two packet processors. Other modules included
in the chassis provide LAN interconnections for onward reporting of
results, probe management, power supply, and cooling modules (not
shown in FIGS. 4 to 13B).
[0115] In this application example a single, fully loaded chassis
100 is used with no redundancy to monitor eight single (four
duplex) bearers connected at 140 to the external optical inputs of
the apparatus (inputs 70-1 to 70-N in FIG. 3). The cross-point
switch external outputs 85 are shown but not used in this
configuration. Applications of these outputs are explained for
example in the description of FIGS. 6, 8, 10 and 12 below.
[0116] FIG. 5 shows an alternative application of the apparatus
giving 3+1 redundancy. Here three duplex bearer signals are applied
to external inputs 140 of the probe apparatus chassis 100, while
the fourth pair of inputs 142 is unused. Within the chassis there
are thus three primary probe units 90 plus a fourth, spare probe
unit 120. The cross-point switch 80 can be used to switch any of
the other bearers to this spare probe unit in the event of a
failure in another probe unit. Already by integrating the
cross-point switch and several probe units in a single chassis, a
scaleable packet processor redundancy down to 1:1 is achieved
without the overhead associated with an external cross-point
switch. Since electrical failures cause only a very minor
proportion of outages, redundancy within the chassis is valuable,
with the added bonus that complex wiring outside the chassis may be
avoided. One or more processors within each chassis can be spare at
a given time, and switched instantaneously and/or remotely if one
of the other probe units becomes inoperative.
[0117] FIG. 6 shows a larger redundant system comprising four
primary probe apparatuses (chassis 100-1 to 100-4), and a backup
chassis 130 which operates in the event of a failure in one of the
primary chassis. In this example of a large redundant system there
are 16 duplex bearers being monitored. Each external input pair of
the backup chassis is connected to receive a duplex bearer signal
from the external optical output 85 of a respective one of the
primary apparatuses 100-1 to 100-4. By this arrangement, in the
event of a single probe unit failure in one of the primary
apparatuses, a spare probe unit within the backup chassis can take
over the out-of-service unit's function. Assuming all inputs and
all of the primary probe units are operational in normal
circumstances, we may say that 4:1 redundancy is provided.
[0118] Recognising that in this embodiment only one optical
interface is connected to the bearer under test, the chassis
containing the optical interfaces can if desired have redundant
communications and/or power supply units (PSUs) and adopt a "hot
swap" strategy to permit rapid replacement of any hardware
failures. "Hot swap" in this context means the facility to unplug
one module of a probe unit within the apparatus and replace it with
another without interrupting the operation or functionality of the
other probe units. Higher levels of protection can be provided on
top of this, if desired, as described below with reference to FIGS.
15A-C and 16.
[0119] FIG. 7 shows a modified probe apparatus which provides an
additional optical input 170 to the cross-point switch 80. In other
words, the cross-point switch 80 has inputs for more bearer signals
than can be monitored by the probe units within its chassis. At the
same time, with the external optical outputs 85, the cross-point
switch 80 outputs for more signals than can be monitored by the
probe units within the chassis. These additional inputs 170 and
outputs 85 can be used to connect a number of probe chassis
together in a "daisy chain", to provide extra redundancy and/or
processing power. By default, in the present embodiment, copies of
the bearer signals received at daisy chain inputs 170 are routed to
the external outputs 85. Any other routing can be commanded,
however, either from within the apparatus or from outside via the
LAN (not shown).
[0120] FIG. 8 shows an example of daisy chaining the probe chassis
to give 8:1 redundancy. The four primary probe chassis 100-1 to
100-4 are connected in pairs (100-1 & 100-2 and 100-3 &
100-4). The external outputs 85 on the first chassis of each pair
are connected to the daisy chain inputs 170 on the second chassis.
The external outputs 85 of the second chassis are connected to
input of a spare of backup chassis 130 as before. These connections
can carry the signal through to the spare chassis when there has
been a failure in a probe unit in either the first or second
chassis in each pair. Unlike the arrangement of FIG. 6, however, it
will be seen that the backup chassis 130 still has two spare pairs
of external inputs. Accordingly, the system could be extended to
accommodate a further four chassis (up to sixteen further probe
units, and up to thirty-two further bearer signals), with the
single backup chassis 130 providing some redundancy for all of
them.
[0121] For applications that involve processor intensive tasks it
may be desirable to increase the processing power available to
monitor each bearer. This may be achieved by various different
configurations, and the degree of redundancy can be varied at the
same time to suit each application.
[0122] FIG. 9 illustrates how it is possible to increase the
processing power available for any given bearer by reconfiguring
the probe units. In this configuration only two duplex bearer
signals 140 are connected to the chassis 100. Two inputs 142 are
unused. Within the cross-point switch 80 each bearer signal is
duplicated and routed to two probe units 90. This doubles the
processing power available for each of the bearers 140. This may be
for different applications (for example routine billing and fraud
detection), or for more complex analysis on the same application.
Each packet processor (150, FIG. 4) and SBC (160) will be
programmed according to the application desired. In particular,
each packet processor, while receiving and processing all the data
carried by an associated bearer, will be programmed to filter the
data and to pass on only those packets, cells, or header
information which is needed by the SBC for a particular monitoring
task. The ability to provide redundancy via the external outputs 85
still remains.
[0123] FIG. 10 illustrates a second method of increasing processing
power is by connecting more than one chassis together in a daisy
chain or similar arrangement. Concerning the "daisy chain" inputs
170, FIG. 10 also illustrates how a similar effect can be achieved
using the unmodified apparatus (FIG. 3), providing the apparatus is
not monitoring its full complement of bearer signals. The external
inputs 140 can thus be connected to the external outputs 85 of the
previous chassis, instead of special inputs 170.
[0124] In the configuration of FIG. 10, two chassis 100-1 and 100-2
are fully loaded with four probe units 90 each. External signals
for all eight probe units are received at 140 from a single duplex
bearer. The cross-point switch 80 is used to replicate these
signals to every probe unit 90 within the chassis 100-1, and also
to the external outputs 85 of the first chassis 100-1. These
outputs in turn are connected to one pair of inputs 144 of the
second chassis 100-2. Within the second chassis, the same signals
are replicated again and applied to all four probe units, and
(optionally) to the external outputs 85 of the second chassis
100-2.
[0125] Thus, all eight probe units are able to apply their
processing power to the same pair of signals, without tapping into
the bearer more than once. By adding further chassis in such a
daisy chain, processing power is scaleable practically to as much
processing power as needed.
[0126] The examples given are for way of illustration only, showing
how using the chassis architecture described it is possible to
provide the user with the processing power needed and the
redundancy to maintain operation of the of the system in the event
of faults and planned outages. It will be appreciated that there
are numerous different configurations possible, besides those
described.
[0127] For example, it is also possible to envisage a bidirectional
daisy chain arrangement. Here, one output 85 of a first chassis
might be connected to one input 170 of a second chassis, while the
other output 85 is connected to an input 170 of a third chassis.
This arrangement can be repeated if desired to form a
bi-directional ring of apparatuses, forming a kind of "optical
bus".
[0128] The probe apparatus described above allow the system
designer to achieve N+1 redundancy by using the cross-point switch
80 to internally re-route a bearer to a spare processor, or to
another chassis. On the other hand, it will be recognised that some
types of failure (e.g. in the chassis power supply) will disrupt
operation of all of the processors in the chassis. It is possible
to reduce such a risk by providing N+1 PSU redundancy, as will
be/has been described.
[0129] Broadband Bridging Isolator
[0130] FIG. 11 shows an optional signal replicating device for use
in conjunction with the probe apparatus described above, or other
monitoring apparatus. This device will be referred to as a
Broadband Bridging Isolator (BBI). Broadband Bridging Isolator can
be scaled to different capacities, and to provide additional fault
tolerance independently of the probe apparatuses described above.
The basic unit comprises a signal replicator 175. For each unit, an
(optical) input 176 is converted at 177 to an electrical signal,
which is then replicated and converted at 179 etc. to produce a
number of identical optical output signals at outputs 178-1
etc.
[0131] Also provided within BBI 172 are one or more standby
selectors (multiplexers) 180 (one only shown). Each selector 180
receives replicas of the input signals and can select from these a
desired one to be replicated at a selector optical output 182. An
additional input 186 (shown in broken lines) may be provided which
passes to the selector 180 without being replicated, to permit
"daisy chain" connection.
[0132] In use, BBI 172 takes a single tap input 176 from a bearer
being monitored and distributes this to multiple monitoring
devices, for example probe apparatuses of the type shown in FIGS. 3
to 10. For reliability, the standby selector 180 allows any of the
input signals to be switched to a standby chassis.
[0133] The number of outputs that are duplicated from each input is
not critical. A typical implementation may provide four, eight or
sixteen replicators 175 in a relatively small rack mountable
chassis, each having (for example) four outputs per input. Although
the concepts here are described in terms of optical bearers, the
same concepts could be applied to high speed electrical bearers
(e.g. E3, DS3 and STM1e).
[0134] The reasons for distributing the signal could be for
multiple applications, duplication for reliability, load sharing or
a combination of all three. It is important that only one tap need
be made in the operational bearer. As described in the introductory
part of this specification, each optical tap reduces the strength
of the optical signal reaching the receiver. In marginal
conditions, adding a tap may require boosting the signal on the
operational bearer. Network operators do not want to disrupt their
operational networks unless they have to. The BBI allows different
monitoring apparatuses for different applications to be connected,
and removed and re-configured without affecting the operational
bearer, hence the name "isolator". The BBI can even be used to
re-generate this signal by feeding one of the outputs back into the
network, so that the BBI becomes part of the operational
network.
[0135] The number of bearer signals that are switched through the
standby selector 180 will depend on the users requirements--this
number corresponds effectively to "N" in the phrase "N+1
redundancy". The number of standby selectors in each BBI is not
critical. Adding more means that more bearers can be switched
should there be a failure.
[0136] The BBI must have high reliability as when operational in a
monitoring environment it an essential component in the monitoring
of data, providing the only bridging link between the signal
bearers and the probe chassis. No digital processing of the bearer
signal is performed in the BBI, which can thus be made entirely of
the simplest and most reliable optoelectronic components. When
technology permits, in terms of cost and reliability, there may be
an "all-optical" solution, which avoids conversion to electrical
form and back to optical. Presently, however, the state of the art
favours the optoelectronic solution detailed here. The BBI can be
powered from a redundant power supply to ensure continuous
operation. The number of bearers handled on a single card can be
kept small so that in event of a failure the number of bearers
impacted is small. The control of the standby switch can be by an
external control processor.
[0137] FIG. 12 shows a system configuration using BBIs and two
separate probe chassis 100-1 and 100-2 implementing separate
monitoring applications. The two application chassis may be
operated by different departments within the network operators
organisation. A third, spare probe chassis 130 is shared in a
standby mode. This example uses two BBIs 172 to monitor a duplex
bearer pair shown at L1, L2, and other bearers not shown. Splitters
S1 and S2 respectively provide tap input signals from L1, L2 to the
inputs 176 of the separate BBIs. Each BBI duplicates the signal at
its input 176 to two outputs 178, and the manner described above
with reference to FIG. 11. For improved fault tolerance, the two
four-way BBIs 172 are used to half duplex bearers L1 and L2
separately. In other words, the two halves of the same duplex
bearer are handled by different BBIs. Three further duplex bearers
(L3-L8, say, not shown in the drawing), are connected to the
remaining inputs of the BBIs 172 in a similar fashion.
[0138] Using the standby selector 180 any one of the bearers can be
switched through to the standby chassis 130 in the event of a
failure of a probe unit in one of the main probe chassis 100-1,
100-2. It will be appreciated that, if there is a failure of a
complete probe chassis, then only one of the bearers can be
switched through to the standby probe. In a larger system with,
say, 16 duplex bearers, four main probe chassis and two standby
chassis, the bearers distributed by each BBI can be shared around
the probe chassis so that each probe chassis processes one bearer
from each BBI. Then all four bearers can be switched to the standby
probe in the event of a complete chassis failure.
[0139] It will be seen that the BBI offers increased resilience for
users particularly when they have multiple departments wanting to
look at the same bearers. The size of the BBI used is not critical
and practical considerations will influence the number of inputs
and outputs. For example, the BBI could provide inputs for 16
duplex bearers, each being distributed to two or three outputs with
four standby outputs. Where multiple standby circuits are used each
will be capable of being independently switched to any of the
inputs.
[0140] FIGS. 13A and 13B illustrate a process of upgrading the
processing power of a network monitoring system without
interrupting operation, using the facilities of the replicating
devices (BBIs 172) and probe chassis described above. FIG. 13A
shows an example of an "existing" system with one probe chassis
100-1. Four duplex bearer signals are applied to inputs 140 of the
chassis. Via the internal cross-point switch 80, each bearer signal
is routed to one probe unit 90. With a view to further upgrades and
fault tolerance, a broadband bridging isolator (BBI). Each bearer
signal is received from a tap in the actual bearer (not shown) at a
BBI input 176. The same bearer signal is replicated at BBI outputs
178-1, 178-2 etc. The first set of outputs 178-1 are connected to
the inputs 140 of the probe chassis. The second set of outputs
178-2 are not used in the initial configuration.
[0141] FIG. 13B shows the an expanded system, which includes a
second probe chassis 100-2 also loaded with four probe units 90.
Consequently there are now provided two probe units per bearer,
increasing the processing power available per bearer. It is a
simple task to migrate from the original configuration in FIG. 13A
to the new one shown in FIG. 13B:
[0142] Step 1--Install the extra chassis 100-2 with the probe
units, establishing the appropriate power supply and LAN
communications.
[0143] Step 2--Connect two of the duplicate BBI outputs 186 to
inputs of the extra chassis 100-2. (All four could be connected for
redundancy if desired.)
[0144] Step 3--Configure the new chassis 100-2 and probe units to
monitor the two bearer signals in accordance with the desired
applications.
[0145] Step 4--Re-configure the original chassis to cease
monitoring the corresponding two bearer signals of the first set of
outputs 178-1 (188 in FIG. 13B). (The processing capacity freed in
the original chassis 100-1 can then be assigned expanded monitoring
of the two duplex bearer signals which remain connected to the BBI
outputs 178-1.)
[0146] Step 5--Remove the connections 188 no longer being used.
(These connections could be left for redundancy if desired.)
[0147] In this example the processing power has been doubled from
one probe unit per bearer to two probe units per bearer but it can
be seen that such a scheme could be easily extended by connecting
further chassis. At no point has the original monitoring capacity
been lost, and at no point have the bearers themselves (not shown)
been disrupted. Thus, for example, a module of one probe unit can
be removed for upgrade while other units continue their own
operations. If there is spare capacity, one of the other units can
step in to provide the functionality of the unit being replaced.
After Step 2, the entire first chassis 100-1 could be removed and
replaced while the second chassis 100-2 steps in to perform its
functions. Variations on this method are practically infinite, and
can also be used for other types of migration, such as when
increasing system reliability.
[0148] The hardware and methods used in these steps can be arranged
to comply with "hot-swap" standards as defined earlier. The system
of FIGS. 13A and 13B, and of course any of the systems described
above, may further provide automatic sensing of the removal (or
failure) of a probe unit (or entire chassis), and automatic
re-configuration of switches and re-programming of probe units to
resume critical monitoring functions with minimum delay.
Preferably, of course, the engineer would instruct the
re-programming prior to any planned removal of a probe unit module.
A further level of protection, which allows completely
uninterrupted operation with minimum staff involvement, is to sense
the unlocking of a processing card prior to actual removal, to
reconfigure other units to take over the functions of the affected
module, and then to signal to the engineer that actual removal is
permitted. This will be illustrated further below with reference to
FIG. 15A.
[0149] Multi-channel Probe Apparatus--Functional arrangement
[0150] FIG. 14 is a functional block schematic diagram of a
multi-channel probe apparatus suitable for implementing the systems
shown in FIGS. 4 to 13A and 13B. Like numerals depict like
elements. All of the modules shown in FIG. 14 and their
interconnections are ideally separately replaceable, and housed
within a self-contained enclosure of standard rack-mount
dimensions. The actual physical configuration of the network probe
unit modules in a chassis with special backplane will be described
later.
[0151] A network interface module 200 provides optical fibre
connectors for the incoming bearer signals EXT 1-8 (70-1 to 70-N in
FIG. 3), and performs optical to electrical conversion. A
cross-point switch 80 provides a means of linking these connections
to appropriate probe units 90. Each input of a probe unit can be
regarded as a separate monitoring channel CH1, CH2 etc. As
mentioned previously, each probe unit may in fact accept plural
signals for processing simultaneously, and these may or may not be
selectable independently, or grouped into larger monitoring
channels. Additional optical outputs EXT 9,10 are provided to act
as "spare" outputs (corresponding to 85 in FIG. 4)In the
embodiment, each probe unit 90 controls the cross-point switch 80
to feed its inputs (forming channel CH1, 2, 3 or 4 etc.)with a
bearer signal selected from among the incoming signals EXT 1-8.
This selection may be pre-programmed in the apparatus, or may be
set by remote command over a LAN. Each probe unit (90) is
implemented in two parts, which may conveniently be realised as a
specialised packet processor 150 and a general purpose single board
computer SBC 160 module. There are provided four packet processors
150 to 150 each capable of filtering and pre-processing eight half
duplex bearer signals at full rate, and four SBCs 160 capable of
further processing the results obtained by the packet processors.
The packet processors 150 comprise dedicated data processing
hardware, while the SBC can be implemented using industry standard
processors or other general purpose processing modules. The packet
processors 150 are closely coupled by individual peripheral buses
to their respective SBCs 160 so as to form self-contained
processing systems, each packet processor acting as a peripheral to
its "host" SBC. Each Packet Processor 150 carries out a high speed
time critical cell and packet processing including data aggregation
and filtering. A second level of aggregation is carried out in the
SBC 160.
[0152] LAN and chassis management modules 230, 235 (which in the
implementation described later are combined on a single card)
provide central hardware platform management and onward
communication of the processing results. For this onward
communication, multiple redundant LAN interfaces are provided
between every SBC 160 and the LAN management module 230 across the
backplane. The LAN management function has four LAN inputs (one
from each SBC) and four LAN outputs (for redundancy) to the
monitoring LAN network. Multiple connections are provided as
different SBC manufacturers use different pin connectors on their
connectors. For any particular manufacturer there is normally only
one connection between the SBC 160 and the LAN management module
230. The dual redundant LAN interfaces are provided for reliability
in reporting the filtered and processed data to the next level of
aggregation (site processor 40 in FIG. 2). This next level can be
located remotely. Each outgoing LAN interface is connectable to a
completely independent network, LANA or LANB to ensure reporting in
case of LAN outages. In case of dual outages, the apparatus has
buffer space for a substantial quantity of reporting data.
[0153] The chassis management module 235 oversees monitoring and
wiring functions via (for example) an I.sup.2C bus using various
protocols. Although I.sup.2C is normally defined as a shared bus
system, each probe unit for reliability has its own I.sup.2C
connection direct to the management module. The management module
can also instruct the cross-point switch to activate the "spare"
output (labelled as monitoring channels CH9,10 and optical outputs
EXT 9,10) when it detects failure of one of the probe unit modules.
This operation can also be carried out under instruction via
LAN.
[0154] The network probe having the architecture described above
must be realised in a physical environment capable of fulfilling
the functional specifications and other hardware platform
considerations such as the telecommunications environment it is to
be deployed in. A novel chassis (or "cardcage") configuration has
been developed to meet these requirements within a compact
rack-mountable enclosure. The chassis is deployed as a fundamental
component of the data collection and processing system.
[0155] Multi-channel Probe Apparatus--Physical Implementation
[0156] FIGS. 15A, B and C show how the probe architecture of FIG.
14 can be implemented with a novel chassis, in a particularly
compact and reliable manner. To support the network probe
architecture for this embodiment there is also provided a custom
backplane 190. FIG. 16 shows which signals are carried by the
backplane, and which modules provide the external connections.
Similar reference signs are used as in FIG. 14, where possible.
[0157] Referring to FIG. 16 for an overview of the functional
architecture, the similarities with the architecture of FIG. 14
will be apparent. The network probe apparatus again has eight
external optical terminals for signals EXT 1-8 to be monitored.
These are received at a network interface module 200. A cross-point
switch module 80 receives eight corresponding electrical signals
EXT 1'-8' from module 200 through the backplane 190. Switch 80 has
ten signal outputs, forming eight monitoring channels CH1-8 plus
two external outputs (CH9,10). Four packet processor modules 150-1
to 150-4 receive pairs of these channels CH1,2, CH3,4 etc.
respectively. CH9,10 signals are fed back to the network interface
module 200, and reproduced in optical form at external terminals
EXT 9,10. All internal connections just mentioned are made through
the backplane via transmission lines in the backplane 190. Each
packet processor is paired with a respective SBC 160-1 to 160-4 by
individual cPCI bus connections in the backplane.
[0158] A LAN & Chassis Management module 230 is provided, which
is connected to the other modules by I.sup.2C buses in the
backplane, and by LAN connections. A LAN interface module 270
provides external LAN connections for the onward reporting of
processing results. Also provided is a fan assembly 400 for cooling
and a power supply (PSU) module 420.
[0159] Referring to the views in FIG. 15A chassis 100 carries a
backplane 190 and provides support and interconnections for various
processing modules. Conventionally, the processing modules are
arranged in slots to the "front" of the backplane, and space behind
the backplane in a telecommunications application is occupied by
specialised interconnect. This specialised interconnect may include
further removable I/O cards referred to as "transition cards". The
power supply and fans are generally located above and/or below the
main card space, and the cards (processing modules) are arranged
vertically in a vertical airflow. These factors make for a very
tall enclosure, and one which is far deeper than the ideals of 300
mm or so in the NEBS environment. The present chassis features
significant departures from the conventional design, which result
in a compact and particularly shallow enclosure.
[0160] In the present chassis, the power supply module (PSU) 420 is
located in a shallow space behind the backplane 190. The processing
modules 150-1, 160-1 etc. at the front of the backplane are,
moreover, arranged to lie horizontally, with their long axes
parallel to the front panel. The cooling fans 400 are placed to one
side of the chassis. Airflow enters the chassis at the front at 410
and flows horizontally over the components to be cooled, before
exiting at the rear at 412. This arrangement gives the chassis a
high cooling capability while at the same time not extending the
size of the chassis beyond the desired dimensions. The outer
dimensions and front flange of the housing allow the chassis to be
mounted on a standard 19 inch (483 mm) equipment rack, with just 5U
height. Since the width of the enclosure is fixed by standard rack
dimensions, but the height is freely selectable, the horizontal
arrangement allows the space occupied by the enclosure to be
matched to the number of processor slots required by the
application. In the known vertical orientation, a chassis which
provides ten slots must be just as high as one which provides
twenty slots, and additional height must be allowed for airflow
arrangements at top and bottom.
[0161] Referring also to FIGS. 15B and 15C, there are ten card
slots labelled F1-F10 on the front side of the backplane 190. There
are two shallow slots B1 and B2 to the rear of the backplane 190,
back-to back with F9 and F10 respectively. The front slot
dimensions correspond to those of the cPCI standard, which also
defines up to five standard electrical connectors referred to
generally as J1 to J5,as marked in FIGS. 15B and 15C. It will be
known to the skilled reader that connectors J1 and J2 have 110 pins
each, and the functions of these are specified in the cPCI standard
(version PICMG 2.0 R2.1 (May 1st 1998)).
[0162] Other connector positions are used differently by different
manufacturers. Eight of the front slots (F1-F8) support the Packet
Processor/SBC cards in pairs. The cards are removable using `hot
swap` techniques, as previously outlined, using thumb levers 195 to
lock/unlock the cards and to signal that a card is to be
inserted/removed. The other two front slots F9 and F10 are used for
cross-point switch 80 and LAN/Management card 230 respectively.
Slots F1 to F8 comply with the cPCI insofar as connectors J1, J2,
J3 and J5 are concerned. Other bus standards such as VME could be
also be used. The other slots F9 and F10 are unique to this design.
All of the cPCI connections are standard and the connectivity,
routing and termination requirements are taken from the cPCI
standard specification. Keying requirements are also taken from the
cPCI standard. The cPCI bus does not connect all modules, however:
it is split into four independent buses CPCI1-4 to form four
self-contained host-peripheral processing sub-systems. Failure of
any packet processor/SBC combination will not affect the other
three probe units.
[0163] Each of the cards is hot-swappable and will automatically
recover from any reconfiguration. Moreover, by providing switches
responsive to operation of the thumb levers 195, prior to physical
removal of the card, the system can be warned of impending removal
of an module. This warning can be used to trigger automatic
re-routing of the affected monitoring channel(s). The engineer
replacing the card can be instructed to await a visual signal on
the front panel of the card or elsewhere, before completing the
removal of the card. This signal can be sent by the LAN/Management
module 270, or by a remote controlling site. This scheme allows
easy operation for the engineer, without any interruption of the
monitoring functions, and without special steps to command the
re-routing. Such commands might otherwise require the co-ordination
of actions at the local site with staff at a central site, or at
best the same engineer might be required to move between the
chassis being worked upon and a nearby PC workstation.
[0164] As mentioned above, the upper two front slots (F10, F9) hold
the LAN & Management module 230 and the cross-point switch 80
respectively. Slot B1 (behind F9) carries a Network Transition card
forming network interface module 200, while the LAN interface 270
in slot B2 (behind F10) carries the LAN connectors. All external
connections are to the apparatus are provided by special transition
cards in these rear slots, and routed through the backplane. No
cabling needs to reach directly the rear of the individual probe
unit slots. No cabling at all is required to the front of the
enclosure. This is not only tidy externally of the housing, but
leaves a clear volume behind the backplane which can be occupied by
the PSU 420, shown cut-away in FIG. 15C, yielding a substantial
space saving over conventional designs and giving greater ease of
maintenance. The rear slot positions B1, B2 are slightly wider, to
accommodate the PSU connectors 422.
[0165] The J4 position in the backplane is customised to route high
integrity network signals (labelled "RF" in FIG. 15B). These are
transported on custom connections not within cPCI standards. FIG.
15B shows schematically how these connectors transport the bearer
signals in monitoring channels CHI etc. from the cross-point switch
80 in slot F9 to the appropriate packet processors 150-1 etc. in
slots F2, F4, F6, F8. The external bearer signals EXT1'-8' in
electrical form can be seen passing through the backplane from the
cross-point switch 80 (in slot F9) to the network interface module
200 (B1). These high speed, high-integrity signals are carried via
appropriately designed transmission lines in the printed wiring of
the backplane 190. The variation in transmission delay between
channels in the chassis is not significant for the applications
envisaged. However, in order to avoid phase errors it is still
important to ensure that each half of any differential signal is
routed from its source to its destination using essentially equal
delays. To ensure this, the delays must be matched to the packet
processors for each set for the backplane and cross-point switch
combination. It is important to note that these monitoring channels
are carried independently on point-to point connections, rather
than through any shared bus such as is provided in the H.110
protocol for computer telephony.
[0166] The backplane also carries I.sup.2C buses (SMB protocol) and
the LAN wiring. These are carried to each SBC 160-1 etc. either in
the J3 position or the J5 position, depending on the manufacturer
of the particular SBC, as described later. The LAN interface module
270 provides the apparatus with two external LAN ports for
communications to the next layer of data processing/aggregation,
for example a site processor.
[0167] Connectivity is achieved using two LANs (A and B) at 100
BaseT for a cardcage. The LAN I/O can be arranged to provide
redundant connection to the external host computer 40. This may be
done, for example, by using four internal LAN connection and four
external LAN connections routed via different segments of the LAN
60. It is therefore possible to switch any SBC to either of the LAN
connections such that any SBC may be on any one connection or split
between connections. This arrangement may be changed dynamically
according to circumstances, as in the case of an error occurring,
and allows different combinations of load sharing and redundancy.
Additionally, this allows the probe processors to communicate with
each other without going on the external LAN. However, this level
of redundancy in the LAN connection cannot be achieved if the total
data from the probe processors exceeds the capacity of any one
external LAN connection.
[0168] An external timing port (not shown in FIG. 16) is
additionally provided for accurately time-stamping the data in the
packet processor. The signal is derived from any suitable source,
for example a GPS receiver giving a 1 pulse per second input. It is
also possible to generate this signal using one of the Packet
Processor cards, where one Packet Processor becomes a master card
and the others can synchronise to it.
[0169] The individual modules will now be described in detail, with
reference to FIGS. 17 19. This will further clarify the
inter-relationships between them, and the role of the backplane 190
and chassis 100.
[0170] Cross-Point Switch Module 80
[0171] FIG. 17 is a block diagram of the cross-point switch 80 and
shows also the network line interfaces 300 (RX) and 310 (TX)
provided on the network interface module 200. There are eight
optical line receiver interfaces 300 provided within module 200.
There are thus eight bearer signals which are conditioned on the
transition card (module 200) and transmitted in electrical form
EXT1'-8.varies. directly through the backplane 190 to the
cross-point switch card 80. Ten individually configurable
multiplexers (selectors) M are provided, each freely selecting one
of the eight inputs. Each monitoring channel (CH1-8) and hence each
packet processor 150 can receive any of the eight incoming network
signals (EXT1'-8').
[0172] The outputs to the packet processors (CH1-CH4) are via the
backplane 190 (position J4, FIG. 15B as described above) and may
follow, amongst others, DS3/OC3/OC12/OC48 electrical standards or
utilise a suitable proprietary interface. Each packet processor
module 150 controls its own pair of multiplexers M directly.
[0173] The external optical outputs EXT 9,10 are provided via
transmit interface 310 of the module 200 for connecting to a spare
chassis (as in FIG. 8). These outputs can be configured to be any
of the eight inputs, using a further pair of multiplexers M which
are controlled by the LAN/Management Module 230. In this way, the
spare processor or chassis 130 mentioned above can be activated in
case of processor failure. In an alternative implementation, the
selection of these external output signals CH9 and CH10 can be
performed entirely on the network interface module 200, without
passing through the backplane or the cross-point switch module
80.
[0174] Although functionally each multiplexer M of the cross-point
switch is described and shown as being controlled by a respective
packet processor 150, in the present embodiment this control is
conducted via the LAN & management module 230. Commands or
requests for a particular connection can be sent to the LAN &
management module from the packet processor (or associated SBC 160)
via the LAN connections, or I.sup.2C buses, provided in connectors
J3 or J5.
[0175] Packet Processor Module 150
[0176] FIG. 18 is a block diagram of one of the Packet Processor
modules 150 of the apparatus. The main purpose of packet processor
(PP) 150 is to capture data from the network interface. This data
is then processed, analysed and filtered before being sent to a SBC
via a local cPCI bus. Packet processor 150 complies with Compact
PCI Hot Swap specification PICMG-2.1 R 1.0, mentioned above. Packet
Processor 150 here described is designed to work up to 622 Mbits/s
using a Sonet/SDH frame structure carrying ATM cells using AAL5
Segmentation And Reassembly (SAR). Other embodiments can be
employed using the same architecture, for example to operate at
OC48 (2.4 Gbit.s.sup.-1).
[0177] The following description makes reference to a single "half"
of the two-channel packet processor module 150, and to a single
Packet Processor/SBC pair only (single channel). The chassis as
described supports four such Packet Processor/SBC pairs, and each
packet processor comprises two processing means to handle multiple
bearer signals (multiple monitoring channels).
[0178] It is possible for the Packet Processor 150 to filter the
incoming data. This is essential due to the very high speed of the
broadband network interfaces being monitored, such as would be the
case for OC-3 and above. The incoming signals are processed by the
Packet Processor, this generally taking the form of time stamping
the data and performing filtering based on appropriate fields in
the data. Different fields can be chosen accordingly, for example
ATM cells by VPI/NVCI (VC) number, IP by IP address, or filtering
can be based on other, user defined fields. It is necessary to
provide the appropriate means to recover the clock and data from
the incoming signal, as the means needed varies dependent on link
media and coding schemes used. In a typical example using ATM, ATM
cells are processed by VPI/NVCI (VC) number. The Packet Processor
is provided with means 320 to recover the clock and data from the
incoming signal bit stream. The data is then `deframed` at a
transmission convergence sub-layer 330 to extract the ATM cells.
The ATM cells are then time-stamped 340 and then buffered in a
First In First Out (FIFO) buffer 350 to smooth the rate of burst
type data. Cells from this FIFO buffer are then passed sequentially
to an ATM cell processor 360. The packet processor can store ATM
cells to allow it to re-assemble cells into a message--a Protocol
Data Unit (PDU). Only when the PDU has been assembled will it be
sent to the SBC. Before assembly, the VC of a cell is checked to
ascertain what actions should be taken, for example, to discard
cell, assemble PDU, or pass on the raw cell.
[0179] Data is transferred into the SBC memory using cPCI DMA
transfers to a data buffer 38. This ensures the very high data
throughput that may be required if large amounts of data are being
stored. The main limitation in the amount of data that is processed
will be due to the applications software that processes it. It is
therefore the responsibility of the Packet Processor 150 to carry
out as much pre-processing of the data as possible so that only
that data which is relevant is passed up into the application
domain.
[0180] The first function of the Packet Processor 150 is to locate
the instructions for processing the VC (virtual channel or ) to
which the cell belongs. To do this it must convert the very large
VPI/VCI of the cell into a manageable pointer to its associated
processing instructions (VC # key). This is done using a hashing
algorithm by hash generator 390, which in turn uses a VC hash
table. Processor 150, having located the instructions, can then
process the cell.
[0181] Processing the cell involves updating status information for
the particular VC (e.g. cell count) and forwarding the cell and any
associated information (e.g. "Protocol Data Unit (PDU) received")
to the SBC 160 if required. By reading the status of a particular
VC, the processor can vary its action depending on the current
status of that VC (e.g. providing summary information after first
cell received). Cell processor 360 also requires certain
configurable information which is applicable to all of its
processing functions regardless of VC (e.g. buffer sizes) and this
`global` configuration is accessible via a global configuration
store.
[0182] A time stamping function 340 can be synchronised to an
external GPS time signal or can be adjusted by the SBC 160. The SBC
can also configure and monitor the `deframer` (e.g. set up frame
formats and monitor alarms) as well as select the optical inputs
(EXT 1-8) to be monitored. Packet Processor 150 provides all of the
necessary cPCI interface functions.
[0183] Each packet processor board 150-1 etc. is removable without
disconnecting power from the chassis. This board will not impact
the performance of other boards in the chassis other than the
associated SBC. The microprocessor notifies the presence or absence
of the packet processor and processes any signal loss conditions
generated by the Packet Processor.
[0184] Single Board Computer (SBC) Modules 160
[0185] The SBC module 160 is not shown in detail herein, being a
general-purpose processing module, examples including the Motorola
CPV5350, FORCE CPCI-730, and SMT NAPA. The SBC 150 is a flexible,
programmable device. In this specific embodiment two such devices
may exist on one cPCI card, in the form of "piggyback" modules
(PMCs). The 100 BaseT interfaces, disk memory etc. may also be in
the form of PMCs. As already described, communications via the cPCI
bus (J1/J2) on the input side and via the LAN port on the output
side and all other connections are via the backplane at the rear,
unless for diagnostic purposes for which an RS-232 port is provided
at the front.
[0186] LAN & Chassis Management Module 230
[0187] FIG. 19 is a block diagram of the combined LAN and chassis
management card for the network probe as has been described. Module
230 performs a number of key management functions, although the
probe units 150/160 can be commanded independently from a remote
location, via the LAN interface. The card firstly provides a means
for routing probe units SMB and LAN connections, including dual
independent LAN switches 500A and 500B to route the LAN connections
with redundancy and sufficient bandwidth to the outside world.
[0188] On the chassis management side, a Field Programmable Gate
Array (FGPA) 510 within this module performs the following
functions:
[0189] (520) I.sup.2C and SMB communications, with reference to
chassis configuration storage registers 530
[0190] (540) `magic packet` handling, for resetting the modules
remotely in the event that the higher level network protocols "hang
up";
[0191] (550) environmental control and monitoring of fan speed and
PSU & CPU temperatures functions to ensure optimal operating
conditions for the chassis, and preferably also to minimise
unnecessary power consumption and fan noise;
[0192] A hardware watchdog feature 560 is also included to monitor
the activity of all modules and take appropriate action in the
event that any of them becomes inactive or unresponsive. This
includes the ability to reset modules.
[0193] Finally, the management module implements at 580
"Multivendor Interconnect", whereby differences in the usage of
cPCI connectors pins (or whatever standard is adopted) between a
selection of processor vendors can be accommodated.
[0194] As mentioned previously, the chassis carries at some
locations, cPCI processor modules from a choice of selected
vendors, but these are coupled via cPCI bus to special peripheral
cards. While such cards are known in principle, and the
processor-peripheral bus is fully specified, the apparatus
described does not have a conventional interconnect arrangement for
the broadband signals, multiple redundant LAN connections and so
forth. Even for the same functions, such as the LAN signals and
I.sup.2C/SMB protocol for hardware monitoring, different SBC
vendors place the relevant signals on different pins of the cPCI
connector set, particularly they may be on certain pins in J3 with
some vendors, and on various locations in J5 with others.
Conventionally, this means that system designer has to restrict the
user's choice of SBC modules to those of one vendor, or a group of
vendors who have adopted the same pin assignment for LAN and SMB
functions, besides the standard assignments for J1, and J2 which
are specified for all cPCI products.
[0195] To overcome this obstacle a modular Multivendor Interconnect
(MVI) solution may be applied. The MVI module 580 is effectively
four product-specific configuration cards that individually route
the LAN and SMB signals received from each SBC 160-1 etc. to the
correct locations on the LAN/Management cards. One MVI card exists
for each processor. These are carried piggyback on the
LAN/management module 230, and each is accessible from the front
panel of the enclosure. The backplane in locations J3 and J5
includes sufficient connectors, pins and interconnections between
the modules to satisfy a number of different possible SBC types.
Needless to say, when replacing a processor card with one of a
different type, the corresponding MVI configuration card needs
exchanging also.
[0196] An alternative scheme to switch the card connection
automatically based on vendor ID codes read via the backplane can
also be envisaged. In a particular embodiment, for example, the
"Geographic Address" pins defined in the cPCI connector
specifications may be available for signalling (under control of a
start-up program) which type of SBC 160 is in a given slot. The
routing of SMB, LAN and other signals can then be switched
electronically under control of programs in the LAN &
management card 230.
Conclusion
[0197] Those skilled in the art will recognise that the invention
in any of its aspects is not limited to the specific embodiments
disclosed herein. In particular, unless specified in the claims,
the invention is in no way limited to any particular type of
processor, type of network to be monitored, protocol, choice of
physical interconnect, choice of peripheral bus (cPCI v. VME,
parallel v. serial etc.), number of bearers per chassis, number of
bearers per monitoring channel, number of monitoring channels per
probe unit.
[0198] The fact that independent processor subsystems are arranged
in the chassis allows multiple data paths from the
telecommunications network to the LAN network, thereby providing
inherent redundancy. On the other hand, for other applications such
as computer telephony, reliability and availability may not be so
critical as in the applications addressed by the present
embodiment. For such applications, a similar chassis arrangement
but with H.110 bus in the backplane may be very useful. Similarly,
the cPCI bus, I.sup.2C bus and/or LAN interconnect may be shared
among all the modules,
[0199] Each aspect of the invention mentioned above is to be
considered as independent, such that the probe functional
architecture can be used irrespective of the chassis configuration,
and vice versa. On the other hand, the reader will recognise that
the specific combinations of these features offers in a highly
desirable instrumentation system, which provides the desired
functionality, reliability and availability levels in a compact and
scalable architecture.
[0200] In the specific embodiments described herein, each probe
unit comprising first and second processor modules (the packet
processor and SBC respectively) is configured to monitor simplex
and duplex bearers. The invention, in any of its aspects, is not
limited to such embodiments. In particular, each probe unit may be
adapted to process one or more individual bearer signals. In the
case of lower speed protocol signals the bearer signals can be
multiplexed together (for example within the cross-point switch
module 80 or network interface module 200) to take full advantage
of the internal bandwidth of the architecture.
* * * * *