draft-ietf-mpls-ldp-rmr-extensions-00.txt   draft-ietf-mpls-ldp-rmr-extensions-01.txt 
INTERNET-DRAFT Santosh Esale INTERNET-DRAFT Santosh Esale
Intended Status: Proposed Standard Kireeti Kompella Intended Status: Proposed Standard Kireeti Kompella
Expires: February 9, 2019 Juniper Networks Expires: May 8, 2019 Juniper Networks
August 8, 2018 November 4, 2018
LDP Extensions for RMR LDP Extensions for RMR
draft-ietf-mpls-ldp-rmr-extensions-00 draft-ietf-mpls-ldp-rmr-extensions-01
Abstract Abstract
This document describes LDP extensions to signal Resilient MPLS Ring This document describes LDP extensions to signal Resilient MPLS Ring
(RMR) Label Switched Paths (LSPs). An RMR LSP is a multipoint to (RMR) Label Switched Paths (LSPs). An RMR LSP is a multipoint to
point LSP signaled using LDP (Label Distribution Protocol). RMR point LSP signaled using LDP (Label Distribution Protocol). RMR
Architecture document - draft-ietf-mpls-rmr-02 - describes why and Architecture document - draft-ietf-mpls-rmr-02 - describes why and
how MPLS should be used in ring topologies. how MPLS should be used in ring topologies.
Status of this Memo Status of this Memo
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Mapping message. The use of the interface label space is outside Mapping message. The use of the interface label space is outside
the scope of this document. the scope of this document.
3. RMR Label Withdraw <P, R, C, L> or <P, R, A, L>: a Label Withdraw 3. RMR Label Withdraw <P, R, C, L> or <P, R, A, L>: a Label Withdraw
message with a FEC TLV with a single RMR FEC Element <P, R, C> or message with a FEC TLV with a single RMR FEC Element <P, R, C> or
<P, R, A> and Label TLV with label L. <P, R, A> and Label TLV with label L.
4. RMR LSP <P, R, C> or <P, R, A>: A RMR LSP with egress prefix P, 4. RMR LSP <P, R, C> or <P, R, A>: A RMR LSP with egress prefix P,
Ring ID R and clockwise direction C or anti-clockwise direction A. Ring ID R and clockwise direction C or anti-clockwise direction A.
4.2.2 Preliminary 4.2.2 Preliminary
A node X wishing to participate in LDP RMR signaling SHOULD negotiate A node X wishing to participate in LDP RMR signaling MUST negotiate
the RMR capability with all its neighbors. When the IGP informs X of the RMR capability with all its neighbors. When the IGP informs X of
its RMR neighbors A and C for RID R, it MUST check that A and C have its RMR neighbors A and C for RID R, it MUST check that A and C have
also negotiated the RMR capability with X. If these conditions are also negotiated the RMR capability with X. If these conditions are
not satisfied, X cannot participate in signaling for ring R. This not satisfied, X cannot participate in signaling for ring R. This
applies for all roles that X may play: ingress, transit and egress. applies for all roles that X may play: ingress, transit and egress.
4.2.3 Egress LSR 4.2.3 Egress LSR
Every ring node initiates two counter-rotating LSPs that egress on Every ring node initiates two counter-rotating LSPs that egress on
that node. After the IGP discovers the ring, LDP constructs the that node. After the IGP discovers the ring, LDP constructs the
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to anti-clockwise neighbor. Similarly, LDP constructs a anti- to anti-clockwise neighbor. Similarly, LDP constructs a anti-
clockwise RMR FEC <P, R, A> and sends it in a Label Mapping message clockwise RMR FEC <P, R, A> and sends it in a Label Mapping message
to clockwise neighbor. This SHOULD establish a clockwise and anti- to clockwise neighbor. This SHOULD establish a clockwise and anti-
clockwise LSP - in terms of data traffic - in the clockwise and anti- clockwise LSP - in terms of data traffic - in the clockwise and anti-
clockwise direction respectively. clockwise direction respectively.
Furthermore, if a label other than implicit or explicit null is Furthermore, if a label other than implicit or explicit null is
advertised for a LSP, LDP SHOULD add a pop route for this label in advertised for a LSP, LDP SHOULD add a pop route for this label in
the Incoming Label Map (ILM) MPLS table. the Incoming Label Map (ILM) MPLS table.
When the node is no longer part of the ring, it SHOULD tear down its When the node is no longer part of the ring, it MUST tear down its
egress LSPs - CW and AC - by sending a label withdraw message. egress LSPs - CW and AC - by sending a label withdraw message.
4.2.4 Ingress and Transit LSR 4.2.4 Ingress and Transit LSR
When a transit LSR R5 depicted in figure 1 receives a label map When a transit LSR R5 depicted in figure 1 receives a label map
message with RMR FEC Element <R0, 17, A, L1> from a downstream LDP message with RMR FEC Element <R0, 17, A, L1> from a downstream LDP
session to R4, it SHOULD verify that R4 is indeed its anticlockwise session to R4, it SHOULD verify that R4 is indeed its anticlockwise
neighbor for ring 17. If not, it SHOULD stop decoding the FEC TLV, neighbor for ring 17. If not, it SHOULD stop decoding the FEC TLV,
abort processing the message containing the TLV, send an "Unknown abort processing the message containing the TLV, send an "Unknown
FEC" Notification message to its LDP peer R4 signaling an error and FEC" Notification message to its LDP peer R4 signaling an error and
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sending the traffic back where it came from, but with a different sending the traffic back where it came from, but with a different
label. The protection path for the CW LSP is to swap L3 with L2 with label. The protection path for the CW LSP is to swap L3 with L2 with
next hop R4. next hop R4.
5. LSP Hierarchy 5. LSP Hierarchy
R9 R10 R11 R9 R10 R11
. . . . . .
. . . . . . . .
. . . .
R8 . . . R9 R8 . . . R12
. . . .
. . . .
. . . .
R0 . . . R1 R0 . . . R1
. . . .
R7 R2 R7 R2
Anti- | . Ring . | Anti- | . Ring . |
Clockwise | . . | Clockwise Clockwise | . . | Clockwise
v . RID = 17 . v v . RID = 17 . v
R6 R3 R6 R3
. . . .
R5 . . . R4 R5 . . . R4
Figure 3: Ring 17 with rest of the Network Figure 3: Ring 17 with rest of the Network
Suppose R5 needs to reach R10. Only RMR LSPs are setup inside the Suppose R5 needs to reach R10. Only RMR LSPs are setup inside the
ring 17. Additionally, whenever services on R5 need to reach R10, R5 ring 17. Additionally, whenever services on R5 need to reach R10, R5
 End of changes. 6 change blocks. 
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