U.S. patent application number 11/190811 was filed with the patent office on 2006-03-23 for multi-service transport apparatus for integrated transport networks.
This patent application is currently assigned to ALCATEL. Invention is credited to Silvano Frigerio, Marco Lenti, Alberto Lometti.
Application Number | 20060062246 11/190811 |
Document ID | / |
Family ID | 34931405 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060062246 |
Kind Code |
A1 |
Lometti; Alberto ; et
al. |
March 23, 2006 |
Multi-service transport apparatus for integrated transport
networks
Abstract
A multi-service transport apparatus for integrated transport
networks is described. The apparatus comprises an electrical
matrix, termination function means handling signals incoming at
said apparatus input, a plurality of termination function means
interfacing different layers, and adaptation function means. The
termination function means handling incoming signals are
implemented in input/output port devices; the termination function
means interfacing different layers and said adaptation function
means are implemented in adapter devices. According to the present
invention, the matrix performs exclusively the switching of the
incoming signals that are already terminated and adapted by said
input/output port devices and by said adapter devices and it is
transparent with respect to the signal format.
Inventors: |
Lometti; Alberto; (Merate
(Lecco), IT) ; Frigerio; Silvano; (Cantu' (Como),
IT) ; Lenti; Marco; (Monza, IT) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
ALCATEL
|
Family ID: |
34931405 |
Appl. No.: |
11/190811 |
Filed: |
July 28, 2005 |
Current U.S.
Class: |
370/465 |
Current CPC
Class: |
H04L 49/1523 20130101;
H04L 49/351 20130101; H04L 49/602 20130101 |
Class at
Publication: |
370/465 |
International
Class: |
H04J 3/16 20060101
H04J003/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2004 |
EP |
04 292 277.3 |
Claims
1. A multi-service apparatus (P) for an integrated transport
network which comprises a plurality of signal layers, said
apparatus (P) comprising an electrical matrix (M), termination
function means (60') handling signals incoming at apparatus inputs,
a plurality of termination function means (60) interfacing
different layers, and adaptation function means (61), wherein said
termination function means (60') handling incoming signals are
implemented in input/output port devices (PD), further wherein said
termination function means (60) interfacing different layers and
said adaptation function means (61) are implemented in adapter
devices (AD), further wherein said matrix (M) performs exclusively
the switching of the incoming signals that are already terminated
and adapted by said input/output port devices (PD) and by said
adapter devices (AD) and it is transparent with respect to signal
format.
2. The apparatus according to claim 1, wherein a separate adapter
device (AD) is provided for at least one pair of termination and
adaptation function means (60, 61) between adjacent layers.
3. The apparatus according to claim 2, wherein said adjacent layers
are selected from the group consisting of: Ethernet layer
(L2)--Multi Protocol Label Switching layer (MPLS); Multi Protocol
Label Switching layer (MPLS)--Resilient Packet Ring layer (RPR);
Resilient Packet Ring layer (RPR)--SDH Lower Order layer (LPC); SDH
Lower Order layer (LPC)--SDH Higher Order layer (HPC); and SDH
Higher Order layer (HPC)--Optical Data Unit layer (ODU).
4. The apparatus according to claim 1, wherein a separate adapter
device (AD) is provided for at least one pair of termination and
adaptation function means (60, 61) between non adjacent layers.
5. The apparatus according to claim 4, wherein said non adjacent
layers are selected from the group consisting of: Multi Protocol
Label Switching (MPLS) layer--SDH Higher Order (HPC) layer; Multi
Protocol Label Switching (MPLS) layer--Optical Data Unit layer
(ODU); Resilient Packet Ring layer (RPR)--SDH Higher Order (HPC)
layer; and Resilient Packet Ring layer (RPR)--Optical Data Unit
layer (ODU).
6. The apparatus according to claim 1, wherein a separate adapter
device (AD) is provided for at least one pair of termination and
adaptation function means (60, 61) between adjacent layers and
wherein a separate adapter device (AD) is provided for at least one
pair of termination and adaptation function means (60, 61) between
non adjacent layers.
7. The apparatus according to claim 1, wherein at least one of said
input/output port devices (PD) comprises packet termination
function means (Pkt proc, Traffic mng).
8. The apparatus according to claim 7, wherein it further comprises
a first backpanel driver (BKP1) for transmitting terminated packet
signals to said matrix (M) for performing packet layer
switching.
9. The apparatus according to claim 7, wherein it further comprises
a selector (SEL), said selector (SEL) receives packet signals and
outputs said received packet signals either to said packet
termination function means (Pkt proc, Traffic mng) or to a plug-in
module (AD1) which is apt to adapt (L2 so-sk) said packet signals
into time division multiplex signals and terminate said packet
signals on time division multiplex layer.
10. The apparatus according to claim 9, wherein said plug-in module
(AD1) comprises: Lower Order Path Termination means (LPT so-sk),
Higher Order Path Termination means (HPT so-sk); and Optical Data
Unit termination means (ODU so-sk).
11. The apparatus according to claim 9, wherein said first
backpanel driver (BKP1) transmits signals from said plug-in module
(AD1) to said matrix (M) for performing time division multiplex
layer switching.
12. The apparatus according to claim 7, wherein said packet
termination function means (Pkt proc, Traffic mng), said selector
(SEL) and said plug-in module (AD1) are arranged on a first board
(L2 board).
13. The apparatus according to claim 1, wherein at least one of
said input/output port devices (PD) comprises TDM termination
function means (TTF sk-so) and processing means (HVC).
14. The apparatus according to claim 13, wherein it further
comprises a second backpanel driver (BKP3) for transmitting said
terminated/processed TDM signals to said matrix (M) for performing
TDM layer switching.
15. The apparatus according to claim 13, wherein said TDM
termination function means (TTF sk-so) and said processing means
(HVC) are arranged on a second board (SDH board).
16. The apparatus according to claim 1, wherein it further
comprises a Higher Order Adaptation board (AD2) receiving Lower
Order TDM signals and outputting higher order TDM signals, said
Higher Order Adaptation board (AD2) in turn comprising an adapter
device comprising adaptation function means (HPA sk-so) and
termination function means (HPT so-sk).
17. The apparatus according to claim 1, wherein said electrical
matrix (M) has a total switching capacity which could be shared by
different layer signals.
18. The apparatus according to claim 1, wherein it further
comprises an optical switch device (MO) transparent with respect to
incoming optical signal format.
19. The apparatus according to claim 18, wherein said optical
switch device (MO) has a total optical switching capacity which
could be shared by different layer signals.
20. An integrated transport network comprising one or more
multi-service apparatuses (P) according to claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the field of
telecommunications and, in particular, to the field of network
elements. Even more in particular, the present invention relates to
a multi-service transport apparatus suitable for handling signals
coming from an integrated transport network.
[0003] 2. Description of the Prior Art
[0004] Transmission networks can be classified according to their
geographical extension, their topology and the transmission
protocol they use for transmitting information.
[0005] In particular, according to the geographical extension it is
possible to identify, for instance, two types of transmission
network: [0006] Local Area Network (LAN), where network nodes are
rather close to each other, for example inside the same building or
group of buildings; and [0007] Wide Area Network (WAN), used for
interconnecting LANs that are far from each others.
[0008] From the topological point of view, LANs have usually a bus
or ring configuration, while WANs may have nodes arranged according
to a mesh, a bus or a ring configuration.
[0009] With regard to the transmission protocol, networks may be
distinguished in circuit switched networks and packet switched
networks. In circuit switched networks, information is transported
from a source node to a destination node by a continuous stream of
digital signals propagating through the network at a constant rate;
the stream is organized in a sequence of frames with fixed length
and format. Information transmission starts only when a "circuit"
(namely, a route interconnecting the source node to the destination
node) has been established in the network. Said circuit is used to
transmit the whole stream of digital signals. SDH/Sonet synchronous
protocol and PDH asynchronous protocol are examples of circuit
switched network standards.
[0010] In contrast, in a packet switched network the information is
exchanged in bursts called "packets". Each packet includes the
address of its destination node and is individually transmitted
through the network. Each packet is routed node by node according
to the traffic conditions; at the destination node, the correct
packet sequence is reconstructed to recover the information. Packet
length may vary depending on the information type (voice, data or
video) and on network features (bit rate, network extension).
Ethernet and Resilient Packet Ring (RPR) are examples of packet
switched network standards.
[0011] Nowadays, there exist integrated transport networks, i.e.
networks comprising different LANs interconnected by backbones,
where LANs may provide different services, each service being
supported by a different network standard, either circuit switched
or packet switched. For instance, a single integrated transport
network may include LANs providing both Ethernet- and ATM-supported
services; in turn, data related to these services may be mapped,
for example, according to the SDH/Sonet standard and may be
transported along the network backbones according to that
standard.
[0012] In an integrated transport network, each standard which is
supported by the network may be represented by a different network
layer. Each layer N is interfaced with the two adjacent layers N+1
and N-1. Layer N+1 is Client of layer N, while layer N-1 is Server
of layer N. In other words, a signal according to layer N+1 can be
suitably mapped and transported in a signal structure according to
layer N. In turn, the signal structure according to layer N can be
suitably mapped and transported into a signal structure according
to layer N-1.
[0013] For example, an integrated transport network comprising SDH
and Ethernet signals can be represented by a three-layer hierarchy,
where Ethernet is layer #3, SDH-Lower Order is layer #2 and
SDH-Higher Order is layer #1. In other words, Ethernet is Client of
SDH-Lower Order, which is in turn Client of SDH-Higher Order.
[0014] The simultaneous presence of a plurality of network layers,
i.e. of a plurality of network standards supported by the same
integrated transport network, requires multi-service transport
apparatuses, suitable for handling all the signals coming from the
integrated network at each network layer. In particular, a
multi-service transport apparatus should be able to carry out all
the signal processing functions, such as termination, adaptation
and switching, according to each network layer. For instance, a
multi-service transport apparatus should be able to extract a group
of Ethernet packets from an incoming SDH-Higher Order frame, to
perform a packet-switching operation on the packets and finally
either to transmit the packets over a LAN or to map the packets
back in a SDH-Higher Order frame and to transmit the frame through
the backbone. Hence, a multi-service transport apparatus comprises
input/output ports, switch elements (such as TDM matrices or packet
matrices) and interfaces between layers. With such an equipment,
the apparatus is able to interconnect each input of each network
layer to each output of the same layer and of the other layers.
[0015] Different multi-service transport apparatuses are known in
the art. These known apparatuses are based on different approaches,
depending on the integration level of the signal processing
functions related to different layers: "multi network element"
approach; and "single network element" approach.
[0016] The "multi network element" approach consists in assembling
a plurality of single-service shelves, each shelf comprising
input/output ports and switch elements, able to manage signals
according to one single layer, and interfaces. Yet, such an
approach is disadvantageous, since the presence of one shelf for
each of the supported layers implies extra-costs, due to a non
optimised exploitation of each shelf and to the management of
different shelves, and an increase of the overall dimension of the
apparatus.
[0017] Lower costs and dimensions can be obtained by a
multi-service transport apparatus according to the "single network
element" approach, where processing functions related to different
layers are integrated into a single shelf. Three different
multi-service apparatuses are known. Each of them is based either
on a TDM matrix, a packet matrix; or a TDM matrix & a packet
matrix.
[0018] In the first case, the multi-service apparatus comprises a
main TDM matrix (for example a matrix for SDH/Sonet switching) and
a plurality of secondary packet matrices with smaller dimensions.
Yet, this approach exhibits some disadvantages, such as a reduced
scalability of the packet traffic.
[0019] In the second case, the apparatus is based on a main packet
matrix and on a plurality of input/output ports, said ports
comprising interfaces to convert all the incoming traffic into
packet-switchable signals. This approach however, even though
advantageous with respect to the previous one in terms of
scalability, is a non-layered approach, i.e. it is not consistent
with the layered structure of the transport network. This prevents
the implementation and the coexistence of some network protection
mechanisms. Moreover, the interfaces included into the input/output
ports are very complex and expensive.
[0020] In the third case the apparatus comprises two main matrices,
i.e. a TDM matrix and a packet matrix, with input/output ports
suitable to direct the incoming traffic on the matrices and means
to interface the two matrices. This approach is disadvantageous,
since it implies extra-costs due to the presence of the two
matrices and of the additional functions aimed to direct the
traffic.
SUMMARY OF THE INVENTION
[0021] The general object of the present invention is to provide a
multi-service transport apparatus for integrated transport networks
which overcomes the aforesaid problems of the prior art.
[0022] In particular, a first object of the present invention is to
provide a multi-service transport apparatus for integrated
transport networks able to carry out all the signal processing
functions, such as termination, adaptation and switching, according
to the standards for integrated transport networks, said
multi-service transport apparatus allowing interconnection between
all the layers of the integrated transport network without damaging
its layered structure, and such that all the cascaded protection
schemes provided by the different layers can be implemented.
[0023] Still a further object of the present invention is to
provide a multi-service transport apparatus for integrated
transport networks with no extra-costs due to the duplication of
the devices and with an optimised exploitation of the devices
provided inside the multi-service apparatus.
[0024] These and other objects are achieved, according to the
present invention, by a multi-service transport apparatus according
to claim 1. Further advantageous features of the present invention
are set forth into the dependent claims. All the claims are deemed
to be an integral part of the present description.
[0025] The present invention provides a multi-service apparatus for
an integrated transport network which comprises a plurality of
signal layers. The apparatus comprises an electrical matrix,
termination function means handling signals incoming at apparatus
inputs, a plurality of termination function means interfacing
different layers, and adaptation function means. The termination
function means handling incoming signals are implemented in
input/output port devices; furthermore, the termination function
means interfacing different layers and the adaptation function
means are implemented in adapter devices. The matrix performs
exclusively the switching of the incoming signals that are already
terminated and adapted by the input/output port devices and by the
adapter devices and it is transparent with respect to signal
format.
[0026] According to one embodiment, a separate adapter device is
provided for at least one pair of termination and adaptation
function means between adjacent layers. The adjacent layers could
be: Ethernet layer & Multi Protocol Label Switching layer;
Multi Protocol Label Switching layer & Resilient Packet Ring
layer; Resilient Packet Ring layer & SDH Lower Order layer; SDH
Lower Order layer & SDH Higher Order layer; and SDH Higher
Order layer & Optical Data Unit layer.
[0027] According to another embodiment, a separate adapter device
is provided for at least one pair of termination and adaptation
function means between non adjacent layers. The non adjacent layers
could be: Multi Protocol Label Switching layer & SDH Higher
Order layer; Multi Protocol Label Switching layer & Optical
Data Unit layer; Resilient Packet Ring layer & SDH Higher Order
layer; and Resilient Packet Ring layer & Optical Data Unit
layer.
[0028] According to another embodiment, a separate adapter device
is provided for at least one pair of termination and adaptation
function means between adjacent layers and wherein a separate
adapter device is provided for at least one pair of termination and
adaptation function means between non adjacent layers.
[0029] Profitably, at least one of said input/output port devices
comprises packet termination function means. Preferably, there is
also a first backpanel driver for transmitting terminated packet
signals to the matrix for performing packet layer switching.
[0030] Preferably, the apparatus further comprises a selector, said
selector receives packet signals and outputs said received packet
signals either to said packet termination function means or to a
plug-in module which is apt to adapt said packet signals into time
division multiplex signals and terminate said packet signals on
time division multiplex layer.
[0031] Typically, the plug-in module comprises: Lower Order Path
Termination means, Higher Order Path Termination means; and Optical
Data Unit termination means.
[0032] The first backpanel driver transmits signals from said
plug-in module to the matrix for performing time division multiplex
layer switching.
[0033] Profitably, said packet termination function means, said
selector and said plug-in module are arranged on a first board.
[0034] In the apparatus according to the invention, at least one of
said input/output port devices comprises TDM termination function
means and processing means. Furthermore, the apparatus comprises a
second backpanel driver for transmitting said terminated/processed
TDM signals to said matrix for performing TDM layer switching.
Profitably, said TDM termination function means and said processing
means are arranged on a second board.
[0035] The apparatus further comprises a Higher Order Adaptation
board receiving Lower Order TDM signals and outputting higher order
TDM signals, the Higher Order Adaptation board in turn comprising
an adapter device comprising adaptation function means and
termination function means.
[0036] A peculiar characteristic of the invention is that the
electrical matrix has a total switching capacity which could be
shared by different layer signals.
[0037] In a preferred embodiment, the apparatus comprises an
optical switch device transparent with respect to incoming optical
signal format. The optical switch device has a total optical
switching capacity which could be shared by different layer
signals.
[0038] Hence, in a multi-service transport apparatus according to
the present invention, the switching function, performed by a
switch device (matrix), is substantially separated from the
termination and adaptation functions. In other words, the switch
device is transparent to the format of the incoming signals, as
signals at the input of the switch device are already terminated
and adapted by the input/output port device and by the adapter
device. Accordingly, the switch device is able to switch signals
coming from different network layers; no more multiple switch
elements (TDM or packet matrices) are required to perform switching
on different layers.
[0039] The hierarchical layered structure of the network, managed
by the adapter devices, is then preserved.
[0040] Moreover, the traffic throughput corresponding to each layer
can be easily scaled by equipping a proper number of input/output
port devices and of adapter devices.
[0041] Further, according to the type of input/output port device
connected to the switch device, it is possible to share the overall
traffic throughput offered by the switch device among the different
layers, according to the traffic throughput required by each
layer.
[0042] Further features and advantages of the present invention
will become clear by the following detailed description, given by
way of example and not of limitation, to be read with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
[0043] FIG. 1 schematically shows from a logical point of view a
portion of a multi-service transport apparatus for an integrated
transport network comprising at least three layers;
[0044] FIG. 2 schematically shows a known multi-service transport
apparatus implemented according to the "multi network element"
approach;
[0045] FIG. 3 schematically shows a known multi-service transport
apparatus implemented according to the "single network element"
approach, based on a TDM matrix;
[0046] FIG. 4 schematically shows a known multi-service transport
apparatus implemented according to the "single network element"
approach, based on a packet matrix;
[0047] FIG. 5 schematically shows a known multi-service transport
apparatus implemented according to the "single network element"
approach, based on a TDM matrix and a packet matrix;
[0048] FIG. 6a schematically shows from a logical point of view a
first embodiment of a multi-service transport apparatus according
to the present invention;
[0049] FIG. 6b schematically shows from a logical point of view
another embodiment of a multi-service transport apparatus according
to the present invention; and
[0050] FIG. 7 shows the electrical scheme of a further embodiment
of a multi-service transport apparatus according to the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0051] As mentioned above, an integrated transport network deals
with different transmission standards, either circuit switched or
packet switched. All the transmission standards supported by the
network are organized into a hierarchical layered structure. A
multi-service transport apparatus for integrated transport network
thus comprises devices to handle at each network layer all the
signals incoming at the input of the apparatus.
[0052] FIG. 1 schematically shows, from a logical point of view, a
portion of a multi-service transport apparatus P for an integrated
transport network comprising at least three layers N+1, N and N-1.
Layer N+1 is Client of layer N, which is in turn Client of layer
N-1. In other words, layer N-1 is Server of layer N, which is in
turn server of layer N+1.
[0053] The apparatus P comprises, for each of the above mentioned
layers, a processing block P.sub.N+1, P.sub.N and P.sub.N-1. Each
block P.sub.N+1, P.sub.N e P.sub.N-1 comprises: [0054] an
adaptation function sink (A.sub.N+1, A.sub.N e A.sub.N-1) from the
Server layer; [0055] an adaptation function source (A'.sub.N+1,
A'.sub.N and A'.sub.N-1) to the Server layer; [0056] an input
termination function (T.sub.N+1, T.sub.N and T.sub.N-1); [0057] an
output termination function (T'.sub.N+1, T'.sub.N and T'.sub.N-1);
and [0058] a switch element (M.sub.N+1, M.sub.N and M.sub.N-1)
suitable to perform switching at each of said layers (e.g. TDM
matrix or packet matrix).
[0059] It has to be noticed that the apparatus P comprises both
termination and adaptation functions to handle signals coming at
the input of each block P.sub.N from the network, and termination
and adaptation functions suitable to interface blocks of different
layers. For clarity reasons, FIG. 1 shows only the termination and
adaptation functions suitable to interface blocks of adjacent
layers.
[0060] A signal according to layer N which is incoming at the input
of the apparatus P, is firstly received by suitable
termination/adaptation functions (not shown in FIG. 1) of the block
P.sub.N. The signal can then be switched at layer N by the switch
element M.sub.N and finally go out of the apparatus through
suitable termination/adaptation functions (not shown in FIG. 1) of
the block P.sub.N.
[0061] Alternatively, the signal according to layer N may be
received by suitable termination/adaptation functions (not shown in
FIG. 1) of the block P.sub.N, then it can be switched by the switch
element M.sub.N and finally adapted by the adaptation function
A'.sub.N which, together with the termination function T.sub.N-1,
allows the signal to pass from the Client layer N to the Server
layer N-1. Then, the signal may be switched by the switch element
M.sub.N-1 and finally go out of the apparatus P at layer N-1
through suitable termination/adaptation functions (not shown in
FIG. 1) of the block P.sub.N-1.
[0062] Alternatively, the signal according to layer N may be
received by suitable termination/adaptation functions (not shown in
FIG. 1) of the block P.sub.N, then it can be switched by the switch
element MN and finally it can pass from the Server layer N to the
Client layer N+1 through the termination function T'.sub.N and the
adaptation function A.sub.N+1. Then, the signal may be switched by
the switch element M.sub.N+1 and finally go out of the apparatus P
at layer N+1 through suitable termination/adaptation functions (not
shown in FIG. 1) of the block P.sub.N+1.
[0063] On the basis of the above considerations, it is clear that
in a multi-service apparatus of the type shown in FIG. 1 each input
of layer N is interconnected to all the output of layer N and of
layers N-1 and N+1. Moreover, in such a multi-service apparatus, it
is possible to perform switching according to each layer on all the
incoming signals according to all the three layers, thanks to the
termination and adaptation functions allowing the signal to pass
from each layer to the others.
[0064] FIG. 2 schematically shows a known multi-service transport
apparatus implemented according to the "multi network element"
approach. According to this approach, the apparatus P is obtained
by assembling a number of shelves, each shelf comprising the
processing functions according to one single layer.
[0065] In particular, the multi-service apparatus P shown in FIG. 2
comprises two shelves S.sub.1 and S.sub.2. The first shelf S.sub.1
comprise all the processing functions according to the SDH/Sonet
server layer of the network; the second shelf S.sub.2 includes all
the processing functions according to the Ethernet Client layer of
the network. S.sub.1 is then substantially an SDH/Sonet Add-Drop
Multiplexer (SDH/Sonet ADM), while S.sub.2 is substantially an
Ethernet Switch.
[0066] Hence, the multi-service apparatus P shown in FIG. 2 allows
to receive at its input either a TDM signal STM-N.sup.input from
the SDH/Sonet layer, or packet signals Eth.sup.input, FE.sup.input,
GE.sup.input, 10GE.sup.input from the Ethernet layer (respectively
in its known formats Ethernet, Fast Ethernet, Gigabit Ethernet, 10
Gigabit Ethernet). Each of these signals can be either switched at
its own layer, or pass to the other layer and then be switched.
[0067] The multi-service apparatus P shown in FIG. 2 suffers from
some disadvantages. First, a separate shelf is needed for each
network layer, independently from the traffic throughput actually
required by each layer. Referring to FIG. 2, for instance, it is
assumed that the throughput offered by the SDH/Sonet ADM is
completely used, while only a fraction of the throughput offered by
the Ethernet Switch is actually exploited. It is also assumed that
a further increase of the SDH/Sonet traffic throughput occurs. In
the apparatus P shown in FIG. 2, the increase of traffic throughput
for SDH/Sonet traffic can be achieved only by replacing the
SDH/Sonet ADM with a similar device with increased throughput, but
it is not possible to exploit the unemployed capacity offered by
the Ethernet Switch. Hence, with a "multi network element" approach
the exploitation of the devices already provided inside the
apparatus P is not optimised. In addition, having a plurality of
independent shelves results in additional costs due to the
management of each separate shelf and excessive apparatus
dimensions.
[0068] FIG. 3 schematically shows a multi-service transport
apparatus P according to a known "single network element" approach
based on a TDM matrix. The apparatus P shown in FIG. 3 comprises:
[0069] a main TDM matrix M.sub.TDM; [0070] an input and output
Optical Add-Drop Multiplexer (OADM.sup.in and OADM.sup.out
respectively) to add or drop signals according to the WDM layer;
[0071] TDM input/output ports 30 and 31 comprising
termination/adaptation functions of the signals entering the
apparatus according to the SDH/Sonet layer. The TDM input/output
ports 30 and 31 may additionally comprise functions to convert
signals coming from the WDM layer to a TDM-switchable format; and
[0072] data ports 32 which are appended to the matrix M.sub.TDM,
comprising termination/adaptation functions of signals entering the
apparatus according to the Ethernet layer and secondary packet
matrices M.sub.P to perform packet switching.
[0073] Advantageously, this approach fits the hierarchical layered
structure of the network. Nevertheless, it exhibits a reduced
scalability of the packet traffic throughput. The packet traffic
throughput, indeed, depends on the dimension of the packet matrices
M.sub.P, so it can be increased only by replacing the existing
packet matrices M.sub.P with a similar device with increased
throughput. On the contrary, increasing the number of packet
matrices M.sub.P appended to the main TDM matrix M.sub.TDM does not
increase the packet traffic throughput, since the packet matrices
work in parallel. Moreover, the packet traffic mapped in STM-N
frames must always cross the M.sub.TDM matrix, even if it has to
undergo packet switching.
[0074] Further approaches for providing multi-service transport
apparatus are known; FIGS. 4 and 5 schematically show,
respectively, a multi-service transport apparatus according to the
known single network elements approach based on a packet matrix
(FIG. 4), and on a TDM matrix & a packet matrix. (FIG. 5)
[0075] Referring to FIG. 4 the apparatus P includes a packet matrix
and means for converting all the incoming traffic in
packet-switchable signals. This way, all the switching functions
are implemented by the packet matrix.
[0076] In particular, the apparatus P includes: [0077] a main
packet matrix M.sub.P; [0078] an input and an output Optical
Add-Drop Multiplexer (OADM.sup.in and OADM.sup.out, respectively)
to add and drop signals according to the WDM layer; [0079] TDM
input/output ports 30 and 31 including termination/adaptation
functions of the signals entering the apparatus according to the
SDH/Sonet layer. The ports 30 and 31 additionally comprise
TDM/Packet Adaptation functions (TDM/P) and Packet/TDM Adaptation
functions (P/TDM) to convert the SDH/Sonet signals in packet
signals and vice-versa. In particular, the TDM/Packet Adaptation
consists in splitting the continuous stream of incoming STM-N
frames in cells, while the Packet/TDM Adaptation consists in
assembling the cells to recover the sequence of STM-N frames. The
TDM input/output ports 30 and 31 may additionally comprise
functions to convert signals coming from the WDM layer to a
TDM-switchable format; and [0080] data input/output ports 40 and 41
for termination/adaptation of signals according to the Ethernet
layer.
[0081] The main disadvantages of this approach are the cost of the
TDM/Packet Adaptation and Packet/TDM Adaptation functions and the
fact that this approach can not maintain the hierarchical layered
structure of the network. Indeed, the TDM and packet switching
functions collapse in a single switching function performed by the
packet matrix M.sub.P, i.e. the functional hierarchy of the layers
is not preserved inside the apparatus. This prevents the
implementation of the cascaded mechanism of network protection
according to the different layers. Finally, the TDM/Packet
Adaptation function may either introduce undesired delay on the
lower order traffic or lead to an under-utilization of the packet
matrix capacity.
[0082] FIG. 5 schematically shows a multi-service transport
apparatus comprising means to drive the incoming signals on one of
the two matrices. In particular, the apparatus P shown in FIG. 5
comprises: [0083] a TDM matrix M.sub.TDM and a packet matrix
M.sub.P; [0084] an input and an output Optical Add-Drop Multiplexer
(OADM.sup.in and OADM.sup.out, respectively) to add and drop
signals according to the WDM layer (.SIGMA..lamda.i.sup.input,
.SIGMA..lamda.i.sup.output); [0085] TDM input/output ports 30, 31
including termination/adaptation functions of the signals entering
the apparatus according to the SDH/Sonet layer. The TDM
input/output ports 30, 31 may additionally comprise functions to
convert signals coming from the WDM layer to a TDM-switchable
format; [0086] data input/output ports 40, 41 for
termination/adaptation of signals according to the Ethernet layer;
and [0087] a TDM-packet adapter 50 between the two matrices
M.sub.TDM and M.sub.P.
[0088] This approach disadvantageously requires the duplication of
the switch elements and extra costs due to the apparatus charged to
drive the incoming signals on one of the two matrices. The
apparatus according to this approach actually requires an
additional overhead for packet traffic over SDH/Sonet, so that this
packet traffic can be driven to the TDM-packet adapter 50 and then
to the packet matrix M.sub.P. Further additional costs are due to
the connection of each input of the apparatus P to both
matrices.
[0089] FIG. 6a shows from a logical point of view a first
embodiment of a multi-service transport apparatus for integrated
transport networks according to the present invention. The
multi-service apparatus P shown in FIG. 6a comprises a matrix M and
a plurality of termination functions 60, 60' (represented in FIG.
6a by triangles) and adaptation functions 61 (represented in FIG.
6a by trapezoids). Only a few termination and adaptation functions
60, 60', 61 have been indicated for clarity. The termination
functions can be divided into termination functions 60' handling
signals incoming at the input of the apparatus P from the network,
and termination functions 60 interfacing different layers, either
adjacent or not adjacent.
[0090] According to the present invention, the termination
functions 60' according to each network layer are implemented in
input/output port devices PD.
[0091] Moreover, according to the present invention, optional
termination functions 60 and adaptation functions 61 interfacing
different layers are implemented in adapter devices AD. In FIG. 6a,
for clarity reasons, a single adapter device AD including a
termination function 60 and an adaptation function 61 is shown;
however, a separate AD is provided for each pair of termination and
adaptation functions between different layers.
[0092] Each adapter device AD is independent and can thus be
inserted into the apparatus in case of need, i.e. when two or more
network layers must be interfaced. Each adapter device may include
termination and adaptation functions for interfacing two or more
levels, adjacent or not. For instance, the multi-service apparatus
P shown in FIG. 6a, given by way of example, comprises an adapter
device for each pair of adjacent layers, i.e. an adapter device for
interfacing: Ethernet (L2)--Multi Protocol Label Switching (MPLS);
MPLS--Resilient Packet Ring (RPR); RPR--SDH Lower Order (LPC);
LPC--SDH Higher Order (HPC); and HPC--Optical Data Unit (ODU).
[0093] Additionally, the apparatus P shown in FIG. 6a includes
adapter devices suitable to interface the MPLS--HPC layers and
MPLS--ODU layers, bypassing the RPR and the LPC layers, and adapter
devices suitable to interface RPR--HPC layers and RPR--ODU layers,
bypassing the LPC layer. Yet, other combinations of interfaced
layers are possible.
[0094] The implementation of the termination and adaptation
functions in dedicated input/output port devices PD and adapter
devices AD allows to implement the switching functions according to
all the network layers into a single electric switch device or
electric matrix M. Said matrix M performs exclusively the switching
of the incoming signals, that are already terminated and adapted by
the input/output port devices and by the adapter devices. Thus, the
matrix M is able to switch signals according to all the network
layers, both circuit switched or packet switched. In other words,
the switch function is the same for all the incoming signals, both
belonging to TDM traffic and to packet traffic. The switching
function is transparent with respect to the signal format.
[0095] In FIG. 6a, the matrix M is represented as a group of
different switch elements or matrices with different logical
function; in particular, in the scheme in FIG. 6a a separate
logical function is highlighted for each network layer: L2
switching for Ethernet layer; MPLS switching for MPLS layer; RPR
switching for RPR layer; Lower Order Path Connection (LPC) for
SDH-Lower Order; Higher Order Path Connection (HPC) for SDH-Higher
Order; and ODU switching for ODU layer.
[0096] However, this subdivision is merely logical, and not
physical. Thanks to the implementation of termination and
adaptation functions in separate devices, a physically single
matrix M is able to switch with no distinction signals according to
different layers. The logical function of each input of the matrix
M depends exclusively on the type of input/output port device
and/or adapter device connected to it. The traffic throughput of
each network layer thus depends on the number of input/output port
devices or of adapter devices equipped and connected to the matrix
M.
[0097] The multi-service apparatus P according to the present
invention may optionally comprise optical switch devices, such as
the ones employed in the Optical Multiplex Section (OMS) layer and
in the Optical Channel (Och) layer, as shown in FIG. 6b. As for the
case of electrical signal processing, also in case of optical
signal processing the termination and adaptation functions are
implemented in dedicated input/output port devices and adapter
devices, so that the two switch functions relating to the two
optical layers may be implemented in a single optical switch
device, or optical matrix MO, transparent with respect to the
format of the optical signal.
[0098] The present invention results in a number of advantages.
Firstly, the apparatus exhibits a hierarchical structure managed by
the adapter devices and consistent with the hierarchical layered
structure of an integrated transport network. It follows that an
apparatus according to the present invention is compatible with the
implementation of network protection schemes according to the
different layers.
[0099] Moreover, the implementation of termination and adaptation
functions to interface different layers in adapter cards allows to
change the throughput percentage of each single network layer of
the overall throughput offered by the matrix M, by simply changing
the number of input/output port devices and adapter devices
equipped and connected to the matrix M.
[0100] Finally, the complexity and the cost of the interface
functions between different layers is shared among physically
separated elementary adapter devices, which can be inserted one by
one into the apparatus only in case of need. This way, the cost of
the overall multi-service apparatus is actually proportional to the
actual traffic throughput provided by the multi-service
apparatus.
[0101] FIG. 7 shows the electrical scheme of a further embodiment
of a multi-service transport network according to the present
invention. The multi-service apparatus P shown in FIG. 7 comprises:
[0102] a matrix board MB comprising an electrical matrix M; [0103]
an SDH board, i.e. an input/output port device comprising
termination/adaptation functions to terminate and adapt STM-n
frames coming from the SDH/Sonet layer; and [0104] an L2 board,
i.e. an input/output port device comprising termination/adaptation
functions to terminate and adapt packets coming from the Ethernet
layer.
[0105] Optionally, the apparatus P may include adapter devices to
interface the different layers. Apparatus P of FIG. 7, for
instance, comprises two adapter devices AD1 and AD2, differently
implemented. The first adapter device AD1 consists in a
Multi-Service Plug-In Module, i.e. a device comprising a plurality
of termination and adaptation functions which, in case of need, can
be plugged-in on a input/output port device. For example, in the
apparatus of FIG. 7 the Multi-Service Plug-In Module is plugged-in
on the L2 board, and it comprises termination and adaptation
functions to interface Ethernet layer and SDH--Lower Order layer,
Ethernet layer and SDH--Higher Order layer, and Ethernet layer and
Optical Data Unit layer.
[0106] The second adapter device AD2 consists in a Higher Order
Adaptation board, i.e. in an adapter device comprising termination
and adaptation functions to interface SDH Lower Order and SDH
Higher Order layers, implemented on a dedicated board which, in
case of need, can be inserted into the apparatus P. The AD2 device
can be individually inserted into the apparatus by connecting its
input/output directly to the matrix board MB.
[0107] Hence, an Ethernet signal (e.g. E, GE or 10 GE) incoming at
the input of the apparatus P enters the L2 board through the PHY
(physical termination of electric layer 1); afterwards, said
Ethernet signal may be: [0108] processed by the packet termination
functions laying on the L2 board (Pkt proc, Traffic mng) and then,
through the backpanel driver BKP1, be transmitted to the matrix
board MB, where a portion of the matrix performs packet switching;
or [0109] processed by the adaptation and termination functions
laying on the adapter device AD1, which allow to convert the signal
to a higher network layer, where it can be switched by another
portion of the matrix M laying on the matrix board MB.
[0110] In this latter case, the Ethernet signal is directed to the
Multi-Service Plug-In Module, where it is adapted by the L2 so-sk
adaptation function. Afterwards, the Ethernet signal may be
terminated according to the SDH--Lower Order layer by the Lower
Order Path Termination function (LPT so-sk) and then be transmitted
through the backpanel driver BKP1 to the matrix board, where a
portion of the matrix M performs SDH--Lower Order switching. The
signal can be switched either to the output of the matrix board MB
connected to input/output port devices (not shown in FIG. 7), or to
an output of the matrix board MB connected to the adapter device
AD2. The adapter device AD2 can adapt the signal through the Higher
Path Adaptation function (HPA sk-so) and terminate it according to
the SDH--Higher Order layer through the Higher Order Path
Termination function (HPT so-sk). The signal can finally be
transmitted to the matrix board MB through the backpanel driver
BKP2, where another portion of the matrix M performs SDH--Higher
Order switching.
[0111] Alternatively, the Ethernet signal at the input of the L2
board can be directed to the Multi-Service Plug-In Module, where it
is adapted by the L2 so-sk function and then directly terminated
according to the SDH--Higher Order layer through the Higher Order
Path Termination function (HPT so-sk). Then, the signal can be sent
through the backpanel driver BKP1 to the matrix board MB, where a
portion of the matrix M performs SDH--Higher Order switching.
[0112] Alternatively, the Ethernet signal at the input of the L2
board can be directed to the Multi-Service Plug-In Module, where it
is adapted by the L2 so-sk function and then directly terminated
according to the Optical Data Unit layer through the Optical Data
Unit termination function (ODU so-sk). Then, the signal can be sent
through the backpanel driver BKP1 to the matrix board MB, where a
portion of the matrix performs ODU switching.
[0113] At the input of the apparatus P shown in FIG. 7 it is also
possible to have STM-N frames according to the SDH/Sonet layer.
Said STM-N frames are received by the apparatus P through the SDH
board, where they undergo termination though the Transport Terminal
Function (TTF sk-so) and processing through an HVC block. Finally,
the frames are sent via backpanel driver BKP3 to the matrix board
MB, where a further portion of the matrix M performs SDH Higher
Order switching.
[0114] It is important to notice that all the aforesaid switching
functions (packet switching, SDH--Lower Order switching,
SDH--Higher Order switching and ODU switching), performed by
different portions of the matrix M laying on the matrix board MB,
are actually the same switching function, as termination of signals
according to different layers is implemented before entering the
matrix board. Nevertheless, according to the format of the
terminated signals entering the matrix board through the backpanel
drivers of the input/output port devices and of the adapter
devices, this switching function corresponds to: [0115] an L2
switching function in case of packet-terminated signals; or [0116]
a Lower Order Path Connection switching function (LPC) in case of
SDH--Lower Order terminated signals; or [0117] a Higher Order Path
Connection switching function (HPC) in case of SDH--Higher Order
terminated signals; or finally [0118] an ODU switching function in
case of ODU terminated signals.
[0119] In other words, each portion of the matrix M laying on the
matrix board MB is able to switch every type of incoming signal,
according to the type of input/output port device or adapter device
connected to it.
* * * * *