U.S. patent application number 13/092752 was filed with the patent office on 2011-12-08 for name services for virtual cluster switching.
This patent application is currently assigned to BROCADE COMMUNICATIONS SYSTEMS, INC.. Invention is credited to Phanidhar Koganti, Suresh Vobbilisetty, Jesse B. Willeke.
Application Number | 20110299535 13/092752 |
Document ID | / |
Family ID | 45064423 |
Filed Date | 2011-12-08 |
United States Patent
Application |
20110299535 |
Kind Code |
A1 |
Vobbilisetty; Suresh ; et
al. |
December 8, 2011 |
NAME SERVICES FOR VIRTUAL CLUSTER SWITCHING
Abstract
One embodiment of the present invention provides a switch that
facilitates name services in a virtual cluster switch. The switch
includes a name service database indicating at least one media
access control (MAC) address learned at a second switch. The switch
also includes a control mechanism. During operation, the control
mechanism distributes information on a locally learned MAC address
to the second switch. In addition, the control mechanism receives
information on a MAC address learned at the second switch.
Inventors: |
Vobbilisetty; Suresh; (San
Jose, CA) ; Koganti; Phanidhar; (Sunnyvale, CA)
; Willeke; Jesse B.; (Broomfield, CO) |
Assignee: |
BROCADE COMMUNICATIONS SYSTEMS,
INC.
San Jose
CA
|
Family ID: |
45064423 |
Appl. No.: |
13/092752 |
Filed: |
April 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61352264 |
Jun 7, 2010 |
|
|
|
61380803 |
Sep 8, 2010 |
|
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Current U.S.
Class: |
370/392 ;
370/401 |
Current CPC
Class: |
H04L 67/1044 20130101;
H04L 12/4633 20130101; H04L 65/4076 20130101; H04L 49/70 20130101;
H04L 61/6022 20130101; H04L 45/00 20130101; H04L 12/4625 20130101;
H04L 41/085 20130101; H04L 49/555 20130101 |
Class at
Publication: |
370/392 ;
370/401 |
International
Class: |
H04L 12/56 20060101
H04L012/56 |
Claims
1. A switch, comprising: a name service database indicating at
least one media access control (MAC) address learned at a second
switch; and a control mechanism configured to: distribute
information on a locally learned MAC address to the second switch;
and receive information on a MAC address learned at the second
switch.
2. The switch of claim 1, wherein the switch and the second switch
are members of a virtual cluster switch comprising one or more
physical switches which are allowed to be coupled in an arbitrary
topology; and wherein the virtual cluster switch appears to be one
single switch.
3. The switch of claim 1, wherein while distributing information to
the second switch, the control mechanism is configured to construct
a Fibre Channel registered state change notification (RSCN)
encapsulated in a transparent interconnection of lots of links
(TRILL) header.
4. The switch of claim 1, wherein the distributed information to
the second switch includes the MAC address and an identifier of the
switch.
5. The switch of claim 4, wherein the distributed information
further includes: an identifier of a port to which a host
corresponding to the MAC address is coupled; and a virtual local
area network (VLAN) tag associated with the MAC address.
6. The switch of claim 1, wherein the control mechanism is further
configured to send an update to second switch when a link or port
within a multi-chassis trunk fails.
7. The switch of claim 6, wherein the update indicates that an end
host previously connected via a multi-chassis trunk is now
connected with a physical switch.
8. A switching system, comprising: a plurality of member; and a
name service database stored on a first member switch, wherein the
name service database indicates at least one MAC address learned at
a second member switch; a control mechanism residing in the first
member switch and configured to: distribute information on a MAC
address locally learned on the first member switch to the second
member switch; and receive information on a MAC address learned at
the second switch.
9. The switching system of claim 8, wherein the switch system is a
virtual cluster switch comprising one or more physical switches
which are allowed to be coupled in an arbitrary topology; and
wherein the virtual cluster switch appears to be one single
switch.
10. The switching system of claim 8, wherein while distributing
information to the second member switch, the control mechanism is
configured to construct a Fibre Channel registered state change
notification (RSCN) encapsulated in a transparent interconnection
of lots of links (TRILL) header.
11. The switching system of claim 8, wherein the distributed
information to the second switch includes the MAC address and an
identifier of the switch.
12. The switching system of claim 11, wherein distributed
information further includes: an identifier of a port to which a
host corresponding to the MAC address is coupled; and a virtual
local area network (VLAN) tag associated with the MAC address.
13. The switching system of claim 8, wherein the control mechanism
is further configured to send an update to second switch when a
link or port within a multi-chassis trunk fails.
14. The switching system of claim 13, wherein the update indicates
that an end host previously connected via a multi-chassis trunk is
now connected with a physical switch.
15. A method, comprising: maintaining at a first switch a name
service database which indicates at least MAC address learned at a
second switch; distribute information on a locally learned MAC
address to the second switch; and receive information on a MAC
address learned at the second switch.
16. The method of claim 15, wherein the first switch and the second
switch are members of a virtual cluster switch comprising one or
more physical switches which are allowed to be coupled in an
arbitrary topology; and wherein the virtual cluster switch appears
to be one single switch.
17. The method of claim 15, wherein distributing information to the
second switch comprises constructing a Fibre Channel registered
state change notification (RSCN) encapsulated in a transparent
interconnection of lots of links (TRILL) header.
18. The method of claim 15, wherein the distributed information to
the second switch includes the MAC address and an identifier of the
switch.
19. The method of claim 18, wherein distributed information further
includes: an identifier of a port to which a host corresponding to
the MAC address is coupled; and a virtual local area network (VLAN)
tag associated with the MAC address.
20. The method of claim 18, further comprising sending an update to
second switch when a link or port within a multi-chassis trunk
fails.
21. The method of claim 20, wherein the update indicates that an
end host previously connected via a multi-chassis trunk is now
connected with a physical switch.
22. A switch means, comprising: a name service database means for
indicating at least one media access control (MAC) address learned
at a second switch; and a control means for: distributing
information on a locally learned MAC address to the second switch;
and receiving information on a MAC address learned at the second
switch.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/352,264, Attorney Docket Number
BRCD-3015.0.1.US.PSP, entitled "Name Services for Virtual Cluster
Switching," by inventors Suresh Vobbilisetty, Phanidhar Koganti,
and Jesse B. Willeke, filed 7 Jun. 2010, and U.S. Provisional
Application No. 61/380,803, Attorney Docket Number
BRCD-3015.0.2.US.PSP, entitled "Name Services for Virtual Cluster
Switching," by inventors Suresh Vobbilisetty, Phanidhar Koganti,
and Jesse B. Willeke, filed 8 Sep. 2010, the disclosure of which is
incorporated by reference herein.
[0002] The present disclosure is related to U.S. patent application
Ser. No. 12/725,249, (attorney docket number BRCD-112-0439US),
entitled "REDUNDANT HOST CONNECTION IN A ROUTED NETWORK," by
inventors Somesh Gupta, Anoop Ghanwani, Phanidhar Koganti, and
Shunjia Yu, filed 16 Mar. 2010; and
[0003] U.S. patent application Ser. No. 13/087,239, (attorney
docket number BRCD-3008.1.US.NP), entitled "VIRTUAL CLUSTER
SWITCHING," by inventors Suresh Vobbilisetty and Dilip Chatwani,
filed 14 Apr. 2011;
[0004] the disclosures of which are incorporated by reference
herein.
BACKGROUND
[0005] 1. Field
[0006] The present disclosure relates to network design. More
specifically, the present disclosure relates to a method for a
constructing a scalable switching system that facilitates automatic
configuration.
[0007] 2. Related Art
[0008] The relentless growth of the Internet has brought with it an
insatiable demand for bandwidth. As a result, equipment vendors
race to build larger, faster, and more versatile switches to move
traffic. However, the size of a switch cannot grow infinitely. It
is limited by physical space, power consumption, and design
complexity, to name a few factors. More importantly, because an
overly large system often does not provide economy of scale due to
its complexity, simply increasing the size and throughput of a
switch may prove economically unviable due to the increased
per-port cost.
[0009] One way to increase the throughput of a switch system is to
use switch stacking. In switch stacking, multiple smaller-scale,
identical switches are interconnected in a special pattern to form
a larger logical switch. However, switch stacking requires careful
configuration of the ports and inter-switch links. The amount of
required manual configuration becomes prohibitively complex and
tedious when the stack reaches a certain size, which precludes
switch stacking from being a practical option in building a
large-scale switching system. Furthermore, a system based on
stacked switches often has topology limitations which restrict the
scalability of the system due to fabric bandwidth
considerations.
[0010] In addition, the evolution of virtual computing has placed
additional requirements on the network. For example, as the
locations of virtual servers become more mobile and dynamic, it is
often important for the network to update its knowledge of the
location of these virtual servers quickly.
SUMMARY
[0011] One embodiment of the present invention provides a switch
that facilitates name services in a virtual cluster switch. The
switch includes a name service database indicating at least one
media access control (MAC) address learned at a second switch. The
switch also includes a control mechanism. During operation, the
control mechanism distributes information on a locally learned MAC
address to the second switch. In addition, the control mechanism
receives information on a MAC address learned at the second
switch.
[0012] In a variation on this embodiment, the switch and the second
switch are members of a virtual cluster switch comprising one or
more physical switches which are allowed to be coupled in an
arbitrary topology. Furthermore, the virtual cluster switch appears
to be one single switch.
[0013] In a variation on this embodiment, while distributing
information to the second switch, the control mechanism constructs
a Fibre Channel registered state change notification (RSCN)
encapsulated in a transparent interconnection of lots of links
(TRILL) header.
[0014] In a variation on this embodiment, the distributed
information to the second switch includes the MAC address and an
identifier of the switch.
[0015] In a further variation, the distributed information further
includes an identifier of a port to which a host corresponding to
the MAC address is coupled and a virtual local area network (VLAN)
tag associated with the MAC address.
[0016] In a variation on this embodiment, the control mechanism
further sends an update to second switch when a link or port within
a multi-chassis trunk fails.
[0017] In a further variation, the update indicates that an end
host previously connected via a multi-chassis trunk is now
connected with a physical switch.
BRIEF DESCRIPTION OF THE FIGURES
[0018] FIG. 1A illustrates an exemplary virtual cluster switch
(VCS) system, in accordance with an embodiment of the present
invention.
[0019] FIG. 1B illustrates an exemplary VCS system where the member
switches are configured in a CLOS network, in accordance with an
embodiment of the present invention.
[0020] FIG. 2 illustrates the protocol stack within a virtual
cluster switch, in accordance with an embodiment of the present
invention.
[0021] FIG. 3 illustrates an exemplary configuration of a virtual
cluster switch, in accordance with an embodiment of the present
invention.
[0022] FIG. 4 illustrates an exemplary configuration of how a
virtual cluster switch can be connected to different edge networks,
in accordance with an embodiment of the present invention.
[0023] FIG. 5A illustrates how a logical Fibre Channel switch
fabric is formed in a virtual cluster switch in conjunction with
the example in FIG. 4, in accordance with an embodiment of the
present invention.
[0024] FIG. 5B illustrates an example of how a logical FC switch
can be created within a physical Ethernet switch, in accordance
with one embodiment of the present invention.
[0025] FIG. 6 illustrates an exemplary VCS configuration database,
in accordance with an embodiment of the present invention.
[0026] FIG. 7 illustrates an exemplary process of a switch joining
a virtual cluster switch, in accordance with an embodiment of the
present invention.
[0027] FIG. 8 presents a flowchart illustrating the process of
looking up an ingress frame's destination MAC address and
forwarding the frame in a VCS, in accordance with one embodiment of
the present invention.
[0028] FIG. 9 illustrates how data frames and control frames are
transported through a VCS, in accordance with one embodiment of the
present invention.
[0029] FIG. 10 illustrates an example of name service operation in
a VCS, in accordance with one embodiment of the present
invention.
[0030] FIG. 11 presents a flowchart illustrating the process of
distributing learned MAC information by the Ethernet name service
in a VCS, in accordance with one embodiment of the present
invention.
[0031] FIG. 12 presents a flowchart illustrating the process of
distributing information of a learned MAC address via an MCT, in
accordance with one embodiment of the present invention.
[0032] FIG. 13 presents a flowchart illustrating the process of
updating the link state in an MCT group, in accordance with one
embodiment of the present invention.
[0033] FIG. 14 illustrates an exemplary switch that facilitates
formation of a virtual cluster switch with Ethernet and MCT name
services, in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION
[0034] The following description is presented to enable any person
skilled in the art to make and use the invention, and is provided
in the context of a particular application and its requirements.
Various modifications to the disclosed embodiments will be readily
apparent to those skilled in the art, and the general principles
defined herein may be applied to other embodiments and applications
without departing from the spirit and scope of the present
invention. Thus, the present invention is not limited to the
embodiments shown, but is to be accorded the widest scope
consistent with the claims.
Overview
[0035] In embodiments of the present invention, the problem of
facilitating fast distribution of the location information of each
end host is solved by providing a distributed name service
throughout a virtual cluster switch. The virtual cluster switch
allows a number of switches to be inter-connected to form a single,
scalable logical switch without requiring burdensome manual
configuration. As a result, one can form a large-scale logical
switch (referred to as a "virtual cluster switch" or VCS herein)
using a number of smaller physical switches. The automatic
configuration capability provided by the control plane running on
each physical switch allows any number of switches to be connected
in an arbitrary topology without requiring tedious manual
configuration of the ports and links. This feature makes it
possible to use many smaller, inexpensive switches to construct a
large cluster switch, which can be viewed as a single logical
switch externally.
[0036] In a VCS, each member switch performs source media access
control (MAC) address learning. Once a new MAC address is observed
and learned from a port, the corresponding MAC address and
switch/port identifier information is distributed throughout the
VCS. In this way, each VCS member switch can maintain a complete
set of knowledge of the location of all the end-hosts (including
virtual machines). This knowledge allows a frame destined to any
MAC address to be properly routed to the correct switch, even if
the MAC address is not directly learned by the local switch. (Note
that, in a conventional Ethernet switch, an frame with an unknown
destination MAC address is flooded too all the ports.) In this
disclosure, the description in conjunction with FIGS. 1-9 is
associated with the general architecture of VCS, and the
description in conjunction with FIG. 10 and onward provide more
details on the advanced link tracking mechanism.
[0037] It should be noted that a virtual cluster switch is not the
same as conventional switch stacking. In switch stacking, multiple
switches are interconnected at a common location (often within the
same rack), based on a particular topology, and manually configured
in a particular way. These stacked switches typically share a
common address, e.g., IP address, so they can be addressed as a
single switch externally. Furthermore, switch stacking requires a
significant amount of manual configuration of the ports and
inter-switch links. The need for manual configuration prohibits
switch stacking from being a viable option in building a
large-scale switching system. The topology restriction imposed by
switch stacking also limits the number of switches that can be
stacked. This is because it is very difficult, if not impossible,
to design a stack topology that allows the overall switch bandwidth
to scale adequately with the number of switch units.
[0038] In contrast, a VCS can include an arbitrary number of
switches with individual addresses, can be based on an arbitrary
topology, and does not require extensive manual configuration. The
switches can reside in the same location, or be distributed over
different locations. These features overcome the inherent
limitations of switch stacking and make it possible to build a
large "switch farm" which can be treated as a single, logical
switch. Due to the automatic configuration capabilities of the VCS,
an individual physical switch can dynamically join or leave the VCS
without disrupting services to the rest of the network.
[0039] Furthermore, the automatic and dynamic configurability of
VCS allows a network operator to build its switching system in a
distributed and "pay-as-you-grow" fashion without sacrificing
scalability. The VCS's ability to respond to changing network
conditions makes it an ideal solution in a virtual computing
environment, where network loads often change with time.
[0040] Although this disclosure is presented using examples based
on the Transparent Interconnection of Lots of Links (TRILL) as the
transport protocol and the Fibre Channel (FC) fabric protocol as
the control-plane protocol, embodiments of the present invention
are not limited to TRILL networks, or networks defined in a
particular Open System Interconnection Reference Model (OSI
reference model) layer. For example, a VCS can also be implemented
with switches running multi-protocol label switching (MPLS)
protocols for the transport. In addition, the terms "RBridge" and
"switch" are used interchangeably in this disclosure. The use of
the term "RBridge" does not limit embodiments of the present
invention to TRILL networks only. The TRILL protocol is described
in IETF draft "RBridges: Base Protocol Specification," available at
http://tools.ietf.org/html/draft-ietf-trill-rbridge-protocol, which
is incorporated by reference herein
[0041] The terms "virtual cluster switch," "virtual cluster
switching," and "VCS" refer to a group of interconnected physical
switches operating as a single logical switch. The control plane
for these physical switches provides the ability to automatically
configure a given physical switch, so that when it joins the VCS,
little or no manual configuration is required.
[0042] The term "RBridge" refers to routing bridges, which are
bridges implementing the TRILL protocol as described in IETF draft
"RBridges: Base Protocol Specification." Embodiments of the present
invention are not limited to the application among RBridges. Other
types of switches, routers, and forwarders can also be used.
[0043] The terms "frame" or "packet" refer to a group of bits that
can be transported together across a network. "Frame" should not be
interpreted as limiting embodiments of the present invention to
layer-2 networks. "Packet" should not be interpreted as limiting
embodiments of the present invention to layer-3 networks. "Frame"
or "packet" can be replaced by other terminologies referring to a
group of bits, such as "cell" or "datagram."
VCS Architecture
[0044] FIG. 1A illustrates an exemplary virtual cluster switch
system, in accordance with an embodiment of the present invention.
In this example, a VCS 100 includes physical switches 101, 102,
103, 104, 105, 106, and 107. A given physical switch runs an
Ethernet-based transport protocol on its ports (e.g., TRILL on its
inter-switch ports, and Ethernet transport on its external ports),
while its control plane runs an FC switch fabric protocol stack.
The TRILL protocol facilitates transport of Ethernet frames within
and across VCS 100 in a routed fashion (since TRILL provides
routing functions to Ethernet frames). The FC switch fabric
protocol stack facilitates the automatic configuration of
individual physical switches, in a way similar to how a
conventional FC switch fabric is formed and automatically
configured. In one embodiment, VCS 100 can appear externally as an
ultra-high-capacity Ethernet switch. More details on FC network
architecture, protocols, naming/address conventions, and various
standards are available in the documentation available from the
NCITS/ANSI T11 committee (www.t11.org) and publicly available
literature, such as "Designing Storage Area Networks," by Tom
Clark, 2nd Ed., Addison Wesley, 2003, the disclosures of which are
incorporated by reference in their entirety herein.
[0045] A physical switch may dedicate a number of ports for
external use (i.e., to be coupled to end hosts or other switches
external to the VCS) and other ports for inter-switch connection.
Viewed externally, VCS 100 appears to be one switch to a device
from the outside, and any port from any of the physical switches is
considered one port on the VCS. For example, port groups 110 and
112 are both VCS external ports and can be treated equally as if
they were ports on a common physical switch, although switches 105
and 107 may reside in two different locations.
[0046] The physical switches can reside at a common location, such
as a data center or central office, or be distributed in different
locations. Hence, it is possible to construct a large-scale
centralized switching system using many smaller, inexpensive
switches housed in one or more chassis at the same location. It is
also possible to have the physical switches placed at different
locations, thus creating a logical switch that can be accessed from
multiple locations. The topology used to interconnect the physical
switches can also be versatile. VCS 100 is based on a mesh
topology. In further embodiments, a VCS can be based on a ring, fat
tree, or other types of topologies.
[0047] In one embodiment, the protocol architecture of a VCS is
based on elements from the standard IEEE 802.1Q Ethernet bridge,
which is emulated over a transport based on the Fibre Channel
Framing and Signaling-2 (FC-FS-2) standard. The resulting switch is
capable of transparently switching frames from an ingress Ethernet
port from one of the edge switches to an egress Ethernet port on a
different edge switch through the VCS.
[0048] Because of its automatic configuration capability, a VCS can
be dynamically expanded as the network demand increases. In
addition, one can build a large-scale switch using many smaller
physical switches without the burden of manual configuration. For
example, it is possible to build a high-throughput fully
non-blocking switch using a number of smaller switches. This
ability to use small switches to build a large non-blocking switch
significantly reduces the cost associated switch complexity. FIG.
1B presents an exemplary VCS with its member switches connected in
a CLOS network, in accordance with one embodiment of the present
invention. In this example, a VCS 120 forms a fully non-blocking
8.times.8 switch, using eight 4.times.4 switches and four 2.times.2
switches connected in a three-stage CLOS network. A large-scale
switch with a higher port count can be built in a similar way.
[0049] FIG. 2 illustrates the protocol stack within a virtual
cluster switch, in accordance with an embodiment of the present
invention. In this example, two physical switches 202 and 204 are
illustrated within a VCS 200. Switch 202 includes an ingress
Ethernet port 206 and an inter-switch port 208. Switch 204 includes
an egress Ethernet port 212 and an inter-switch port 210. Ingress
Ethernet port 206 receives Ethernet frames from an external device.
The Ethernet header is processed by a media access control (MAC)
layer protocol. On top of the MAC layer is a MAC client layer,
which hands off the information extracted from the frame's Ethernet
header to a forwarding database (FDB) 214. Typically, in a
conventional IEEE 802.1Q Ethernet switch, FDB 214 is maintained
locally in a switch, which would perform a lookup based on the
destination MAC address and the VLAN indicated in the Ethernet
frame. The lookup result would provide the corresponding output
port. However, since VCS 200 is not one single physical switch, FDB
214 would return the egress switch's identifier (i.e., switch 204's
identifier). In one embodiment, FDB 214 is a data structure
replicated and distributed among all the physical switches. That
is, every physical switch maintains its own copy of FDB 214. When a
given physical switch learns the source MAC address and VLAN of an
Ethernet frame (similar to what a conventional IEEE 802.1Q Ethernet
switch does) as being reachable via the ingress port, the learned
MAC and VLAN information, together with the ingress Ethernet port
and switch information, is propagated to all the physical switches
so every physical switch's copy of FDB 214 can remain synchronized.
This prevents forwarding based on stale or incorrect information
when there are changes to the connectivity of end stations or edge
networks to the VCS.
[0050] The forwarding of the Ethernet frame between ingress switch
202 and egress switch 204 is performed via inter-switch ports 208
and 210. The frame transported between the two inter-switch ports
is encapsulated in an outer MAC header and a TRILL header, in
accordance with the TRILL standard. The protocol stack associated
with a given inter-switch port includes the following (from bottom
up): MAC layer, TRILL layer, FC-FS-2 layer, FC E-Port layer, and FC
link services (FC-LS) layer. The FC-LS layer is responsible for
maintaining the connectivity information of a physical switch's
neighbor, and populating an FC routing information base (RIB) 222.
This operation is similar to what is done in an FC switch fabric.
The FC-LS protocol is also responsible for handling joining and
departure of a physical switch in VCS 200. The operation of the
FC-LS layer is specified in the FC-LS standard, which is available
at http://www.t11.org/ftp/t11/member/fc/ls/06-393v5.pdf, the
disclosure of which is incorporated herein in its entirety.
[0051] During operation, when FDB 214 returns the egress switch 204
corresponding to the destination MAC address of the ingress
Ethernet frame, the destination egress switch's identifier is
passed to a path selector 218. Path selector 218 performs a fabric
shortest-path first (FSPF)-based route lookup in conjunction with
RIB 222, and identifies the next-hop switch within VCS 200. In
other words, the routing is performed by the FC portion of the
protocol stack, similar to what is done in an FC switch fabric.
[0052] Also included in each physical switch are an address manager
216 and a fabric controller 220. Address manager 216 is responsible
for configuring the address of a physical switch when the switch
first joins the VCS. For example, when switch 202 first joins VCS
200, address manager 216 can negotiate a new FC switch domain ID,
which is subsequently used to identify the switch within VCS 200.
Fabric controller 220 is responsible for managing and configuring
the logical FC switch fabric formed on the control plane of VCS
200.
[0053] One way to understand the protocol architecture of VCS is to
view the VCS as an FC switch fabric with an Ethernet/TRILL
transport. Each physical switch, from an external point of view,
appears to be a TRILL RBridge. However, the switch's control plane
implements the FC switch fabric software. In other words,
embodiments of the present invention facilitate the construction of
an "Ethernet switch fabric" running on FC control software. This
unique combination provides the VCS with automatic configuration
capability and allows it to provide the ubiquitous Ethernet
services in a very scalable fashion.
[0054] FIG. 3 illustrates an exemplary configuration of a virtual
cluster switch, in accordance with an embodiment of the present
invention. In this example, a VCS 300 includes four physical
switches 302, 304, 306, and 308. VCS 300 constitutes an access
layer which is coupled to two aggregation switches 310 and 312.
Note that the physical switches within VCS 300 are connected in a
ring topology. Aggregation switch 310 or 312 can connect to any of
the physical switches within VCS 300. For example, aggregation
switch 310 is coupled to physical switches 302 and 308. These two
links are viewed as a trunked link to VCS 300, since the
corresponding ports on switches 302 and 308 are considered to be
from the same logical switch, VCS 300. Note that, without VCS, such
topology would not have been possible, because the FDB needs to
remain synchronized, which is facilitated by the VCS.
[0055] FIG. 4 illustrates an exemplary configuration of how a
virtual cluster switch can be connected to different edge networks,
in accordance with an embodiment of the present invention. In this
example, a VCS 400 includes a number of TRILL RBridges 402, 404,
406, 408, and 410, which are controlled by the FC switch-fabric
control plane. Also included in VCS 400 are RBridges 412, 414, and
416. Each RBridge has a number of edge ports which can be connected
to external edge networks.
[0056] For example, RBridge 412 is coupled with hosts 420 and 422
via 10GE ports. RBridge 414 is coupled to a host 426 via a 10GE
port. These RBridges have TRILL-based inter-switch ports for
connection with other TRILL RBridges in VCS 400. Similarly, RBridge
416 is coupled to host 428 and an external Ethernet switch 430,
which is coupled to an external network that includes a host 424.
In addition, network equipment can also be coupled directly to any
of the physical switches in VCS 400. As illustrated here, TRILL
RBridge 408 is coupled to a data storage 417, and TRILL RBridge 410
is coupled to a data storage 418.
[0057] Although the physical switches within VCS 400 are labeled as
"TRILL RBridges," they are different from the conventional TRILL
RBridge in the sense that they are controlled by the FC switch
fabric control plane. In other words, the assignment of switch
addresses, link discovery and maintenance, topology convergence,
routing, and forwarding can be handled by the corresponding FC
protocols. Particularly, each TRILL RBridge's switch ID or nickname
is mapped from the corresponding FC switch domain ID, which can be
automatically assigned when a switch joins VCS 400 (which is
logically similar to an FC switch fabric).
[0058] Note that TRILL is only used as a transport between the
switches within VCS 400. This is because TRILL can readily
accommodate native Ethernet frames. Also, the TRILL standards
provide a ready-to-use forwarding mechanism that can be used in any
routed network with arbitrary topology (although the actual routing
in VCS is done by the FC switch fabric protocols). Embodiments of
the present invention should be not limited to using only TRILL as
the transport. Other protocols (such as multi-protocol label
switching (MPLS) or Internet Protocol (IP)), either public or
proprietary, can also be used for the transport.
VCS Formation
[0059] In one embodiment, a VCS is created by instantiating a
logical FC switch in the control plane of each switch. After the
logical FC switch is created, a virtual generic port (denoted as
G_Port) is created for each Ethernet port on the RBridge. A G_Port
assumes the normal G_Port behavior from the FC switch perspective.
However, in this case, since the physical links are based on
Ethernet, the specific transition from a G_Port to either an FC
F_Port or E_Port is determined by the underlying link and physical
layer protocols. For example, if the physical Ethernet port is
connected to an external device which lacks VCS capabilities, the
corresponding G_Port will be turned into an F_Port. On the other
hand, if the physical Ethernet port is connected to a switch with
VCS capabilities and it is confirmed that the switch on the other
side is part of a VCS, then the G_Port will be turned into an
E_port.
[0060] FIG. 5A illustrates how a logical Fibre Channel switch
fabric is formed in a virtual cluster switch in conjunction with
the example in FIG. 4, in accordance with an embodiment of the
present invention. RBridge 412 contains a virtual, logical FC
switch 502. Corresponding to the physical Ethernet ports coupled to
hosts 420 and 422, logical FC switch 502 has two logical F_Ports,
which are logically coupled to hosts 420 and 422. In addition, two
logical N_Ports, 506 and 504, are created for hosts 420 and 422,
respectively. On the VCS side, logical FC switch 502 has three
logical E_Ports, which are to be coupled with other logical FC
switches in the logical FC switch fabric in the VCS.
[0061] Similarly, RBridge 416 contains a virtual, logical FC switch
512. Corresponding to the physical Ethernet ports coupled to host
428 and external switch 430, logical FC switch 512 has a logical
F_Port coupled to host 428, and a logical FL_Port coupled to switch
430. In addition, a logical N_Port 510 is created for host 428, and
a logical NL_Port 508 is created for switch 430. Note that the
logical FL_Port is created because that port is coupled to a switch
(switch 430), instead of a regular host, and therefore logical FC
switch 512 assumes an arbitrated loop topology leading to switch
430. Logical NL_Port 508 is created based on the same reasoning to
represent a corresponding NL_Port on switch 430. On the VCS side,
logical FC switch 512 has two logical E_Ports, which to be coupled
with other logical FC switches in the logical FC switch fabric in
the VCS.
[0062] FIG. 5B illustrates an example of how a logical FC switch
can be created within a physical Ethernet switch, in accordance
with one embodiment of the present invention. The term "fabric
port" refers to a port used to couple multiple switches in a VCS.
The clustering protocols control the forwarding between fabric
ports. The term "edge port" refers to a port that is not currently
coupled to another switch unit in the VCS. Standard IEEE 802.1Q and
layer-3 protocols control forwarding on edge ports.
[0063] In the example illustrated in FIG. 5B, a logical FC switch
521 is created within a physical switch (RBridge) 520. Logical FC
switch 521 participates in the FC switch fabric protocol via
logical inter-switch links (ISLs) to other switch units and has an
FC switch domain ID assigned to it just as a physical FC switch
does. In other words, the domain allocation, principal switch
selection, and conflict resolution work just as they would on a
physical FC ISL.
[0064] The physical edge ports 522 and 524 are mapped to logical
F_Ports 532 and 534, respectively. In addition, physical fabric
ports 526 and 528 are mapped to logical E_Ports 536 and 538,
respectively. Initially, when logical FC switch 521 is created (for
example, during the boot-up sequence), logical FC switch 521 only
has four G_Ports which correspond to the four physical ports. These
G_Ports are subsequently mapped to F_Ports or E_Ports, depending on
the devices coupled to the physical ports.
[0065] Neighbor discovery is the first step in VCS formation
between two VCS-capable switches. It is assumed that the
verification of VCS capability can be carried out by a handshake
process between two neighbor switches when the link is first
brought up.
[0066] In general, a VCS presents itself as one unified switch
composed of multiple member switches. Hence, the creation and
configuration of VCS is of critical importance. The VCS
configuration is based on a distributed database, which is
replicated and distributed over all switches.
[0067] In one embodiment, a VCS configuration database includes a
global configuration table (GT) of the VCS and a list of switch
description tables (STs), each of which describes a VCS member
switch. In its simplest form, a member switch can have a VCS
configuration database that includes a global table and one switch
description table, e.g., [<GT><ST>]. A VCS with
multiple switches will have a configuration database that has a
single global table and multiple switch description tables, e.g.,
[<GT><ST0><ST1> . . . <STn-1>]. The number
n corresponds to the number of member switches in the VCS. In one
embodiment, the GT can include at least the following information:
the VCS ID, number of nodes in the VCS, a list of VLANs supported
by the VCS, a list of all the switches (e.g., list of FC switch
domain IDs for all active switches) in the VCS, and the FC switch
domain ID of the principal switch (as in a logical FC switch
fabric). A switch description table can include at least the
following information: the IN_VCS flag, indication whether the
switch is a principal switch in the logical FC switch fabric, the
FC switch domain ID for the switch, the FC world-wide name (WWN)
for the corresponding logical FC switch; the mapped ID of the
switch, and optionally the IP address of the switch.
[0068] In addition, each switch's global configuration database is
associated with a transaction ID. The transaction ID specifies the
latest transaction (e.g., update or change) incurred to the global
configuration database. The transaction IDs of the global
configuration databases in two switches can be compared to
determine which database has the most current information (i.e.,
the database with the more current transaction ID is more
up-to-date). In one embodiment, the transaction ID is the switch's
serial number plus a sequential transaction number. This
configuration can unambiguously resolve which switch has the latest
configuration.
[0069] As illustrated in FIG. 6, a VCS member switch typically
maintains two configuration tables that describe its instance: a
VCS configuration database 600, and a default switch configuration
table 604. VCS configuration database 600 describes the VCS
configuration when the switch is part of a VCS. Default switch
configuration table 604 describes the switch's default
configuration. VCS configuration database 600 includes a GT 602,
which includes a VCS identifier (denoted as VCS_ID) and a VLAN list
within the VCS. Also included in VCS configuration database 600 are
a number of STs, such as ST0, ST1, and STn. Each ST includes the
corresponding member switch's MAC address and FC switch domain ID,
as well as the switch's interface details. Note that each switch
also has a VCS-mapped ID which is a switch index within the
VCS.
[0070] In one embodiment, each switch also has a VCS-mapped ID
(denoted as "mappedID"), which is a switch index within the VCS.
This mapped ID is unique and persistent within the VCS. That is,
when a switch joins the VCS for the first time, the VCS assigns a
mapped ID to the switch. This mapped ID persists with the switch,
even if the switch leaves the VCS. When the switch joins the VCS
again at a later time, the same mapped ID is used by the VCS to
retrieve previous configuration information for the switch. This
feature can reduce the amount of configuration overhead in VCS.
Also, the persistent mapped ID allows the VCS to "recognize" a
previously configured member switch when it re-joins the VCS, since
a dynamically assigned FC fabric domain ID would change each time
the member switch joins and is configured by the VCS.
[0071] Default switch configuration table 604 has an entry for the
mappedID that points to the corresponding ST in VCS configuration
database 600. Note that only VCS configuration database 600 is
replicated and distributed to all switches in the VCS. Default
switch configuration table 604 is local to a particular member
switch.
[0072] The "IN_VCS" value in default switch configuration table 604
indicates whether the member switch is part of a VCS. A switch is
considered to be "in a VCS" when it is assigned one of the FC
switch domains by the FC switch fabric with two or more switch
domains. If a switch is part of an FC switch fabric that has only
one switch domain, i.e., its own switch domain, then the switch is
considered to be "not in a VCS."
[0073] When a switch is first connected to a VCS, the logical FC
switch fabric formation process allocates a new switch domain ID to
the joining switch. In one embodiment, only the switches directly
connected to the new switch participate in the VCS join
operation.
[0074] Note that in the case where the global configuration
database of a joining switch is current and in sync with the global
configuration database of the VCS based on a comparison of the
transaction IDs of the two databases (e.g., when a member switch is
temporarily disconnected from the VCS and re-connected shortly
afterward), a trivial merge is performed. That is, the joining
switch can be connected to the VCS, and no change or update to the
global VCS configuration database is required.
[0075] FIG. 7 illustrates an exemplary process of a switch joining
a virtual cluster switch, in accordance with an embodiment of the
present invention. In this example, it is assumed that a switch 702
is within an existing VCS, and a switch 704 is joining the VCS.
During operation, both switches 702 and 704 trigger an FC State
Change Notification (SCN) process. Subsequently, both switches 702
and 704 perform a PRE-INVITE operation. The pre-invite operation
involves the following process.
[0076] When a switch joins the VCS via a link, both neighbors on
each end of the link present to the other switch a VCS four-tuple
of <Prior VCS_ID, SWITCH_MAC, mappedID, IN_VCS> from a prior
incarnation, if any. Otherwise, the switch presents to the
counterpart a default tuple. If the VCS_ID value was not set from a
prior join operation, a VCS_ID value of -1 is used. In addition, if
a switch's IN_VCS flag is set to 0, it sends out its interface
configuration to the neighboring switch. In the example in FIG. 7,
both switches 702 and 704 send the above information to the other
switch.
[0077] After the above PRE-INVITE operation, a driver switch for
the join process is selected. By default, if a switch's IN_VCS
value is 1 and the other switch's IN_VCS value is 0, the switch
with IN_VCS=1 is selected as the driver switch. If both switches
have their IN_VCS values as 1, then nothing happens, i.e., the
PRE-INVITE operation would not lead to an INVITE operation. If both
switches have their IN_VCS values as 0, then one of the switches is
elected to be the driving switch (for example, the switch with a
lower FC switch domain ID value). The driving switch's IN_VCS value
is then set to 1 and drives the join process.
[0078] After switch 702 is selected as the driver switch, switch
702 then attempts to reserve a slot in the VCS configuration
database corresponding to the mappedID value in switch 704's
PRE-INVITE information. Next, switch 702 searches the VCS
configuration database for switch 704's MAC address in any mappedID
slot. If such a slot is found, switch 702 copies all information
from the identified slot into the reserved slot. Otherwise, switch
702 copies the information received during the PRE-INVITE from
switch 704 into the VCS configuration database. The updated VCS
configuration database is then propagated to all the switches in
the VCS as a prepare operation in the database (note that the
update is not committed to the database yet).
[0079] Subsequently, the prepare operation may or may not result in
configuration conflicts, which may be flagged as warnings or fatal
errors. Such conflicts can include inconsistencies between the
joining switch's local configuration or policy setting and the VCS
configuration. For example, a conflict arises when the joining
switch is manually configured to allow packets with a particular
VLAN value to pass through, whereas the VCS does not allow this
VLAN value to enter the switch fabric from this particular RBridge
(for example, when this VLAN value is reserved for other purposes).
In one embodiment, the prepare operation is handled locally and/or
remotely in concert with other VCS member switches. If there is an
un-resolvable conflict, switch 702 sends out a PRE-INVITE-FAILED
message to switch 704. Otherwise, switch 702 generates an INVITE
message with the VCS's merged view of the switch (i.e., the updated
VCS configuration database).
[0080] Upon receiving the INVITE message, switch 704 either accepts
or rejects the INVITE. The INVITE can be rejected if the
configuration in the INVITE is in conflict with what switch 704 can
accept. If the INVITE is acceptable, switch 704 sends back an
INVITE-ACCEPT message in response. The INVITE-ACCEPT message then
triggers a final database commit throughout all member switches in
the VCS. In other words, the updated VCS configuration database is
updated, replicated, and distributed to all the switches in the
VCS.
Layer-2 Services in VCS
[0081] In one embodiment, each VCS switch unit performs source MAC
address learning, similar to what an Ethernet bridge does. Each
{MAC address, VLAN} tuple learned on a physical port on a VCS
switch unit is registered into the local Fibre Channel Name Server
(FC-NS) via a logical Nx_Port interface corresponding to that
physical port. This registration binds the address learned to the
specific interface identified by the Nx_Port. Each FC-NS instance
on each VCS switch unit coordinates and distributes all locally
learned {MAC address, VLAN} tuples with every other FC-NS instance
in the fabric. This feature allows the dissemination of locally
learned {MAC addresses, VLAN} information to every switch in the
VCS. In one embodiment, the learned MAC addresses are aged locally
by individual switches.
[0082] FIG. 8 presents a flowchart illustrating the process of
looking up an ingress frame's destination MAC address and
forwarding the frame in a VCS, in accordance with one embodiment of
the present invention. During operation, a VCS switch receives an
Ethernet frame at one of its Ethernet ports (operation 802). The
switch then extracts the frame's destination MAC address and
queries the local FC Name Server (operation 804). Next, the switch
determines whether the FC-NS returns an N_Port or an NL_Port
identifier that corresponds to an egress Ethernet port (operation
806).
[0083] If the FC-NS returns a valid result, the switch forwards the
frame to the identified N_Port or NL_Port (operation 808).
Otherwise, the switch floods the frame on the TRILL multicast tree
as well as on all the N_Ports and NL_Ports that participate in that
VLAN (operation 810). This flood/broadcast operation is similar to
the broadcast process in a conventional TRILL RBridge, wherein all
the physical switches in the VCS will receive and process this
frame, and learn the source address corresponding to the ingress
RBridge. In addition, each receiving switch floods the frame to its
local ports that participate in the frame's VLAN (operation 812).
Note that the above operations are based on the presumption that
there is a one-to-one mapping between a switch's TRILL identifier
(or nickname) and its FC switch domain ID. There is also a
one-to-one mapping between a physical Ethernet port on a switch and
the corresponding logical FC port.
End-to-End Frame Delivery and Exemplary VCS Member Switch
[0084] FIG. 9 illustrates how data frames and control frames are
transported in a VCS, in accordance with an embodiment of the
present invention. In this example, a VCS 930 includes member
switches 934, 936, 938, 944, 946, and 948. An end host 932 is
communicating with an end host 940. Switch 934 is the ingress VCS
member switch corresponding to host 932, and switch 938 is the
egress VCS member switch corresponding to host 938. During
operation, host 932 sends an Ethernet frame 933 to host 940.
Ethernet frame 933 is first encountered by ingress switch 934. Upon
receiving frame 933, switch 934 first extracts frame 933's
destination MAC address. Switch 934 then performs a MAC address
lookup using the Ethernet name service, which provides the egress
switch identifier (i.e., the RBridge identifier of egress switch
938). Based on the egress switch identifier, the logical FC switch
in switch 934 performs a routing table lookup to determine the
next-hop switch, which is switch 936, and the corresponding output
port for forwarding frame 933. The egress switch identifier is then
used to generate a TRILL header (which specifies the destination
switch's RBridge identifier), and the next-hop switch information
is used to generate an outer Ethernet header. Subsequently, switch
934 encapsulates frame 933 with the proper TRILL header and outer
Ethernet header, and sends the encapsulated frame 935 to switch
936. Based on the destination RBridge identifier in the TRILL
header of frame 935, switch 936 performs a routing table lookup and
determines the next hop. Based on the next-hop information, switch
936 updates frame 935's outer Ethernet header and forwards frame
935 to egress switch 938.
[0085] Upon receiving frame 935, switch 938 determines that it is
the destination RBridge based on frame 935's TRILL header.
Correspondingly, switch 938 strips frame 935 of its outer Ethernet
header and TRILL header, and inspects the destination MAC address
of its inner Ethernet header. Switch 938 then performs a MAC
address lookup and determines the correct output port leading to
host 940. Subsequently, the original Ethernet frame 933 is
transmitted to host 940.
[0086] As described above, the logical FC switches within the
physical VCS member switches may send control frames to one another
(for example, to update the VCS global configuration database or to
notify other switches of the learned MAC addresses). In one
embodiment, such control frames can be FC control frames
encapsulated in a TRILL header and an outer Ethernet header. For
example, if the logical FC switch in switch 944 is in communication
with the logical FC switch in switch 938, switch 944 can sends a
TRILL-encapsulated FC control frame 942 to switch 946. Switch 946
can forward frame 942 just like a regular data frame, since switch
946 is not concerned with the payload in frame 942.
VCS Name Services
[0087] VCS allows an interconnected fabric of RBridges to function
as a single logical switch. The VCS name services facilitate fast
distribution of run-time network state changes, including newly
learned MAC addresses (which is referred to as "Ethernet name
service" or "Ethernet NS" in this disclosure) and multi-chassis
trunk (MCT) port state updates (which is referred to as "MCT name
service" or "MCT NS" in this disclosure). More details on MCT are
provided in U.S. patent application Ser. No. 12/725,249, (attorney
docket number BRCD-112-0439US), entitled "REDUNDANT HOST CONNECTION
IN A ROUTED NETWORK," by inventors Somesh Gupta, Anoop Ghanwani,
Phanidhar Koganti, and Shunjia Yu, filed 16 Mar. 2010, the
disclosure of which is incorporated by reference herein.
[0088] The Ethernet NS provides the ability to distribute various
information across the VCS. The MAC information learned at one
member switch is distributed to all other member switches, which
facilitates fast MAC moves (for example, during migration of
virtual machines) and global MAC learning. In some embodiments,
layer-2 multicast information, which can be a multicast MAC address
with corresponding switch/port identifiers and VLAN tag, can be
distributed to facilitate efficient VCS-wide multicast. Optionally,
Ethernet NS provides a distribution mechanism and does not maintain
a central storage of the MAC-related knowledge base. In other
words, the Ethernet NS knowledge database is replicated and stored
distributively among all the VCS member switches.
[0089] Each member switch maintains a database of all the MAC
addresses learned throughout the VCS. This database can be used to
minimize the amount of flooding (a default behavior of Ethernet
switch when a frame's destination MAC address is not recognized).
Ethernet NS also provides VCS-wide distribution of multicast
MAC-to-RBridge/Port mapping information which can be obtained by
Internet Group Management Protocol (IGMP) snooping. (Details about
IGMP and IGMP snooping can be found at IETF RFC 3376 available at
http://tools.ietf.org/html/rfc3376 and IETF RFC 4541 available at
http://tools.ietf.org/html/rfc4541.) Ethernet NS distributes this
information to all RBridges, thereby allowing the VCS to behave as
a single switch. By tracking and forwarding IGMP join and leave
information, the Ethernet NS can efficiently track the multicast
MAC information and maintain an accurate layer-2 multicast
group.
[0090] One of the requirements of presenting a VCS as a single
switch is to support connection of trunked links from external
hosts to different RBridges within the VCS fabric. Such trunking
which involves connection to different RBridges is referred to as
multi-chassis trunking (MCT). Conceptually, support within the VCS
fabric for routing to a MCT destination is achieved by presenting
each MCT group (i.e., each trunk) as a virtual RBridge. In some
embodiments, the virtual RBridge is not assigned a domain ID and
thus does not utilize FSPF for routing setup. Instead, the a
primary RBridge hosting the MCT distributes the virtual RBridge ID
and the corresponding link state updates to the VCS fabric. The
primary RBridge is responsible for learning a new MAC via an MCT
and distributing the new MAC information to the VCS.
[0091] When an RBridge joins the VCS it will request a dump of the
local NS database from the remote RBridge. It will not respond to
individual updates from the remote RBridge until the DB dump has
been received. After the database is in sync between two RBridges,
individual changes are detected locally and pushed remotely. If a
local database receives domain unreachable it is responsible for
removing all records for that remote domain and doing any local
notification that this removal implies.
[0092] FIG. 10 illustrates an example of name service operation in
a VCS, in accordance with one embodiment of the present invention.
In this example, a VCS 1000 includes four member switches
(Rbridges), 1002, 1004, 1006, and 1008. Assume that an end host
1014 is coupled to switch 1002 during operation. When end host 1014
sends its first Ethernet frame, switch 1002 would not recognize the
source MAC address of this ingress frame. Upon receiving this
ingress frame, switch 1002 then determines the port (or interface)
on which the frame arrives and the frame's VLAG tag. Subsequently,
switch 1002 assembles an Ethernet NS update frame which indicates
the learned MAC address (which corresponds to end host 1014), its
switch identifier (which in one embodiment is the RBridge ID of
switch 1002), the port identifier, and the VLAG tag for the frame.
In one embodiment, this frame is an FC registered state change
notification (RSCN) encapsulated in a TRILL header. Note that
switch 1002 can obtain the information of all other member switches
in the VCS by looking up the global configuration database.
Subsequently, switch 1002 can send the Ethernet NS update frame to
switches 1004, 1008, and 1006, respectively. Upon receiving the
Ethernet NS update frame, each member switch updates its own MAC
database accordingly. In this way, when one of the member switches
receives an Ethernet frame destined to end-host 1014, it can
forward that frame to switch 1002 (instead of flooding the frame to
all of its ports).
[0093] Also shown in the example in FIG. 10 is an MCT group 1016.
MCT group 1016 is formed by an end host 1012 which is dual-homed
with switches 1006 and 1008. Assume that switch 1006 is the primary
RBridge in MCT group 1016. When end host 1012 and MCT group 1010 is
first configured, switch 1006 assigns a virtual RBridge 1010 to MCT
group 1010. In addition, switch 1006 notifies the rest of VCS 1000
about the MAC address of end host 1012. Note that the NS update
associated the MAC address of end host 1012 indicates the
identifier of virtual RBridge 1010 (instead of the identifier of
either switch 1006 or switch 1008). In this way, the rest of VCS
1000 can associate end host 1012 with virtual RBridge 1010. When
forwarding a frame destined to end host 1012, a member switch in
VCS 1000 would forward the frame toward virtual RBridge 1010 (i.e.,
by setting RBridge 1010 as the destination RBridge in the TRILL
header). Note that switch 1006 is also responsible for distributing
the link state information with respect to the virtual connectivity
between virtual RBridge 1010 and switches 1006 and 1008 (indicated
by the dotted lines).
[0094] In case when one of the links (i.e., either the link between
switch 1006 and end host 1012, or the link between switch 1008 and
end host 1012) fails, as part of the MCT NS, in one embodiment,
primary RBridge 1006 is responsible for updating the rest of the
VCS 1000 that host 1012's MAC address is no longer associated with
virtual RBidge 1010. Instead, the MAC address of host 1012 is now
associated with the switch to which host 1012 remains connected. In
a further embodiment, it can be the responsibility of the switch
that remains connected to host 1012 to distribute the updated MAC
address association to the rest of VCS 1000.
[0095] FIG. 11 presents a flowchart illustrating the process of
distributing learned MAC information by the Ethernet name service
in a VCS, in accordance with one embodiment of the present
invention. During operation, a VCS member switch detects an ingress
frame with a new source MAC address (operation 1102). The switch
then identifies the port on which the ingress frame is received
(operation 1104). Subsequently, the switch assembles an Ethernet NS
update frame with the learned MAC address, the switch identifier,
port identifier, and VLAN tag (operation 1106). The switch then
distributes the Ethernet NS update frames to all member switches in
the VCS (operation 1108).
[0096] FIG. 12 presents a flowchart illustrating the process of
distributing information of a learned MAC address via an MCT, in
accordance with one embodiment of the present invention. During
operation, assume that one of the switches in a MCT group detects
an ingress frame with a new source MAC address (operation 1202).
The switch then determines whether the end host which generates the
frame is dual-homed with the MCT group (operation 1204). In one
embodiment, the switch can make this determination by communicating
with the other switch of the MCT group. In a further embodiment,
the switch can inspect the link aggregation group (LAG) ID of the
ingress frame to determine whether the end host is transmitting
using a LAG. If the frame is an MCT frame, the switch then
assembles an Ethernet NS update frame with the MAC address, the
virtual RBridge identifier corresponding to the MCT, a port
identifier, and the VLAG tag of the frame (operation 1206).
[0097] If the frame is determined to be from a regular end host
(i.e., not a dual-homed host), the switch assembles an Ethernet NS
updated frame with the MAC address, the local physical switch
identifier (as opposed to the virtual RBridge ID), the identifier
of the port on which the frame is received, and the frame's VLAN
tag (operation 1207). The switch then distributes the Ethernet NS
update frames to all the member switches in the VCS (operation
1208).
[0098] FIG. 13 presents a flowchart illustrating the process of
updating the link state in an MCT group, in accordance with one
embodiment of the present invention. During operation, assume one
of the MCT partner switches detects a link or port failure which is
part of the MCT group (operation 1302). Note that this failure can
be detected locally (which means a port on the local switch or a
link coupled to a local port has failed), or be detected remotely
(which means that the failure occurs on the partner switch and the
local switch is notified of the failure by the partner switch). The
switch then determines whether the MCT end host is still connected
to the local switch (operation 1304). If the end host is no longer
connected to the local switch, the local switch optionally notifies
the other partner switch in the MCT of the failure (operation 1310)
and takes no further actions, assuming that the partner switch will
assume responsibility of updating the link state (using, for
example, the same procedure illustrated in FIG. 13).
[0099] If the MCT end host is still connected to the local switch,
the switch then assembles an NS update frame with the end host's
MAC address, the local switch's identifier (e.g., the physical
RBridge ID of the local switch), the identifier of the port thought
which the end host is connected, and the proper VLAN tag (operation
1306). The switch then distributes the NS update frames to all
member switches in the VCS (operation 1308).
Exemplary VCS Member Switch
[0100] FIG. 14 illustrates an exemplary switch that facilitates
formation of a virtual cluster switch with Ethernet and MCT name
services, in accordance with an embodiment of the present
invention. The VCS member switch is a TRILL RBridge 1400 running
special VCS software. RBridge 1400 includes a number of Ethernet
communication ports 1401, which can transmit and receive Ethernet
frames and/or TRILL encapsulated frames. Also included in RBridge
1400 is a packet processor 1402, a virtual FC switch management
module 1404, a logical FC switch 1405, a VCS configuration database
1406, a name services management module 1407, and a TRILL header
generation module 1408.
[0101] During operation, packet processor 1402 extracts the source
and destination MAC addresses of incoming frames, and attaches
proper Ethernet or TRILL headers to outgoing frames. Virtual FC
switch management module 1404 maintains the state of logical FC
switch 1405, which is used to join other VCS switches using the FC
switch fabric protocols. VCS configuration database 1406 maintains
the configuration state of every switch within the VCS. TRILL
header generation module 1408 is responsible for generating
property TRILL headers for frames that are to be transmitted to
other VCS member switches. Based on the extracted MAC addresses of
incoming frames, NS management module 1407 distributes the NS
update frames to the rest of the VCS. NS management module 1407
also maintains a copy of NS database 1409. NS database 1409 stores
all the learned MAC address information from every member switch in
the VCS.
[0102] The methods and processes described herein can be embodied
as code and/or data, which can be stored in a computer-readable
non-transitory storage medium. When a computer system reads and
executes the code and/or data stored on the computer-readable
non-transitory storage medium, the computer system performs the
methods and processes embodied as data structures and code and
stored within the medium.
[0103] The methods and processes described herein can be executed
by and/or included in hardware modules or apparatus. These modules
or apparatus may include, but are not limited to, an
application-specific integrated circuit (ASIC) chip, a
field-programmable gate array (FPGA), a dedicated or shared
processor that executes a particular software module or a piece of
code at a particular time, and/or other programmable-logic devices
now known or later developed. When the hardware modules or
apparatus are activated, they perform the methods and processes
included within them.
[0104] The foregoing descriptions of embodiments of the present
invention have been presented only for purposes of illustration and
description. They are not intended to be exhaustive or to limit
this disclosure. Accordingly, many modifications and variations
will be apparent to practitioners skilled in the art. The scope of
the present invention is defined by the appended claims.
* * * * *
References