Internet DRAFT - draft-kompella-isis-ospf-rmr
draft-kompella-isis-ospf-rmr
IS-IS OSPF K. Kompella
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track October 30, 2016
Expires: May 3, 2017
IGP Extensions for Resilient MPLS Rings
draft-kompella-isis-ospf-rmr-00
Abstract
This document describes the use of IS-IS and OSPF for discovering
Resilient MPLS Rings (RMR). RMR relies on the IGP for discovery of
the ring elements and properties, as well as subsequent changes to
the ring topology. Details of auto-discovery and operation are given
in the RMR architecture document; this document simply describes the
formats of RMR-related constructs in IS-IS and OSPF.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on May 3, 2017.
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Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 2
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
2.1. Provisioning . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Announcement . . . . . . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Rings are a very common topology in transport networks. A ring is
the simplest topology offering link and node resilience. Rings are
nearly ubiquitous in access and aggregation networks. As MPLS
increases its presence in such networks, and takes on a greater role
in transport, it is imperative that MPLS handles rings well; this is
not the case today. The RMR architecture document
[I-D.ietf-mpls-rmr] describes the motivations and operation of RMR.
RMR uses protocols such as IS-IS [RFC5305] and OSPF[RFC3630] for
auto-discovery, and RSVP-TE [RFC3209] and LDP [RFC5036] for signaling
LSPs. This document gives the specifics of Type-Length-Value (TLV)
formats for IS-IS and OSPF.
1.1. Definitions
For a more detailed description, see [I-D.ietf-mpls-rmr].
A ring is a subgraph of a given graph G = (V, E), consisting of a
subset of n nodes {R_i, 0 <= i < n}. The directed edges {(R_i,
R_i+1) and (R_i+1, R_i), 0 <= i < n-1} must be a subset of E (note
that index arithmetic is done modulo n). We define the direction
from node R_i to R_i+1 as "clockwise" (CW) and the reverse direction
as "anticlockwise" (AC). As there may be several rings in a graph,
we number each ring with a distinct ring ID RID.
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R0 . . . R1
. .
R7 R2
Anti- | . Ring . |
Clockwise | . . | Clockwise
v . RID = 17 . v
R6 R3
. .
R5 . . . R4
Figure 1: Ring with 8 nodes
The following terminology is used for ring LSPs:
Ring ID (RID): A non-zero number that identifies a ring; this is
unique in some scope of a Service Provider's network. A node may
belong to multiple rings.
Ring node: A member of a ring. Note that a device may belong to
several rings.
Node index: A logical numbering of nodes in a ring, from zero upto
one less than the ring size. Used purely for exposition in this
document.
Ring master: The ring master initiates the ring identification
process. Mastership is indicated in the IGP by a two-bit field.
Ring neighbors: Nodes whose indices differ by one (modulo ring
size).
Ring links: Links that connnect ring neighbors.
Express links: Links that connnect non-neighboring ring nodes.
Ring direction: A two-bit field in the IGP indicating the direction
of a link. The choices are:
UN: 00 undefined link
CW: 01 clockwise ring link
AC: 10 anticlockwise ring link
EX: 11 express link
Ring Identification: The process of discovering ring nodes, ring
links, link directions, and express links.
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The following notation is used for ring LSPs:
R_k: A ring node with index k. R_k has AC neighbor R_(k-1) and CW
neighbor R_(k+1).
RL_k: A (unicast) Ring LSP anchored on node R_k.
CL_jk: A label allocated by R_j for RL_k in the CW direction.
AL_jk: A label allocated by R_j for RL_k in the AC direction.
P_jk (Q_jk): A Path (Resv) message sent by R_j for RL_k.
2. Theory of Operation
Say a ring has ring ID RID. The ring is provisioned by choosing one
or more ring masters for the ring and assigning them the RID. Other
nodes in the ring may also be assigned this RID, or may be configured
as "promiscuous". Ring discovery then kicks in. When each ring node
knows its CW and AC ring neighbors and its ring links, and all
express links have been identified, ring identification is complete.
Once ring identification is complete, each node signals one or more
ring LSPs RL_i. RL_i, anchored on node R_i, consists of two counter-
rotating unicast LSPs that start and end at R_i. A ring LSP is
"multipoint": any node R_j can use RL_i to send traffic to R_i; this
can be in either the CW or AC directions, or both (i.e., load
balanced). Both of these counter-rotating LSPs are "active"; the
choice of direction to send traffic to R_i is determined by policy at
the node where traffic is injected into the ring. The default is to
send traffic along the shortest path. Bidirectional connectivity
between nodes R_i and R_j is achieved by using two different ring
LSPs: R_i uses RL_j to reach R_j, and R_j uses RL_i to reach R_i.
2.1. Provisioning
For the purposes of RMR, a ring node R is configured with its
loopback address, the RID that it will participate in, and what link-
state IGP to use for auto-discovery. R is also configured with a
mastership value, which is used in master election. Finally, R may
be configured with the signaling protocols and OAM protocols it
supports, or these may be inferred. Note that R may participate in
multiple rings; each would have its own configuration.
To simplify ring provisioning even further, R may be made
"promiscuous" by being assigned an RID of 0. A promiscuous node
listens to RIDs in its IGP neighbors' link-state updates in order to
acquire an RID for its use. Details are in [I-D.ietf-mpls-rmr].
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2.2. Announcement
Once configured, R announces its configuration parameters in the IGP
via an RMR Node TLV. The RMR Node TLV may contain sub-TLVs; in
particular, the RMR Neighbor TLV. At a high level, these TLVs are as
follows.
[RMR Node Type][RMR Node Length][RID][Node Flags][sub-TLVs]
Ring Node TLV Structure
[RMR Nbr Type][RMR Nbr Length][Nbr Address][Nbr Flags]
Ring Neighbor Sub-TLV Structure
In IS-IS, the RMR Node TLV is a new top-level TLV. The specific
format is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length = 6+S | Ring ID (4 octets) ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... (RID continued) | Node Flags (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs, if any ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S is the total size of the sub-TLVs
Ring Node TLV Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length = n*6 | Neighbor Loopback ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... (continued, 4 octets) | Neighbor Flags (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Loopback (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Flags (2 octets) | (etc.)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n = number of neighbors included in the sub-TLV
Ring Neighbor sub-TLV Format
In OSPF, the RMR Node TLV is a new top-level TLV of the Traffic
Engineering Opaque LSA.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length = 8+S |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ring ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node Flags (2 octets) | Pad (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Pad is set to zero when sending and ignored on receipt.
S = total length of sub-TLVs
OSPF Ring Node TLV Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length = 6*N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Loopback (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Flags (2 octets) | Pad (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Loopback (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Flags (2 octets) | Pad (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... etc. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Pad is set to zero when sending and ignored on receipt.
OSPF Neighbor sub-TLV Format
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MV |SS | SO | MBZ |SU |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MV: Mastership Value
SS: Supported Signaling Protocols (10 = RSVP-TE; 01 = LDP)
SO: Supported OAM Protocols (100 = BFD; 010 = CFM; 001 = EFM)
SU: Signaling Protocol to Use (00 = none; 01 = LDP; 10 = RSVP-TE)
M : Elected Master (0 = no, 1 = yes)
Flags for a Ring Node TLV
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|RD |OAM| MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RD: Ring Direction
OAM: OAM Protocol to use (00 = none; 01 = BFD; 10 = CFM; 11 = EFM)
Flags for a Ring Neighbor TLV
3. Security Considerations
It is not anticipated that either the notion of MPLS rings or the
extensions to link-state IGPs to support them will cause new security
loopholes. As this document is updated, this section will also be
updated.
4. IANA Considerations
IANA is requested to assign a new top-level TLV for the RMR Node TLV
from the IS-IS TLV Codepoints Registry. IANA is also requested to
create a new registry for sub-TLVs of the RMR Node TLV.
IANA is also requested to assign a new top-level type for the RMR
Node TLV from the OSPF TE TLVs Registry. IANA is also requested to
create a new registry for sub-TLVs of the RMR Node TLV.
5. References
5.1. Normative References
[I-D.ietf-mpls-rmr]
Kompella, K. and L. Contreras, "Resilient MPLS Rings",
draft-ietf-mpls-rmr-03 (work in progress), October 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
5.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
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[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<http://www.rfc-editor.org/info/rfc3630>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <http://www.rfc-editor.org/info/rfc5036>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
Author's Address
Kireeti Kompella
Juniper Networks, Inc.
1133 Innovation Way
Sunnyvale, CA 94089
USA
Email: kireeti.kompella@gmail.com
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