draft-cheng-mpls-tp-shared-ring-protection-05.txt   draft-cheng-mpls-tp-shared-ring-protection-06.txt 
Network Working Group W. Cheng Network Working Group W. Cheng
Internet-Draft L. Wang Internet-Draft L. Wang
Intended status: Standards Track H. Li Intended status: Standards Track H. Li
Expires: December 19, 2015 China Mobile Expires: February 12, 2016 China Mobile
H. Helvoort H. Helvoort
Hai Gaoming BV Hai Gaoming BV
K. Liu K. Liu
J. Dong J. Dong
J. He J. He
Huawei Technologies Huawei Technologies
F. Li F. Li
China Academy of Telecommunication Research, MIIT., China China Academy of Telecommunication Research, MIIT., China
J. Yang J. Yang
ZTE Corporation P.R.China ZTE Corporation P.R.China
J. Wang J. Wang
Fiberhome Telecommunication Technologies Co., LTD. Fiberhome Telecommunication Technologies Co., LTD.
June 17, 2015 August 11, 2015
MPLS-TP Shared-Ring protection (MSRP) mechanism for ring topology MPLS-TP Shared-Ring protection (MSRP) mechanism for ring topology
draft-cheng-mpls-tp-shared-ring-protection-05 draft-cheng-mpls-tp-shared-ring-protection-06
Abstract Abstract
This document describes requirements, architecture and solutions for This document describes requirements, architecture and solutions for
MPLS-TP Shared Ring Protection (MSRP) in the ring topology for point- MPLS-TP Shared Ring Protection (MSRP) in the ring topology for point-
to-point (P2P) services. The mechanism of MSRP is illustrated and to-point (P2P) services. The mechanism of MSRP is illustrated and
how it satisfies the requirements in RFC 5654 for optimized ring how it satisfies the requirements for optimized ring protection in
protection is analyzed. RFC 5654 is analyzed. This document also defines the Ring Protection
Switch (RPS) Protocol which is used to coordinate the protection
behavior of the nodes on MPLS ring.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 19, 2015. This Internet-Draft will expire on February 12, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3. Terminology and Notation . . . . . . . . . . . . . . . . . . 5 3. Terminology and Notation . . . . . . . . . . . . . . . . . . 5
4. Shared Ring Protection Architecture . . . . . . . . . . . . . 5 4. Shared Ring Protection Architecture . . . . . . . . . . . . . 5
4.1. Ring Tunnel . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Ring Tunnel . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. Establishment of Ring Tunnel . . . . . . . . . . . . 6 4.1.1. Establishment of Ring Tunnel . . . . . . . . . . . . 6
4.1.2. Label Assignment and Distribution . . . . . . . . . . 8 4.1.2. Label Assignment and Distribution . . . . . . . . . . 8
4.1.3. Forwarding Operation . . . . . . . . . . . . . . . . 8 4.1.3. Forwarding Operation . . . . . . . . . . . . . . . . 8
4.2. Failure Detection . . . . . . . . . . . . . . . . . . . . 9 4.2. Failure Detection . . . . . . . . . . . . . . . . . . . . 9
4.3. Ring Protection . . . . . . . . . . . . . . . . . . . . . 10 4.3. Ring Protection . . . . . . . . . . . . . . . . . . . . . 10
4.3.1. Wrapping . . . . . . . . . . . . . . . . . . . . . . 10 4.3.1. Wrapping . . . . . . . . . . . . . . . . . . . . . . 10
4.3.2. Short Wrapping . . . . . . . . . . . . . . . . . . . 12 4.3.2. Short Wrapping . . . . . . . . . . . . . . . . . . . 12
4.3.3. Steering . . . . . . . . . . . . . . . . . . . . . . 13 4.3.3. Steering . . . . . . . . . . . . . . . . . . . . . . 14
4.4. Interconnected Ring Protection . . . . . . . . . . . . . 16 4.4. Interconnected Ring Protection . . . . . . . . . . . . . 17
4.4.1. Interconnected Ring Topology . . . . . . . . . . . . 16 4.4.1. Interconnected Ring Topology . . . . . . . . . . . . 17
4.4.2. Interconnected Ring Protection Mechanisms . . . . . . 17 4.4.2. Interconnected Ring Protection Mechanisms . . . . . . 18
4.4.3. Ring Tunnels in Interconnected Rings . . . . . . . . 18 4.4.3. Ring Tunnels in Interconnected Rings . . . . . . . . 19
4.4.4. Interconnected Ring Switching Procedure . . . . . . . 20 4.4.4. Interconnected Ring Switching Procedure . . . . . . . 21
4.4.5. Interconnected Ring Detection Mechanism . . . . . . . 21 4.4.5. Interconnected Ring Detection Mechanism . . . . . . . 22
5. Ring Protection Coordination Protocol . . . . . . . . . . . . 22 5. Ring Protection Coordination Protocol . . . . . . . . . . . . 23
5.1. RPS Protocol . . . . . . . . . . . . . . . . . . . . . . 23 5.1. RPS Protocol . . . . . . . . . . . . . . . . . . . . . . 24
5.1.1. Transmission and Acceptance of RPS Requests . . . . . 25 5.1.1. Transmission and Acceptance of RPS Requests . . . . . 26
5.1.2. RPS PDU Format . . . . . . . . . . . . . . . . . . . 25 5.1.2. RPS PDU Format . . . . . . . . . . . . . . . . . . . 26
5.1.3. Ring Node RPS States . . . . . . . . . . . . . . . . 26 5.1.3. Ring Node RPS States . . . . . . . . . . . . . . . . 27
5.1.4. RPS State Transitions . . . . . . . . . . . . . . . . 28 5.1.4. RPS State Transitions . . . . . . . . . . . . . . . . 29
5.2. RPS State Machine . . . . . . . . . . . . . . . . . . . . 30 5.2. RPS State Machine . . . . . . . . . . . . . . . . . . . . 31
5.2.1. Initial States . . . . . . . . . . . . . . . . . . . 30 5.2.1. Initial States . . . . . . . . . . . . . . . . . . . 31
5.2.2. State transitions When Local Request is Applied . . . 31 5.2.2. State transitions When Local Request is Applied . . . 32
5.2.3. State Transitions When Remote Request is Applied . . 35 5.2.3. State Transitions When Remote Request is Applied . . 36
5.2.4. State Transitions When Request Addresses to Another 5.2.4. State Transitions When Request Addresses to Another
Node is Received . . . . . . . . . . . . . . . . . . 38 Node is Received . . . . . . . . . . . . . . . . . . 39
5.3. RPS and PSC Comparison on Ring Topology . . . . . . . . . 40 5.3. RPS and PSC Comparison on Ring Topology . . . . . . . . . 41
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
7. Security Considerations . . . . . . . . . . . . . . . . . . . 42 6.1. G-ACh Channel Type . . . . . . . . . . . . . . . . . . . 42
8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 42 6.2. RSP Request Codes . . . . . . . . . . . . . . . . . . . . 43
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 7. Security Considerations . . . . . . . . . . . . . . . . . . . 43
9.1. Normative References . . . . . . . . . . . . . . . . . . 42 8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 43
9.2. Informative References . . . . . . . . . . . . . . . . . 42 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 44
10.1. Normative References . . . . . . . . . . . . . . . . . . 44
10.2. Informative References . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction 1. Introduction
As described in 2.5.6.1 of [RFC5654], Ring Protection of MPLS-TP As described in 2.5.6.1 of [RFC5654], Ring Protection of MPLS-TP
requirements , several service providers have expressed much interest requirements , several service providers have expressed much interest
in operating MPLS-TP in ring topologies and require a high-level in operating MPLS-TP in ring topologies and require a high-level
survivability function in these topologies. In operational transport survivability function in these topologies. In operational transport
network deployment, MPLS-TP networks are often constructed with ring network deployment, MPLS-TP networks are often constructed with ring
topologies. It calls for an efficient and optimized ring protection topologies. It calls for an efficient and optimized ring protection
mechanism to achieve simple operation and fast, sub 50 ms, recovery mechanism to achieve simple operation and fast, sub 50 ms, recovery
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o Several nodes share one power supply system o Several nodes share one power supply system
o Weather sensitive micro-wave system o Weather sensitive micro-wave system
Once one of the above risk factors happens, multiple links or nodes Once one of the above risk factors happens, multiple links or nodes
failures may occur simultaneously and those failed links or nodes may failures may occur simultaneously and those failed links or nodes may
be located on a single ring as well as on interconnected rings. Ring be located on a single ring as well as on interconnected rings. Ring
protection against multiple failures should cover both multiple protection against multiple failures should cover both multiple
failures on a single ring and multiple failures on interconnected failures on a single ring and multiple failures on interconnected
rings. rings, as long as the connectivity between the ingress and egress
node of the ring still exists.
2.2. Smooth Upgrade from Linear Protection to Ring Protection 2.2. Smooth Upgrade from Linear Protection to Ring Protection
It is beneficial for service providers to upgrade the protection It is beneficial for service providers to upgrade the protection
scheme from linear protection to ring protection in their MPLS-TP scheme from linear protection to ring protection in their MPLS-TP
network without service interruption. In-service insertion and network without service interruption. In-service insertion and
removal of a node on the ring should also be supported. Therefore, removal of a node on the ring should also be supported. Therefore,
the MPLS-TP ring protection mechanism is supposed to be developed and the MPLS-TP ring protection mechanism is supposed to be developed and
optimized for compliance with this smooth upgrading principle. optimized for compliance with this smooth upgrading principle.
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| LSP Label | | LSP Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Label | | PW Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload | | Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Label stack used in MPLS-TP Shared Ring Protection Figure 2. Label stack used in MPLS-TP Shared Ring Protection
4.1.1. Establishment of Ring Tunnel 4.1.1. Establishment of Ring Tunnel
The Ring tunnels are established based on the exit node. The exit The Ring tunnels are established based on the egress node. The
node is the node where traffic leaves the ring. LSPs which have the egress node is the node where traffic leaves the ring. LSPs which
same exit node on the ring share the same ring tunnels. In other have the same egress node on the ring share the same ring tunnels.
words, all the LSPs that traverse the ring and exit from the same In other words, all the LSPs that traverse the ring and exit from the
node share the same working ring tunnel and protection ring tunnel. same node share the same working ring tunnel and protection ring
For each exit node, four ring tunnels are established: tunnel. For each egress node, four ring tunnels are established:
o one clockwise working ring tunnel, which is protected by the o one clockwise working ring tunnel, which is protected by the
anticlockwise protection ring tunnel anticlockwise protection ring tunnel
o one anticlockwise protection ring tunnel o one anticlockwise protection ring tunnel
o one anticlockwise working ring tunnel, which is protected by the o one anticlockwise working ring tunnel, which is protected by the
clockwise protection ring tunnel clockwise protection ring tunnel
o one clockwise protection ring tunnel o one clockwise protection ring tunnel
The structure of the protection tunnels are determined by the The structure of the protection tunnels are determined by the
selected protection mechanism. This will be detailed in subsequent selected protection mechanism. This will be detailed in subsequent
sections. sections.
As shown in Figure 3, LSP 1, LSP 2 and LSP 3 enter the ring from Node As shown in Figure 3, LSP1, LSP2 and LSP3 enter the ring from Node E,
E, Node A and Node B, respectively, and all leave the ring at Node D. Node A and Node B, respectively, and all leave the ring at Node D.
To protect these LSPs that traverse the ring, a clockwise working To protect these LSPs that traverse the ring, a clockwise working
ring tunnel (RcW_D) via E->F->A->B->C->D, and its anticlockwise ring tunnel (RcW_D) via E->F->A->B->C->D, and its anticlockwise
protection ring tunnel (RaP_D) via D->C->B->A->F->E->D are protection ring tunnel (RaP_D) via D->C->B->A->F->E->D are
established, Also, an anti-clockwise working ring tunnel (RaW_D) via established, Also, an anti-clockwise working ring tunnel (RaW_D) via
C->B->A->F->E->D, and its clockwise protection ring tunnel (RcP_D) C->B->A->F->E->D, and its clockwise protection ring tunnel (RcP_D)
via D->E->F->A->B->C->D are established. For simplicity Figure 3 via D->E->F->A->B->C->D are established. For simplicity Figure 3
only shows RcW_D and RaP_D. A similar provisioning should be applied only shows RcW_D and RaP_D. A similar provisioning should be applied
for any other node on the ring. In summary, for each node in for any other node on the ring. In summary, for each node in
Figure 3 when acting as exit node, the ring tunnels are created as Figure 3 when acting as egress node, the ring tunnels are created as
follows: follows:
o To Node A: RcW_A, RaW_A, RcP_A, RaP_A o To Node A: RcW_A, RaW_A, RcP_A, RaP_A
o To Node B: RcW_B, RaW_B, RcP_B, RaP_B o To Node B: RcW_B, RaW_B, RcP_B, RaP_B
o To Node C: RcW_C, RaW_C, RcP_C, RaP_C o To Node C: RcW_C, RaW_C, RcP_C, RaP_C
o To Node D: RcW_D, RaW_D, RcP_D, RaP_D o To Node D: RcW_D, RaW_D, RcP_D, RaP_D
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LSP2 +---+#############+---+ LSP2 +---+#############+---+
LSP3 LSP3
---- physical links ---- physical links
**** RcW_D **** RcW_D
#### RaP_D #### RaP_D
Figure 3. Ring tunnels in MSRP Figure 3. Ring tunnels in MSRP
Through these working and protection ring tunnels, LSPs which enter Through these working and protection ring tunnels, LSPs which enter
the ring from any node can reach any exit nodes on the ring, and are the ring from any node can reach any egress nodes on the ring, and
protected from failures on the ring. are protected from failures on the ring.
4.1.2. Label Assignment and Distribution 4.1.2. Label Assignment and Distribution
The ring tunnel labels are downstream-assigned labels as defined in The ring tunnel labels are downstream-assigned labels as defined in
[RFC3031]. The ring tunnel labels can be either configured [RFC3031]. The ring tunnel labels can be either configured
statically, provisioned by a controller, or distributed dynamically statically, provisioned by a controller, or distributed dynamically
via a control protocol. via a control protocol.
4.1.3. Forwarding Operation 4.1.3. Forwarding Operation
When an MPLS-TP transport path, such as an LSP, enters the ring, the When an MPLS-TP transport path, such as an LSP, enters the ring, the
ingress node on the ring pushes the working ring tunnel label ingress node on the ring pushes the working ring tunnel label
according to the exit node and sends the traffic to the next hop. according to the egress node and sends the traffic to the next hop.
The transit nodes on the working ring tunnel swap the ring tunnel The transit nodes on the working ring tunnel swap the ring tunnel
labels and forward the packets to the next hop. When the packet labels and forward the packets to the next hop. When the packet
arrives at the exit node, the exit node pops the ring tunnel label arrives at the egress node, the egress node pops the ring tunnel
and forwards the packets based on the inner LSP label and PW label. label and forwards the packets based on the inner LSP label and PW
Figure 4 shows the label operation in the MPLS-TP shared ring label. Figure 4 shows the label operation in the MPLS-TP shared ring
protection mechanism. Assume that LSP1 enters the ring at Node A and protection mechanism. Assume that LSP1 enters the ring at Node A and
exits from Node D, and the following label operations are executed. exits from Node D, and the following label operations are executed.
1. Ingress node: Packets of LSP1 arrive at Node A with a label stack 1. Ingress node: Packets of LSP1 arrive at Node A with a label stack
[LSP1] and is supposed to be forwarded in the clockwise direction [LSP1] and is supposed to be forwarded in the clockwise direction
of the ring. The clockwise working ring tunnel label RcW_D will of the ring. The clockwise working ring tunnel label RcW_D will
be pushed at Node A, the label stack for the forwarded packet at be pushed at Node A, the label stack for the forwarded packet at
Node A is changed to [RcW_D(B)|LSP1]. Node A is changed to [RcW_D(B)|LSP1].
2. Transit nodes: In this case, Node B and Node C forward the 2. Transit nodes: In this case, Node B and Node C forward the
packets by swapping the working ring tunnel labels. For example, packets by swapping the working ring tunnel labels. For example,
the label [RcW_D(B)|LSP1] is swapped to [RcW_D(C)|LSP1] at Node the label [RcW_D(B)|LSP1] is swapped to [RcW_D(C)|LSP1] at Node
B. B.
3. Exit node: When the packet arrives at Node D (i.e. the exit node) 3. Egress node: When the packet arrives at Node D (i.e. the egress
with label stack [RcW_D(D)|LSP1], Node D pops RcW_D(D), and node) with label stack [RcW_D(D)|LSP1], Node D pops RcW_D(D), and
subsequently deals with the inner labels of LSP1. subsequently deals with the inner labels of LSP1.
4. All the LSPs that exit from the same node share the same set of
ring tunnel labels.
+---+#####[RaP_D(F)]######+---+ +---+#####[RaP_D(F)]######+---+
| F |---------------------| A | +-- LSP1 | F |---------------------| A | +-- LSP1
+---+*****[RcW_D(A)]******+---+ +---+*****[RcW_D(A)]******+---+
#/* *\# #/* *\#
[RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#[RaP_D(A)] [RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#[RaP_D(A)]
#/* *\# #/* *\#
+---+ +---+ +---+ +---+
| E | | B | | E | | B |
+---+ +---+ +---+ +---+
#\ */# #\ */#
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Figure 4. Label operation of MSRP Figure 4. Label operation of MSRP
4.2. Failure Detection 4.2. Failure Detection
The MPLS-TP section layer OAM is used to monitor the connectivity The MPLS-TP section layer OAM is used to monitor the connectivity
between each two adjacent nodes on the ring using the mechanisms between each two adjacent nodes on the ring using the mechanisms
defined in [RFC6371]. Protection switching is triggered by the defined in [RFC6371]. Protection switching is triggered by the
failure detected on the ring by the OAM mechanisms. failure detected on the ring by the OAM mechanisms.
Two end ports of a link form a Maintenance Entity Group (MEG), and an Two end ports of a link form a Maintenance Entity Group (MEG), and an
MEG end point (MEP) function is installed in each ring port. CC-V MEG end point (MEP) function is installed in each ring port. CC OAM
OAM packets are periodically exchanged between each pair of MEPs to packets are periodically exchanged between each pair of MEPs to
monitor the link health. Three or more consecutive CC-V packets monitor the link health. Three consecutive CC packets losses will be
losses will be interpreted as a link failure. interpreted as a link failure.
A node failure is regarded as the failure of two links attached to A node failure is regarded as the failure of two links attached to
that node. The two nodes adjacent to the failed node detect the that node. The two nodes adjacent to the failed node detect the
failure in the links that are connected to the failed node. failure in the links that are connected to the failed node.
4.3. Ring Protection 4.3. Ring Protection
This section specifies the ring protection mechanisms in detail. In This section specifies the ring protection mechanisms in detail. In
general, the description uses the clockwise working ring tunnel and general, the description uses the clockwise working ring tunnel and
the corresponding anti-clockwise protection ring tunnel as example, the corresponding anti-clockwise protection ring tunnel as example,
but the mechanism is applicable in the same way to the anti-clockwise but the mechanism is applicable in the same way to the anti-clockwise
working and clockwise protection ring tunnels. working and clockwise protection ring tunnels.
Taking the topology in Figure 4 as example, the LSP1 enters the ring Taking the topology in Figure 4 as example, the LSP1 enters the ring
at Node A and leaves the ring at Node D. In normal state, LSP 1 is at Node A and leaves the ring at Node D. In normal state, LSP1 is
carried by clockwise working ring tunnel (RcW_D) through the path carried by clockwise working ring tunnel (RcW_D) through the path
A->B->C->D, the label operation is: A->B->C->D, the label operation is:
[LSP1](original data traffic carried by LSP 1) -> [LSP1](original data traffic carried by LSP1) ->
[RCW_D(B)|LSP1](NodeA) -> [RCW_D(C)|LSP1](NodeB) -> [RCW_D(D)| [RCW_D(B)|LSP1](NodeA) -> [RCW_D(C)|LSP1](NodeB) -> [RCW_D(D)|
LSP1](NodeC) -> [LSP1](data traffic carried by LSP 1). Then at node LSP1](NodeC) -> [LSP1](data traffic carried by LSP1). Then at node D
D the packet will be forwarded based on label stack of LSP1. the packet will be forwarded based on label stack of LSP1.
The following sections describes the protection mechanisms used in The following sections describes the protection mechanisms used in
ring topology. ring topology.
4.3.1. Wrapping 4.3.1. Wrapping
With the wrapping mechanism, the protection ring tunnel is a closed With the wrapping mechanism, the protection ring tunnel is a closed
ring identified by the exit node. As shown in Figure 4, the RaP_D is ring identified by the egress node. As shown in Figure 4, the RaP_D
the anticlockwise protection ring tunnel for the clockwise working is the anticlockwise protection ring tunnel for the clockwise working
ring tunnel RcW_D. As specified in the following sections, the ring tunnel RcW_D. As specified in the following sections, the
closed ring protection tunnel can protect both the link failure and closed ring protection tunnel can protect both the link failure and
the node failure. the node failure.
4.3.1.1. Wrapping for Link Failure 4.3.1.1. Wrapping for Link Failure
When a link failure between Node B and Node C occurs, if it is a bi- When a link failure between Node B and Node C occurs, if it is a bi-
directional failure, both Node B and Node C can detect the failure directional failure, both Node B and Node C can detect the failure
via OAM mechanism; if it is a uni-directional failure, one of the two via OAM mechanism; if it is a uni-directional failure, one of the two
nodes would detect the failure and it would inform the other node via nodes would detect the failure and it would inform the other node via
the Ring Protection Switch Protocol (RPS) which is specified in the Ring Protection Switch Protocol (RPS) which is specified in
section 5. Then Node B switches the clockwise working ring tunnel section 5. Then Node B switches the clockwise working ring tunnel
(RcW_D) to the anticlockwise protection ring tunnel (RaP_D) and Node (RcW_D) to the anticlockwise protection ring tunnel (RaP_D) and Node
C switches anticlockwise protection ring tunnel(RaP_D) to the C switches anticlockwise protection ring tunnel(RaP_D) to the
clockwise working ring tunnel(RcW_D). The data traffic which enters clockwise working ring tunnel(RcW_D). The data traffic which enters
the ring at Node A and exits at Node D follows the path the ring at Node A and leaves the ring at Node D follows the path
A->B->A->F->E->D->C->D. The label operation is: A->B->A->F->E->D->C->D. The label operation is:
[LSP1](Original data traffic) -> [RcW_D(B)|LSP1](Node A) -> [LSP1](Original data traffic) -> [RcW_D(B)|LSP1](Node A) ->
[RaP_D(A)|LSP1](Node B) -> [RaP_D(F)|LSP1](Node A) -> [RaP_D(E)|LSP1] [RaP_D(A)|LSP1](Node B) -> [RaP_D(F)|LSP1](Node A) -> [RaP_D(E)|LSP1]
(Node F) -> [RaP_D(D)|LSP1] (Node E) -> [RaP_D(C)|LSP1] (Node D) -> (Node F) -> [RaP_D(D)|LSP1] (Node E) -> [RaP_D(C)|LSP1] (Node D) ->
[RcW_D(D)|LSP1](Node C) -> [LSP1](data traffic exits the ring). [RcW_D(D)|LSP1](Node C) -> [LSP1](data traffic leaves the ring).
+---+#####[RaP_D(F)]######+---+ +---+#####[RaP_D(F)]######+---+
| F |---------------------| A | +-- LSP1 | F |---------------------| A | +-- LSP1
+---+*****[RcW_D(A)]******+---+ +---+*****[RcW_D(A)]******+---+
#/* *\# #/* *\#
[RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#RaP_D(A) [RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#RaP_D(A)
#/* *\# #/* *\#
+---+ +---+ +---+ +---+
| E | | B | | E | | B |
+---+ +---+ +---+ +---+
skipping to change at page 11, line 35 skipping to change at page 11, line 33
LSP1 +-- | D |-------------------| C | LSP1 +-- | D |-------------------| C |
+---+#####[RaP_D(C)]####+---+ +---+#####[RaP_D(C)]####+---+
-----physical links xxxx Failure Link -----physical links xxxx Failure Link
****** RcW_D ###### RaP_D ****** RcW_D ###### RaP_D
Figure 5.Wrapping for link failure Figure 5.Wrapping for link failure
4.3.1.2. Wrapping for Node Failure 4.3.1.2. Wrapping for Node Failure
When Node B fails, Node A detects the failure between A and B and As shown in Figure 6, when Node B fails, Node A detects the failure
switches the clockwise work ring tunnel (RcW_D) to the anticlockwise between A and B and switches the clockwise work ring tunnel (RcW_D)
protection ring tunnel(RaP_D), Node C detects the failure between C to the anticlockwise protection ring tunnel (RaP_D), Node C detects
and B and switches the anticlockwise protection ring tunnel(RaP_D) to the failure between C and B and switches the anticlockwise protection
the clockwise working ring tunnel(RcW_D). The data traffic which ring tunnel (RaP_D) to the clockwise working ring tunnel (RcW_D).
enters the ring at Node A and exits at Node D follows the path The data traffic which enters the ring at Node A and exits at Node D
A->F->E->D->C->D. The label operation is: follows the path A->F->E->D->C->D. The label operation is:
[LSP1](original data traffic carried by LSP 1) -> [LSP1](original data traffic carried by LSP1) ->
[RaP_D(F)|LSP1](NodeA) -> [RaP_D(E)|LSP1](NodeF) -> [RaP_D(F)|LSP1](NodeA) -> [RaP_D(E)|LSP1](NodeF) ->
[RaP_D(D)|LSP1](NodeE) -> [RaP_D(C)|LSP1] (NodeD) -> [RcW_D(D)|LSP1] [RaP_D(D)|LSP1](NodeE) -> [RaP_D(C)|LSP1] (NodeD) -> [RcW_D(D)|LSP1]
(NodeC) -> [LSP1](data traffic carried by LSP 1). (NodeC) -> [LSP1](data traffic carried by LSP1).
In one special case where node D fails, all the ring tunnels with
node D as egress will become unusable. However, before the failure
location is propagated to all the ring nodes, the wrapping protection
mechanism may cause temporary traffic loop: node C detects the
failure and switches the traffic from the clockwise work ring tunnel
(RcW_D) to the anticlockwise protection ring tunnel (RaP_D), node E
also detects the failure and would switch the traffic from
anticlockwise protection ring tunnel (RaP_D) back to the clockwise
work ring tunnel (RcW_D). A possible mechanism to mitigate the
temporary loop problem is: the TTL of the ring tunnel label is set to
2*N by the ingress ring node of the traffic, where N is the number of
nodes on the ring.
+---+#####[RaP_D(F)]######+---+ +---+#####[RaP_D(F)]######+---+
| F |---------------------| A | +-- LSP1 | F |---------------------| A | +-- LSP1
+---+*****[RcW_D(A)]******+---+ +---+*****[RcW_D(A)]******+---+
#/* *\# #/* *\#
[RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#RaP_D(A) [RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#RaP_D(A)
#/* *\# #/* *\#
+---+ xxxxx +---+ xxxxx
| E | x B x | E | x B x
+---+ xxxxx +---+ xxxxx
skipping to change at page 12, line 35 skipping to change at page 12, line 40
4.3.2. Short Wrapping 4.3.2. Short Wrapping
With the traditional wrapping protection scheme, Protection switching With the traditional wrapping protection scheme, Protection switching
is executed at both nodes detecting the failure, consequently the is executed at both nodes detecting the failure, consequently the
traffic will be wrapped twice. This mechanism will cause additional traffic will be wrapped twice. This mechanism will cause additional
latency and bandwidth consumption when traffic is switched to the latency and bandwidth consumption when traffic is switched to the
protection path. protection path.
With short wrapping protection, data traffic switching is executed With short wrapping protection, data traffic switching is executed
only at the upstream node detecting the link failure, and exits the only at the upstream node detecting the failure, and data traffic
ring in the protection ring tunnel at the exit node. This scheme can leaves the ring in the protection ring tunnel at the egress node.
reduce the additional latency and bandwidth consumption when traffic This scheme can reduce the additional latency and bandwidth
is switched to the protection path. consumption when traffic is switched to the protection path.
In the traditional wrapping solution, the protection ring tunnel is a In the traditional wrapping solution, the protection ring tunnel is a
closed ring in normal state, while in the short wrapping solution, closed ring in normal state, while in the short wrapping solution,
the protection ring tunnel is ended at the exit node, which is the protection ring tunnel is ended at the egress node, which is
similar to the working ring tunnel. Short wrapping is easy to similar to the working ring tunnel. Short wrapping is easy to
implement in shared ring protection because both the working and implement in shared ring protection because both the working and
protection ring tunnels are terminated on the exit nodes. Figure 7 protection ring tunnels are terminated on the egress nodes. Figure 7
shows the clockwise working ring tunnel and the anticlockwise shows the clockwise working ring tunnel and the anticlockwise
protection ring tunnel with node D as the exit node. protection ring tunnel with node D as the egress node.
As shown in Figure 7, in normal state, LSP 1 is carried by the 4.3.2.1. Short Wrapping for Link Failure
As shown in Figure 7, in normal state, LSP1 is carried by the
clockwise working ring tunnel (RcW_D) through the path A->B->C->D. clockwise working ring tunnel (RcW_D) through the path A->B->C->D.
When a link failure between Node B and Node C occurs, Node B switches When a link failure between Node B and Node C occurs, Node B switches
The working ring tunnel RcW_D to the protection ring tunnel RaP_D in The working ring tunnel RcW_D to the protection ring tunnel RaP_D in
the opposite direction. The difference occurs in the protection ring the opposite direction. The difference occurs in the protection ring
tunnel at exit node. In short wrapping protection, Rap_D ends in tunnel at egress node. In short wrapping protection, Rap_D ends in
Node D and then traffic will be forwarded based on the LSP labels. Node D and then traffic will be forwarded based on the LSP labels.
Thus with short wrapping mechanism, LSP1 will follow the path Thus with short wrapping mechanism, LSP1 will follow the path
A->B->A->F->E->D when link failure between Node B and Node C happens. A->B->A->F->E->D when link failure between Node B and Node C happens.
For node failure, the protection with short wrapping is similar to For node failure, the protection with short wrapping is similar to
the mechanism with link failure. the mechanism with link failure.
+---+#####[RaP_D(F)]######+---+ +---+#####[RaP_D(F)]######+---+
| F |---------------------| A | +-- LSP1 | F |---------------------| A | +-- LSP1
+---+*****[RcW_D(A)]******+---+ +---+*****[RcW_D(A)]******+---+
#/* *\# #/* *\#
skipping to change at page 13, line 33 skipping to change at page 13, line 42
#\ *x# #\ *x#
+---+*****[RcW_D(D)]****+---+ +---+*****[RcW_D(D)]****+---+
LSP1 +-- | D |-------------------| C | LSP1 +-- | D |-------------------| C |
+---+ +---+ +---+ +---+
----- physical links xxxxx Failure Link ----- physical links xxxxx Failure Link
****** RcW_D ###### RaP_D ****** RcW_D ###### RaP_D
Figure 7. Short wrapping for link failure Figure 7. Short wrapping for link failure
4.3.2.2. Short Wrapping for Node Failure
For the failure scenarios which happen on a non-egress node, short
wrapping protection switching is similar to the link failure as
described in the previous section. This section specifies the
scenario of egress node failure.
As shown in Figure 8, LSP1 enters the ring on node A, and leaves the
ring on node D. in normal state, LSP1 is carried by the clockwise
working ring tunnel (RcW_D) through the path A->B->C->D. When node D
fails, traffic of LSP1 cannot be protected by any ring tunnels which
use node D as the egress node. However, before the failure location
is propagated to all the ring nodes, node C switches all the traffic
on the working ring tunnel RcW_D to the protection ring tunnel RaP_D
in the opposite direction. When the traffic arrives at node E which
also detects the failure of node D, the protection ring tunnel RaP_D
cannot be used to forward traffic to node D. Since with short
wrapping mechanism, protection switching can only be performed once
from the working ring tunnel to the protection ring tunnel, thus node
E MUST NOT switch the traffic which is already carried on the
protection ring tunnel back to the working ring tunnel in the
opposite direction. Instead, node E will discard the traffic
received on RaP_D locally. This can avoid the temporary traffic loop
when the faiulre happens on the egress node of the ring tunnel. This
also illustrates one of the benefits of having separate working and
protection ring tunnels in each ring direction.
+---+#####[RaP_D(F)]######+---+
| F |---------------------| A | +-- LSP1
+---+*****[RcW_D(A)]******+---+
#/* *\#
[RaP_D(E)]#/*[RcW_D(F)] [RcW_D(B)]*\#RaP_D(A)
#/* *\#
+---+ +---+
| E | | B |
+---+ +---+
#\ */#
[RaP_D(D)]#\ [RcW_D(C)]*/#RaP_D(B)
#\ */#
xxxxx*****[RcW_D(D)]****+---+
LSP1 +-- x D x-------------------| C |
xxxxx +---+
-----physical links xxxxxx Failure Node
*****RcW_D ###### RaP_D
Figure 8. Short Wrapping for egress node failure
4.3.3. Steering 4.3.3. Steering
In ring topology, each working ring tunnel is associated with a In ring topology, each working ring tunnel is associated with a
protection ring tunnel in the opposite direction, and every node can protection ring tunnel in the opposite direction, and every node can
obtain the ring topology either by configuration or via some topology obtain the ring topology either by configuration or via some topology
discovery mechanism. When a failure occurs in the ring, the nodes discovery mechanism. The ring topology and the connectivity (Intact
that detect the failure will transmit the failure information in the or Severed) between the adjacent ring nodes form the ring map. Every
opposite direction of the failure hop by hop on the ring. When a ring node maintains its ring map. When a failure occurs in the ring,
node receives the message that identifies a failure, it can quickly the nodes that detect the failure via OAM mechanism will transmit the
determine the location of the fault by using the topology information failure information in the opposite direction of the failure hop by
that is maintained by the node, then it can determine whether the hop along the ring. When a node receives the message that identifies
a failure, it can quickly determine the location of the fault by
using the topology information that is maintained by the node and
upate the ring map accordingly, then it can determine whether the
LSPs entering the ring locally need to switchover or not. For LSPs LSPs entering the ring locally need to switchover or not. For LSPs
that needs to switchover, it will switch the LSPs from the working that needs to switchover, it will switch the LSPs from the working
ring tunnels to its corresponding protection ring tunnels. ring tunnels to its corresponding protection ring tunnels.
+--LSP l Ring map of F +--LSPl
+-+-+-+-+-+-+-+ +---+ ###[RaP_D(F)]### +---/ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ ###[RaP_D(F)]### +---/ +-+-+-+-+-+-+-+
|F|A|B|C|D|E|F| | F | ---------------- | A | |A|B|C|D|E|F|A| |F|A|B|C|D|E|F| | F | ---------------- | A | |A|B|C|D|E|F|A|
+-+-+-+-+-+-+-+ +---+ ***[RcW_D(A)]*** +---+ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ ***[RcW_D(A)]*** +---+ +-+-+-+-+-+-+-+
|I|I|I|S|I|I| |I|I|S|I|I|I| |I|I|I|S|I|I| |I|I|S|I|I|I|
+-+-+-+-+-+-+ #/* *\# +-+-+-+-+-+-+ +-+-+-+-+-+-+ #/* *\# +-+-+-+-+-+-+
[RaP_D(E)] #/* [RcW_D(B)] *\# [RaP_D(A)] [RaP_D(E)] #/* [RcW_D(B)] *\# [RaP_D(A)]
#/* [RcW_D(F)] *\# #/* [RcW_D(F)] *\#
+-+-+-+-+-+-+-+ #/* *\# +-+-+-+-+-+-+-+ #/* *\#
|E|F|A|B|C|D|E| +---+ +---+ +-- LSP 2 |E|F|A|B|C|D|E| +---+ +---+ +-- LSP2
+-+-+-+-+-+-+-+ | E | | B | +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | E | | B | +-+-+-+-+-+-+-+
|I|I|I|I|S|I| +---+ +---+ |B|C|D|E|F|A|B| |I|I|I|I|S|I| +---+ +---+ |B|C|D|E|F|A|B|
+-+-+-+-+-+-+ #\* */# +-+-+-+-+-+-+-+ +-+-+-+-+-+-+ #\* */# +-+-+-+-+-+-+-+
#\* [RcW_D(E)] [RcW_D(C)] */# |I|S|I|I|I|I| #\* [RcW_D(E)] [RcW_D(C)] */# |I|S|I|I|I|I|
[RaP_D(D)] #\* */# +-+-+-+-+-+-+ [RaP_D(D)] #\* */# +-+-+-+-+-+-+
#\* */# [RaP_D(B)] #\* */# [RaP_D(B)]
+-+-+-+-+-+-+-+ +---+ [RcW_D(D)] +---+ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ [RcW_D(D)] +---+ +-+-+-+-+-+-+-+
|D|E|F|A|B|C|D| +-- | D | xxxxxxxxxxxxxxxxx | C | |C|D|E|F|A|B|C| |D|E|F|A|B|C|D| +-- | D | xxxxxxxxxxxxxxxxx | C | |C|D|E|F|A|B|C|
+-+-+-+-+-+-+-+ LSP 1 +---+ [RaP_D(C)] +---+ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ LSP1 +---+ [RaP_D(C)] +---+ +-+-+-+-+-+-+-+
|I|I|I|I|I|S| LSP 2 |S|I|I|I|I|I| |I|I|I|I|I|S| LSP2 |S|I|I|I|I|I|
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
----- physical links ***** RcW_D ##### RaP_D ----- physical links ***** RcW_D ##### RaP_D
I: Intact S: Severed I: Intact S: Severed
Figure 8. Steering operation and protection switching Figure 9. Steering operation and protection switching
As shown in Figure 8, LSP1 enters the ring from Node A while LSP2 As shown in Figure 9, LSP1 enters the ring from Node A while LSP2
enters the ring from Node B, and both of them have the same enters the ring from Node B, and both of them have the same
destination node D. destination node D.
In the normal state, LSP 1 is carried by the clockwise working ring In the normal state, LSP1 is carried by the clockwise working ring
tunnel (RcW_D) through the path A->B->C->D, the label operation is: tunnel (RcW_D) through the path A->B->C->D, the label operation is:
[LSP1] -> [RcW_D(B)|LSP1](NodeA) -> [RcW_D(C)| LSP1](NodeB) -> [LSP1] -> [RcW_D(B)|LSP1](NodeA) -> [RcW_D(C)| LSP1](NodeB) ->
[RcW_D(D)|LSP1](NodeC) -> [LSP1] (data traffic carried by LSP 1) . [RcW_D(D)|LSP1](NodeC) -> [LSP1] (data traffic carried by LSP1) .
LSP2 is carried by the clockwise working ring tunnel (RcW_D) throught LSP2 is carried by the clockwise working ring tunnel (RcW_D) throught
the path B->C->D, the label operation is: [LSP2] -> the path B->C->D, the label operation is: [LSP2] ->
[RcW_D(C)|LSP2](NodeB) -> [RcW_D(D)|LSP2](NodeC) -> [LSP2] (data [RcW_D(C)|LSP2](NodeB) -> [RcW_D(D)|LSP2](NodeC) -> [LSP2] (data
traffic carried by LSP 1) . traffic carried by LSP2) .
If the link between nodes C and D fails, according to the fault If the link between nodes C and D fails, according to the fault
detection and distribution mechanisms, Node D will find out that detection and distribution mechanisms, Node D will find out that
there is a failure in the link between C and D, and it will update there is a failure in the link between C and D, and it will update
the link state of its ring topology, changing the link between C and the link state of its ring topology, changing the link between C and
D from normal to fault. In the direction that opposite to the D from normal to fault. In the direction that opposite to the
failure position, Node D will send the state report message to Node failure position, Node D will send the state report message to Node
E, informing Node E of the fault between C and D, and E will update E, informing Node E of the fault between C and D, and E will update
the link state of its ring topology accordingly, changing the link the link state of its ring topology accordingly, changing the link
between C and D from normal to fault. In this way, the state report between C and D from normal to fault. In this way, the state report
message is sent hop by hop in the clockwise direction. Similar to message is sent hop by hop in the clockwise direction. Similar to
Node D, Node C will send the failure information in the anti- Node D, Node C will send the failure information in the anti-
clockwise direction. clockwise direction.
When Node A receives the failure report message and updates the link When Node A receives the failure report message and updates the link
state of its ring topology, it is aware that there is a fault on the state of its ring topology, it is aware that there is a fault on the
clockwise working ring tunnel to node D (RcW_D), and LSP 1 enters the clockwise working ring tunnel to node D (RcW_D), and LSP1 enters the
ring locally and is carried by this ring tunnel, thus Node A will ring locally and is carried by this ring tunnel, thus Node A will
decide to switch the LSP1 onto the anticlockwise protection ring decide to switch the LSP1 onto the anticlockwise protection ring
tunnel to node D (RaP_D). After the switchover, LSP1 will follow the tunnel to node D (RaP_D). After the switchover, LSP1 will follow the
path A->F->E->D, the label operation is: [LSP1] -> [RaP_D(F)| path A->F->E->D, the label operation is: [LSP1] -> [RaP_D(F)|
LSP1](NodeA) -> [RaP_D(E)|LSP1](NodeF) -> [RaP_D(D)|LSP1](NodeE) -> LSP1](NodeA) -> [RaP_D(E)|LSP1](NodeF) -> [RaP_D(D)|LSP1](NodeE) ->
[LSP1] (data traffic carried by LSP 1). [LSP1] (data traffic carried by LSP1).
The same also apply to the operation of LSP2. When Node B updates The same also apply to the operation of LSP2. When Node B updates
the link state of its ring topology, and finds out that the working the link state of its ring topology, and finds out that the working
ring tunnel RcW_D has failed, it will switch the LSP2 to the ring tunnel RcW_D has failed, it will switch the LSP2 to the
anticlockwise protection tunnel RaP_D. After the switchover, LSP2 anticlockwise protection tunnel RaP_D. After the switchover, LSP2
goes through the path B->A->F->E->D, and the label operation is: goes through the path B->A->F->E->D, and the label operation is:
[LSP2] -> [RaP_D(A)|LSP2](NodeB) -> [RaP_D(F)|LSP2](NodeA) -> [LSP2] -> [RaP_D(A)|LSP2](NodeB) -> [RaP_D(F)|LSP2](NodeA) ->
[RaP_D(E)|LSP2](NodeF) -> [RaP_D(D)|LSP2](NodeE) -> [LSP2](data [RaP_D(E)|LSP2](NodeF) -> [RaP_D(D)|LSP2](NodeE) -> [LSP2](data
traffic carried by LSP 2). traffic carried by LSP2).
Then assume the link between nodes A and B breaks down, as shown in Then assume the link between nodes A and B breaks down, as shown in
Figure 9. Similar to the above failure case, Node B will detect a Figure 10. Similar to the above failure case, Node B will detect a
fault in the link between A and B, and it will update the link state fault in the link between A and B, and it will update the link state
of its ring topology, changing the link state between A and B from of its ring topology, changing the link state between A and B from
normal to fault. The state report message is sent hop by hop in the normal to fault. The state report message is sent hop by hop in the
clockwise direction, notifying every node that there is a fault clockwise direction, notifying every node that there is a fault
between node A and B, and every node updates the link state of its between node A and B, and every node updates the link state of its
ring topology. As a result, Node A will detect a fault in the ring topology. As a result, Node A will detect a fault in the
working ring tunnel to node D, and switch LSP1 to the protection ring working ring tunnel to node D, and switch LSP1 to the protection ring
tunnel, while Node B determine that the working ring tunnel for LSP2 tunnel, while Node B determine that the working ring tunnel for LSP2
still works fine, and will not perform the switchover. still works fine, and will not perform the switchover.
/-- LSP l /-- LSPl
+-+-+-+-+-+-+-+ +---+ ###[RaP_D(F)]#### +---/ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ ###[RaP_D(F)]#### +---/ +-+-+-+-+-+-+-+
|F|A|B|C|D|E|F| | F | ----------------- | A | |A|B|C|D|E|F|A| |F|A|B|C|D|E|F| | F | ----------------- | A | |A|B|C|D|E|F|A|
+-+-+-+-+-+-+-+ +---+ ***[RcW_D(A)]**** +---+ +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ ***[RcW_D(A)]**** +---+ +-+-+-+-+-+-+-+
|I|S|I|I|I|I| #/* x |S|I|I|I|I|I| |I|S|I|I|I|I| #/* x |S|I|I|I|I|I|
+-+-+-+-+-+-+ #/* x +-+-+-+-+-+-+ +-+-+-+-+-+-+ #/* x +-+-+-+-+-+-+
[RaP_D(E)] #/*[RcW_D(F)] [RcW_D(B)]x [RaP_D(A)] [RaP_D(E)] #/*[RcW_D(F)] [RcW_D(B)]x [RaP_D(A)]
#/* x +-- LSP 2 #/* x +-- LSP2
+-+-+-+-+-+-+-+ +---+ +---++-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ +---++-+-+-+-+-+-+-+
|E|F|A|B|C|D|E| | E | | B ||B|C|D|E|F|A|B| |E|F|A|B|C|D|E| | E | | B ||B|C|D|E|F|A|B|
+-+-+-+-+-+-+-+ +---+ +---++-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +---+ +---++-+-+-+-+-+-+-+
|I|I|S|I|I|I| #\* */# |I|I|I|I|I|S| |I|I|S|I|I|I| #\* */# |I|I|I|I|I|S|
+-+-+-+-+-+-+ #\*[RcW_D(E)] [RcW_D(C)] */# +-+-+-+-+-+-+ +-+-+-+-+-+-+ #\*[RcW_D(E)] [RcW_D(C)] */# +-+-+-+-+-+-+
[RaP_D(D)] #\* */# [RaP_D(B)] [RaP_D(D)] #\* */# [RaP_D(B)]
+-+-+-+-+-+-+-+ #\* */# +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ #\* */# +-+-+-+-+-+-+-+
|D|E|F|A|B|C|D| +---+ ***[RcW_D(D)]*** +---+ |C|D|E|F|A|B|C| |D|E|F|A|B|C|D| +---+ ***[RcW_D(D)]*** +---+ |C|D|E|F|A|B|C|
+-+-+-+-+-+-+-+ +-- | D | ---------------- | C | +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ +-- | D | ---------------- | C | +-+-+-+-+-+-+-+
|I|I|I|S|I|I| LSP1 +---+ ###[RaP_D(C)]### +---+ |I|I|I|I|S|I| |I|I|I|S|I|I| LSP1 +---+ ###[RaP_D(C)]### +---+ |I|I|I|I|S|I|
+-+-+-+-+-+-+ LSP2 +-+-+-+-+-+-+ +-+-+-+-+-+-+ LSP2 +-+-+-+-+-+-+
----- physical links ***** RcW_D ##### RaP_D ----- physical links ***** RcW_D ##### RaP_D
Figure 9. Steering operation and protection switching (2) Figure 10. Steering operation and protection switching (2)
4.4. Interconnected Ring Protection 4.4. Interconnected Ring Protection
4.4.1. Interconnected Ring Topology 4.4.1. Interconnected Ring Topology
Interconnected ring topology is often used in MPLS-TP networks. This Interconnected ring topology is often used in MPLS-TP networks. This
document will discuss two typical interconnected ring topologies: document will discuss two typical interconnected ring topologies:
1. Single-node interconnected rings 1. Single-node interconnected rings
skipping to change at page 17, line 5 skipping to change at page 18, line 5
rings. Node C is the interconnection node between Ring1 and rings. Node C is the interconnection node between Ring1 and
Ring2. Ring2.
2. Dual-node interconnected rings 2. Dual-node interconnected rings
In dual-node interconnected rings, the connection between the In dual-node interconnected rings, the connection between the
two rings is through two nodes. The two interconnection nodes two rings is through two nodes. The two interconnection nodes
belong to both interconnected rings. This topology can belong to both interconnected rings. This topology can
recover from one interconnection node failure. recover from one interconnection node failure.
Figure 10 shows the topology of single-node interconnected rings. Figure 11 shows the topology of single-node interconnected rings.
Node C is the interconnection node between Ring1 and Ring2. Node C is the interconnection node between Ring1 and Ring2.
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| A |------| B |----- -----| G |------| H | | A |------| B |----- -----| G |------| H |
+---+ +---+ \ / +---+ +---+ +---+ +---+ \ / +---+ +---+
| \ / | | \ / |
| \ +---+ / | | \ +---+ / |
| Ring1 | C | Ring2 | | Ring1 | C | Ring2 |
| / +---+ \ | | / +---+ \ |
| / \ | | / \ |
+---+ +---+ / \ +---+ +---+ +---+ +---+ / \ +---+ +---+
| F |------| E |----- -----| J |------| I | | F |------| E |----- -----| J |------| I |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Figure 10. Single-node interconnected rings Figure 11. Single-node interconnected rings
Figure 11 shows the topology of dual-node interconnected rings. Figure 12 shows the topology of dual-node interconnected rings.
Nodes C and Node D are the interconnection nodes between Ring1 and Nodes C and Node D are the interconnection nodes between Ring1 and
Ring2. Ring2.
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| A |------| B |------| C |------| G |------| H | | A |------| B |------| C |------| G |------| H |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| | | | | | | |
| | | | | | | |
| Ring1 | | Ring2 | | Ring1 | | Ring2 |
| | | | | | | |
| | | | | | | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| F |------| E |------| D |------| J |------| I | | F |------| E |------| D |------| J |------| I |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Figure 11. Dual-node interconnected rings Figure 12. Dual-node interconnected rings
4.4.2. Interconnected Ring Protection Mechanisms 4.4.2. Interconnected Ring Protection Mechanisms
Interconnected rings can be regarded as two independent rings. Ring Interconnected rings can be treated as two independent rings. Ring
protection switching protocol operates on each ring independently. protection switching (RPS) protocol operates on each ring
Failure in one ring only triggers protection switching on the ring independently. Failure in one ring only triggers protection
itself and does not affect the other ring. Protection switching in a switching on the ring itself and does not affect the other ring.
single ring is same as the one described in section 4.3. This way, protection switching on each ring is the same as the
mechanisms described in section 4.3.
The service LSPs that traverse the interconnected rings via the The service LSPs that traverse the interconnected rings via the
interconnection nodes MUST use different ring tunnels in different interconnection nodes MUST use different ring tunnels in different
rings. On the interconnection node, the ring tunnel label used in rings, and the service LSPs traversing the interconnected rings are
the source ring will be popped, and the ring tunnel label of stitched by the interconnection node. On the interconnection node,
destination ring will be pushed the ring tunnel label used in the source ring will be popped, the
For the protected interconnection node in dual-node interconnected service LSP label will be swapped, and the ring tunnel label of the
ring, the service LSPs in the interconnection nodes should use the destination ring will be pushed.
same LSP label. So any interconnection node can terminate a source
ring runnel and push a destination ring tunnel according to the
service LSP label.
Two interconnection nodes can be managed as a virtual interconnection In the dual-node interconnected ring scenario, the two
node group. Each ring should assign ring tunnels to the virtual interconnection nodes can be managed as a virtual interconnection
interconnection node group. The interconnection nodes in the group node group. Each ring should assign working and protection ring
should terminate the working ring tunnel in each ring. The tunnels for the virtual interconnection node group. Both the
protection ring tunnel is an open ring to switch with the working interconnection nodes in the virtual interconnection node group can
ring tunnel at the nodes that detect the fault and ends at the egress terminate the working ring tunnel of each ring. The protection ring
node. tunnel is used to protect the working ring tunnel of each ring and
can be terminated by any node in the virtual interconnection node
group.
On the nodes in the virtual interconnection node group of the dual-
node interconnected ring, the same label is allocated for each
service LSP. This way any interconnection node in the virtual node
group can stitch the service LSPs between the source ring tunnel and
the destination ring tunnel.
When the service traffic passes through the interconnection node, the When the service traffic passes through the interconnection node, the
direction of the working ring tunnels in each ring for this service direction of the working ring tunnels in each ring for this service
traffic should be the same. For example, if the working ring tunnel traffic should be the same. For example, if the working ring tunnel
follows the clockwise direction in Ring1, the working ring tunnel for follows the clockwise direction in Ring1, the working ring tunnel for
the same service traffic in Ring2 also follows the clockwise the same service traffic in Ring2 SHOULD also follow the clockwise
direction when the service leaves Ring1 and enters Ring2. direction when the service leaves Ring1 and enters Ring2.
4.4.3. Ring Tunnels in Interconnected Rings 4.4.3. Ring Tunnels in Interconnected Rings
The same ring tunnels as described in section 4.1 are used in each The same ring tunnels as described in section 4.1 are used in each
ring of the interconnected rings. Note that ring tunnels to the ring of the interconnected rings. Note that ring tunnels to the
virtual interconnection node group will be established by each ring virtual interconnection node group will be established by each ring
of the interconnected rings, i.e.: of the interconnected rings, i.e.:
o one clockwise working ring tunnel to the virtual interconnection o one clockwise working ring tunnel to the virtual interconnection
skipping to change at page 19, line 15 skipping to change at page 20, line 21
o To Node C: R1cW_C, R1aW_C, R1cP_C, R1aP_C o To Node C: R1cW_C, R1aW_C, R1cP_C, R1aP_C
o To Node D: R1cW_D, R1aW_D, R1cP_D, R1aP_D o To Node D: R1cW_D, R1aW_D, R1cP_D, R1aP_D
o To Node E: R1cW_E, R1aW_E, R1cP_E, R1aP_E o To Node E: R1cW_E, R1aW_E, R1cP_E, R1aP_E
o To Node F: R1cW_F, R1aW_F, R1cP_F, R1aP_F o To Node F: R1cW_F, R1aW_F, R1cP_F, R1aP_F
o To the virtual interconnection node group (including Node F and o To the virtual interconnection node group (including Node F and
Node A): R1cW_F&A, R1aW_F&A, R1cP_F&A, R1aP_F&A; Node A): R1cW_F&A, R1aW_F&A, R1cP_F&A, R1aP_F&A
All the ring tunnels established in Ring2 in Figure 12 are All the ring tunnels established in Ring2 in Figure 13 are
provisioned as follows: provisioned as follows:
o To Node A: R2cW_A, R2aW_A, R2cP_A, R2aP_A o To Node A: R2cW_A, R2aW_A, R2cP_A, R2aP_A
o To Node F: R2cW_F, R2aW_F, R2cP_F, R2aP_F o To Node F: R2cW_F, R2aW_F, R2cP_F, R2aP_F
o To Node G: R2cW_G, R2aW_G, R2cP_G, R2aP_G o To Node G: R2cW_G, R2aW_G, R2cP_G, R2aP_G
o To Node H: R2cW_H, R2aW_H, R2cP_H, R2aP_H o To Node H: R2cW_H, R2aW_H, R2cP_H, R2aP_H
skipping to change at page 20, line 36 skipping to change at page 21, line 36
c\a a/c c\a a/c
c\a a/c c\a a/c
+---+aaaaaaaaaaaa +---+ +---+aaaaaaaaaaaa +---+
LSP1--->| D |-------------| C | LSP1--->| D |-------------| C |
+---+ccccccccccccc+---+ +---+ccccccccccccc+---+
ccccccccccc R1cW_F&A ccccccccccc R1cW_F&A
aaaaaaaaaaa R1aP_F&A aaaaaaaaaaa R1aP_F&A
ccccccccccc R2cW_I ccccccccccc R2cW_I
aaaaaaaaaaa R2aP_I aaaaaaaaaaa R2aP_I
Figure 12. Ring tunnels for the interconnected rings Figure 13. Ring tunnels for the interconnected rings
4.4.4. Interconnected Ring Switching Procedure 4.4.4. Interconnected Ring Switching Procedure
As shown in Figure 12, for the service traffic LSP1 which enters As shown in Figure 13, for the service traffic LSP1 which enters
Ring1 at Node D and exits Ring1 at Node F and continues to enter Ring1 at Node D and leaves Ring1 at Node F and continues to enter
Ring2 at Node F and exits Ring2 at Node I, the protection scheme is Ring2 at Node F and leaves Ring2 at Node I, the protection scheme is
described below. described as below.
In normal state, LSP1 follows R1cW_F&A in Ring1 and R2CW_I in Ring2. In normal state, LSP1 follows R1cW_F&A in Ring1 and R2CW_I in Ring2.
The label used for the working ring tunnel R1cW_F&A in Ring1 is The label used for the working ring tunnel R1cW_F&A in Ring1 is
popped and the label used for the working ring tunnel R2cW_I will be popped and the label used for the working ring tunnel R2cW_I will be
pushed based the inner label lookup at the interconnection node F. pushed based the inner label lookup at the interconnection node F.
The working path that the service traffic LSP1 follows is: The working path that the service traffic LSP1 follows is:
LSP1->R1cW_F&A (D->E->F)->R2cW_I(F->G->H->I)->LSP1. LSP1->R1cW_F&A (D->E->F)->R2cW_I(F->G->H->I)->LSP1.
In case of link failure, for example, when a failure occurs on the In case of link failure, for example, when a failure occurs on the
link between Node F and Node E, Nodes F and E will detect the failure link between Node F and Node E, Nodes F and E will detect the failure
and execute protection switching as described in 2.2.1.1. The path and execute protection switching as described in 4.3.1.1. The path
that the service traffic LSP1 follows after switching change to that the service traffic LSP1 follows after switching change to
LSP1->R1cW_F&A(D->E)->R1aP_F&A(E->D->C->B->A->F)->R1cW_F(F) LSP1->R1cW_F&A(D->E)->R1aP_F&A(E->D->C->B->A->F)->R1cW_F(F)
->R2cW_I(F->G->H->I)->LSP1. ->R2cW_I(F->G->H->I)->LSP1.
In case of a non interconnection node failure, for example, when the In case of a non interconnection node failure, for example, when the
failure occurs at Node E in Ring1, Nodes F and D will detect the failure occurs at Node E in Ring1, Nodes F and D will detect the
failure and execute protection switching as described in 2.2.1.2. failure and execute protection switching as described in 4.3.1.2.
The path that the service traffic LSP1 follows after switching The path that the service traffic LSP1 follows after switching
becomes: LSP1->R1cW_F&A(D)->R1aP_F&A(D->C->B->A->F)-> becomes: LSP1->R1cW_F&A(D)->R1aP_F&A(D->C->B->A->F)->
R1cW_F(F)->R2cW_I(F->G->H->I). R1cW_F(F)->R2cW_I(F->G->H->I).
In case of an interconnection node failure, for example, when the In case of an interconnection node failure, for example, when the
failure occurs at the interconnection Node F. Nodes E and A in Ring1 failure occurs at the interconnection Node F. Nodes E and A in Ring1
will detect the failure, and execute protection switching as will detect the failure, and execute protection switching as
described in 2.2.1.2. Nodes G and A in Ring2 will also detects the described in 4.3.1.2. Nodes G and A in Ring2 will also detects the
failure, and execute protection switching. The path that the service failure, and execute protection switching. The path that the service
traffic LSP1 follows after switching is: traffic LSP1 follows after switching is:
LSP1->R1cW_F&A(D->E)->R1aP_F&A(E->D->C->B->A)->R1cW_A(A) LSP1->R1cW_F&A(D->E)->R1aP_F&A(E->D->C->B->A)->R1cW_A(A)
->R2aP_I(A->J->I)->LSP1. ->R2aP_I(A->J->I)->LSP1.
4.4.5. Interconnected Ring Detection Mechanism 4.4.5. Interconnected Ring Detection Mechanism
As show in Figure 13, the service traffic LSP1 traverses A->B-C in As show in Figure 14, the service traffic LSP1 traverses A->B->C in
Ring1 and C->G->H->I in Ring2. Node C and Node D are the Ring1 and C->G->H->I in Ring2. Node C and Node D are the
interconnection nodes. When both the link between Node C and Node G interconnection nodes. When both the link between Node C and Node G
and the link between Node C and Node D fail, the ring tunnel from and the link between Node C and Node D fail, the ring tunnel from
Node C to Node I in Ring 2 becomes unreachable. However, Node D is Node C to Node I in Ring2 becomes unreachable. However, Node D is
still available, and LSP1 can still reach Node I. still available, and LSP1 can still reach Node I.
+---+ *********+---+**********+---+ +---+**********+---+ +---+ *********+---+**********+---+ +---+**********+---+
LSP1->| A |----------| B |----------| C |XXXXXXXXXX| G |----------| H | LSP1->| A |----------| B |----------| C |XXXXXXXXXX| G |----------| H |
+---+##########+---+##########+---+ +---+##########+---+ +---+##########+---+##########+---+ +---+##########+---+
|# X #|* |# X #|*
|# X #|* |# X #|*
|# Ring1 X Ring2 #|* |# Ring1 X Ring2 #|*
|# X #|* |# X #|*
|# X #|* |# X #|*
+---+##########+---+##########+---+######### +---+##########+---+ +---+##########+---+##########+---+######### +---+##########+---+
| F |----------| E |----------| D |----------| J |----------| I | ->LSP1 | F |----------| E |----------| D |----------| J |----------| I | ->LSP1
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
*********** R1cW_C&D *********** R1cW_C&D
########### R1aP_C&D ########### R1aP_C&D
*********** R2cW_I *********** R2cW_I
########### R2aP_I ########### R2aP_I
Figure 13. Interconnected ring Figure 14. Interconnected ring
In order to achieve this, the interconnection nodes need to know the In order to achieve this, the interconnection nodes need to know the
ring topology of each ring so that they can judge whether a node is ring topology of each ring so that they can judge whether a node is
reachable. This judgment is based on the knowledge of each ring reachable. This judgment is based on the knowledge of each ring
topology and the fault location as described in section 3.4. The topology and the fault location as described in section 3.4. The
ring topology can be obtained from the NMS or topology discovery ring topology can be obtained from the NMS or topology discovery
mechanisms. The fault location can be obtained by transmitting the mechanisms. The fault location can be obtained by transmitting the
fault information around the ring. The nodes that detect the failure fault information around the ring. The nodes that detect the failure
will transmit the fault information in the opposite direction node by will transmit the fault information in the opposite direction node by
node in the ring. When the interconnection node receives the message node in the ring. When the interconnection node receives the message
that informs the failure, it will quickly calculate the location of that informs the failure, it will quickly calculate the location of
the fault by the topology information that is maintained by itself the fault by the topology information that is maintained by itself
and determines whether the LSPs entering the ring at itself can reach and determines whether the LSPs entering the ring at itself can reach
the destination. If the destination node is reachable, the LSP will the destination. If the destination node is reachable, the LSP will
exit the source ring and enter the destination ring. If the leave the source ring and enter the destination ring. If the
destination node is not reachable, the LSP will switch to the destination node is not reachable, the LSP will switch to the
anticlockwise protection ring tunnel. anticlockwise protection ring tunnel.
In Figure 13, Node C determines that the ring tunnel to Node I is In Figure 14, Node C determines that the ring tunnel to Node I is
unreachable, the service traffic LSP1 for which the destination node unreachable, the service traffic LSP1 for which the destination node
on the ring tunnel is Node I should switch to the protection LSP on the ring tunnel is Node I should switch to the protection LSP
(R1aP_C&D) and consequently the service traffic LSP1 traverses the (R1aP_C&D) and consequently the service traffic LSP1 traverses the
interconnected rings at Node D. Node D will remove the ring tunnel interconnected rings at Node D. Node D will remove the ring tunnel
label of Ring1 and add the ring tunnel label of Ring2. label of Ring1 and add the ring tunnel label of Ring2.
5. Ring Protection Coordination Protocol 5. Ring Protection Coordination Protocol
5.1. RPS Protocol 5.1. RPS Protocol
The MSRP protection operation MUST be controlled with the help of the The MSRP protection operation MUST be controlled with the help of the
Ring Protection Switch Protocol (RPS). The RPS processes in each of Ring Protection Switch Protocol (RPS). The RPS processes in each of
the individual ring nodes that form the ring SHOULD communicate using the individual ring nodes that form the ring SHOULD communicate using
the G-ACh channel. the G-ACh channel.
The RPS protocol MUST carry the ring status information and RPS The RPS protocol MUST carry the ring status information and RPS
requests, i.e., automatically initiated and externally initiated, requests, i.e., automatically initiated and externally initiated,
between the ring nodes. between the ring nodes.
Each node on the ring MUST be uniquely identified by assigning it a Each node on the ring MUST be uniquely identified by assigning it a
node ID. The maximum number of nodes on the ring supported by the node ID. The node ID MUST be unique on each ring. The maximum
RPS protocol is 127. The node ID SHOULD be independent of the order number of nodes on the ring supported by the RPS protocol is 127.
in which the nodes appear on the ring. The node ID is used to The node ID SHOULD be independent of the order in which the nodes
identity the source and destination nodes of each RPS request. appear on the ring. The node ID is used to identity the source and
destination nodes of each RPS request.
Each node SHOULD have a ring map containing information about the Every node obtains the ring topology either by configuration or via
sequence of the nodes around the ring. The method of configuring the some topology discovery mechanism. The ring map consists of the ring
nodes with the ring maps is out of scope of this document. topology information, and connectivity status (Intact or Severed)
between the adjacent ring nodes, which is determined via the OAM
message exchange between the adjacent nodes. The ring map is used by
every ring node to determine the switchover behavoir of the ring
tunnels.
When no protection switching is active on the ring, each node MUST When no protection switching is active on the ring, each node MUST
dispatch periodically RPS requests to the two adjacent nodes, dispatch periodically RPS requests to the two adjacent nodes,
indicating No Request (NR). When a node determines that a protection indicating No Request (NR). When a node determines that a protection
switching is required, it MUST send the appropriate RPS request in switching is required, it MUST send the appropriate RPS request in
both directions. both directions.
+---+ A->B(NR) +---+ B->C(NR) +---+ C->D(NR) +---+ A->B(NR) +---+ B->C(NR) +---+ C->D(NR)
-------| A |-------------| B |-------------| C |------- -------| A |-------------| B |-------------| C |-------
(NR)F<-A +---+ (NR)A<-B +---+ (NR)B<-C +---+ (NR)F<-A +---+ (NR)A<-B +---+ (NR)B<-C +---+
Figure 14. RPS communication between the ring nodes in case of Figure 15. RPS communication between the ring nodes in case of
no failures in the ring no failures in the ring
A destination node is a node that is adjacent to a node that A destination node is a node that is adjacent to a node that
identified a failed span. When a node that is not the destination identified a failed span. When a node that is not the destination
node receives an RPS request and it has no higher priority local node receives an RPS request and it has no higher priority local
request, it MUST transfer in the same direction the RPS request as request, it MUST transfer in the same direction the RPS request as
received. In this way, the switching nodes can maintain direct RPS received. In this way, the switching nodes can maintain direct RPS
protocol communication in the ring. protocol communication in the ring.
+---+ C->B(SF) +---+ B->C(SF) +---+ C->B(SF) +---+ C->B(SF) +---+ B->C(SF) +---+ C->B(SF)
-------| A |-------------| B |----- X -----| C |------- -------| A |-------------| B |----- X -----| C |-------
(SF)C<-B +---+ (SF)C<-B +---+ (SF)B<-C +---+ (SF)C<-B +---+ (SF)C<-B +---+ (SF)B<-C +---+
Figure 15. RPS communication between the ring nodes in case of Figure 16. RPS communication between the ring nodes in case of
failure between nodes B and C failure between nodes B and C
Note that in the case of a bidirectional failure such as a cable cut, Note that in the case of a bidirectional failure such as a cable cut,
the two adjacent nodes detect the failure and send each other an RPS the two adjacent nodes detect the failure and send each other an RPS
request in opposite directions. request in opposite directions.
o In rings utilizing the wrapping protection. When the destination o In rings utilizing the wrapping protection. When the destination
node receives the RPS request it MUST perform the switch from/to node receives the RPS request it MUST perform the switch from/to
the working ring tunnels to/from the protection ring tunnels if it the working ring tunnels to/from the protection ring tunnels if it
has no higher priority active RPS request. has no higher priority active RPS request.
skipping to change at page 25, line 18 skipping to change at page 26, line 24
the transmitted status occurs. the transmitted status occurs.
The first three RPS protocol messages carrying new RPS request SHOULD The first three RPS protocol messages carrying new RPS request SHOULD
be transmitted as fast as possible. For fast protection switching be transmitted as fast as possible. For fast protection switching
within 50 ms, the interval of the first three RPS protocol messages within 50 ms, the interval of the first three RPS protocol messages
SHOULD be 3.3 ms. The successive RPS requests SHOULD be transmitted SHOULD be 3.3 ms. The successive RPS requests SHOULD be transmitted
with the interval of 5 seconds. with the interval of 5 seconds.
5.1.2. RPS PDU Format 5.1.2. RPS PDU Format
Figure 16 depicts the format of an RPS packet that is sent on the Figure 17 depicts the format of an RPS packet that is sent on the
G-ACh. The Channel Type field is set to indicate that the message is G-ACh. The Channel Type field is set to indicate that the message is
an RPS message. The ACH MUST NOT include the ACH TLV Header an RPS message. The ACH MUST NOT include the ACH TLV Header
[RFC5586] meaning that no ACH TLVs can be included in the message. [RFC5586] meaning that no ACH TLVs can be included in the message.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|0 0 0 0|0 0 0 0 0 0 0 0| RPS Channel Type (TBD) | |0 0 0 1|0 0 0 0|0 0 0 0 0 0 0 0| RPS Channel Type (TBD) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dest Node ID | Src Node ID | Request | Reserved | | Dest Node ID | Src Node ID | Request | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16. G-ACh RPS Packet Format Figure 17. G-ACh RPS Packet Format
The following fields MUST be provided: The following fields MUST be provided:
o Destination Node ID: The destination node ID MUST always be set to o Destination Node ID: The destination node ID MUST always be set to
value of the node ID of the adjacent node. Valid destination node value of the node ID of the adjacent node. The Node ID MUST be
ID values are 1-127. unique on each ring. Valid destination node ID values are 1-127.
o Source node ID: The source node ID MUST always be set to the value o Source node ID: The source node ID MUST always be set to the ID
of the node ID generating the RPS request. Valid source node ID value of the node generating the RPS request. The Node ID MUST be
values are 1-127. unique on each ring. Valid source node ID values are 1-127.
o RPS request code: A code consisting of four bits as specified o RPS request code: A code consisting of eight bits as specified
below: below:
+-------------+-----------------------------+----------+ +------------------+-----------------------------+----------+
| Bits 4-1 | Condition, State | Priority | | Bits | Condition, State | Priority |
| (MSB - LSB) | or external Request | | | (MSB - LSB) | or external Request | |
+-------------------------------------------+----------+ +------------------+-----------------------------+----------+
| 1 1 1 1 | Lockout of Protection (LP) | highest | | 0 0 0 0 1 1 1 1 | Lockout of Protection (LP) | highest |
| 1 1 0 1 | Forced Switch (FS) | | | 0 0 0 0 1 1 0 1 | Forced Switch (FS) | |
| 1 0 1 1 | Signal Fail (SF) | | | 0 0 0 0 1 0 1 1 | Signal Fail (SF) | |
| 0 1 1 0 | Manual Switch (MS) | | | 0 0 0 0 0 1 1 0 | Manual Switch (MS) | |
| 0 1 0 1 | Wait-To-Restore (WTR) | | | 0 0 0 0 0 1 0 1 | Wait-To-Restore (WTR) | |
| 0 0 1 1 | Exercise (EXER) | | | 0 0 0 0 0 0 1 1 | Exercise (EXER) | |
| 0 0 0 1 | Reverse Request (RR) | | | 0 0 0 0 0 0 0 1 | Reverse Request (RR) | |
| 0 0 0 0 | No Request (NR) | lowest | | 0 0 0 0 0 0 0 0 | No Request (NR) | lowest |
+-------------+-----------------------------+----------+ +------------------+-----------------------------+----------+
5.1.3. Ring Node RPS States 5.1.3. Ring Node RPS States
Idle state: A node is in the idle state when it has no RPS request Idle state: A node is in the idle state when it has no RPS request
and is sourcing and receiving NR code to/from both directions. and is sourcing and receiving NR code to/from both directions.
Switching state: A node not in the idle or pass-through states is in Switching state: A node not in the idle or pass-through states is in
the switching state. the switching state.
Pass-through state: A node is in the pass-through state when its Pass-through state: A node is in the pass-through state when its
skipping to change at page 41, line 37 skipping to change at page 42, line 37
to have a MEP on the section to its adjacent nodes respectively. In to have a MEP on the section to its adjacent nodes respectively. In
this way, every ring-node only needs to be configured with 2 MEPs. this way, every ring-node only needs to be configured with 2 MEPs.
As shown in the above example, RPS is designed for ring topologies As shown in the above example, RPS is designed for ring topologies
and can achieve ring protection efficiently with minimum protection and can achieve ring protection efficiently with minimum protection
instances and OAM entities, which meets the requirements on topology instances and OAM entities, which meets the requirements on topology
specific recovery mechanisms as specified in [RFC5654]. specific recovery mechanisms as specified in [RFC5654].
6. IANA Considerations 6. IANA Considerations
The Channel Types for the Generic Associated Channel are allocated IANA is requested to administer the assignment of new values defined
from the IANA PW Associated Channel Type registry defined in in this document and summarized in this section.
[RFC4446] and updated by [RFC5586].
IANA is requested to allocate a further Channel Type as follows: 6.1. G-ACh Channel Type
o TBA Ring Protection Switching (RPS) The Channel Types for the Generic Associated Channel (GACH) are
allocated from the IANA PW Associated Channel Type registry defined
in [RFC4446] and updated by [RFC5586].
Note to RFC Editor: this section may be removed on publication as an IANA is requested to allocate a new GACH Channel Type as follows:
RFC.
Value Description Reference
------ -------------------------- ---------------
TBD Ring Protection Switching this document
Protocol (RPS)
6.2. RSP Request Codes
IANA is requested to create a new sub-registry under the
"Multiprotocol Label Switching (MPLS) Operations, Administration, and
Management (OAM) Parameters" registry called the "MPLS RPS Request
Code Registry". All code points within this registry shall be
allocated according to the "Standards Action" procedure as specified
in [RFC5226].
The RPS Request Field is 8 bits, the allocated values are as follows:
Value Description Reference
------- --------------------------- ---------------
0 No Request (NR) this document
1 Reverse Request (RR) this document
2 not assigned
3 Exercise (EXER) this document
4 not assigned
5 Wait-To-Restore (WTR) this document
6 Manual Switch (MS) this document
7-10 not assigned
11 Signal Fail (SF) this document
12 not assigned
13 Forced Switch (FS) this document
14 not assigned
15 Lockout of Protection (LP) this document
16-255 not assigned
7. Security Considerations 7. Security Considerations
This document does not by itself raise any particular security The RPS protocol defined in this document is carried in the G-ACh
considerations. [RFC5586], which is a generalization of the Associated Channel
defined in [RFC4385]. The security considerations specified in these
documents apply to the proposed RPS mechanism.
8. Contributing Authors 8. Contributing Authors
Wen Ye, Minxue Wang, Sheng Liu (China Mobile) Wen Ye, Minxue Wang, Sheng Liu (China Mobile)
Guanghui Sun (Huawei) Guanghui Sun (Huawei)
9. References 9. Acknowledgements
9.1. Normative References The authors would like to thank Gregory Mirsky, Yimin Shen, Eric
Osborne and Spencer Jackson for their valuable comments and
suggestions.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001. Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <http://www.rfc-editor.org/info/rfc4385>.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", BCP 116, RFC 4446, April 2006. Emulation (PWE3)", BCP 116, RFC 4446,
DOI 10.17487/RFC4446, April 2006,
<http://www.rfc-editor.org/info/rfc4446>.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
Associated Channel", RFC 5586, June 2009. "MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<http://www.rfc-editor.org/info/rfc5586>.
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., [RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
and S. Ueno, "Requirements of an MPLS Transport Profile", Sprecher, N., and S. Ueno, "Requirements of an MPLS
RFC 5654, September 2009. Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <http://www.rfc-editor.org/info/rfc5654>.
[RFC6371] Busi, I. and D. Allan, "Operations, Administration, and [RFC6371] Busi, I., Ed. and D. Allan, Ed., "Operations,
Maintenance Framework for MPLS-Based Transport Networks", Administration, and Maintenance Framework for MPLS-Based
RFC 6371, September 2011. Transport Networks", RFC 6371, DOI 10.17487/RFC6371,
September 2011, <http://www.rfc-editor.org/info/rfc6371>.
9.2. Informative References 10.2. Informative References
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear IANA Considerations Section in RFCs", BCP 26, RFC 5226,
Protection", RFC 6378, October 2011. DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
October 2011, <http://www.rfc-editor.org/info/rfc6378>.
[RFC6974] Weingarten, Y., Bryant, S., Ceccarelli, D., Caviglia, D., [RFC6974] Weingarten, Y., Bryant, S., Ceccarelli, D., Caviglia, D.,
Fondelli, F., Corsi, M., Wu, B., and X. Dai, Fondelli, F., Corsi, M., Wu, B., and X. Dai,
"Applicability of MPLS Transport Profile for Ring "Applicability of MPLS Transport Profile for Ring
Topologies", RFC 6974, July 2013. Topologies", RFC 6974, DOI 10.17487/RFC6974, July 2013,
<http://www.rfc-editor.org/info/rfc6974>.
Authors' Addresses Authors' Addresses
Weiqiang Cheng Weiqiang Cheng
China Mobile China Mobile
Email: chengweiqiang@chinamobile.com Email: chengweiqiang@chinamobile.com
Lei Wang Lei Wang
China Mobile China Mobile
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