One document matched: draft-kompella-isis-ospf-rmr-00.xml

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<rfc category="std" docName="draft-kompella-isis-ospf-rmr-00"
     ipr="trust200902">

<front>
  <title>IGP Extensions for Resilient MPLS Rings</title>

  <author initials="K." surname="Kompella" fullname="Kireeti Kompella">
    <organization>Juniper Networks, Inc.</organization>
    <address>
      <postal>
	<street>1133 Innovation Way</street>
	<city>Sunnyvale</city>
	<region>CA</region>
	<code>94089</code>
	<country>USA</country>
      </postal>
      <email>kireeti.kompella@gmail.com</email>
    </address>
  </author>

  <date/>

  <area>Routing</area>
  <workgroup>IS-IS OSPF</workgroup>

  <keyword>MPLS</keyword>
  <keyword>ring</keyword>
  <keyword>transport</keyword>

  <abstract>
    <t>
      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.
    </t>
  </abstract>

  <note title="Requirements Language">
    <t>
      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 <xref target="RFC2119"/>.
    </t>
  </note>
</front>

<middle>
  <section title="Introduction" anchor='intro'>
    <t>
      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 <xref target="I-D.ietf-mpls-rmr"/> describes the
      motivations and operation of RMR.
    </t>
    <t>
      RMR uses protocols such as IS-IS <xref target="RFC5305"/> and
      OSPF<xref target="RFC3630"/> for auto-discovery, and RSVP-TE
      <xref target="RFC3209"/> and LDP <xref target="RFC5036"/> for
      signaling LSPs.  This document gives the specifics of
      Type-Length-Value (TLV) formats for IS-IS and OSPF.
    </t>

    <section title='Definitions'>
      <t>
	For a more detailed description, see
	<xref target='I-D.ietf-mpls-rmr'/>.
      </t>
      <t>
	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.
	<figure anchor='Fig1' title="Ring with 8 nodes">
	  <artwork align='center'>

                  R0 . . . R1                 
                .             .               
             R7                 R2            
Anti-     |  .        Ring       .  |         
Clockwise |  .                   .  | Clockwise
          v  .      RID = 17     .  v         
             R6                 R3            
                .             .               
                  R5 . . . R4                 
	  </artwork>
	</figure>
      </t>
      <t>
	The following terminology is used for ring LSPs:
	<list style="hanging">
	  <t hangText="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.
	  </t>
	  <t hangText="Ring node:">
	    A member of a ring.  Note that a device may belong to
	    several rings.
	  </t>
	  <t hangText="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.
	  </t>
	  <t hangText="Ring master:">
	    The ring master initiates the ring identification process.
	    Mastership is indicated in the IGP by a two-bit field.
	  </t>
	  <t hangText='Ring neighbors:'>
	    Nodes whose indices differ by one (modulo ring size).
	  </t>
	  <t hangText='Ring links:'>
	    Links that connnect ring neighbors.
	  </t>
	  <t hangText='Express links:'>
	    Links that connnect non-neighboring ring nodes.
	  </t>
	  <t hangText='Ring direction:'>
	    A two-bit field in the IGP indicating the direction of a
	    link.  The choices are:
	    <list style='hanging'>
	      <t hangText='UN: 00'> undefined link </t>
	      <t hangText='CW: 01'> clockwise ring link </t>
	      <t hangText='AC: 10'> anticlockwise ring link </t>
	      <t hangText='EX: 11'> express link </t>
	    </list>
	  </t>
	  <t hangText='Ring Identification:'>
	    The process of discovering ring nodes, ring links, link
	    directions, and express links.
	  </t>
	</list>
      </t>
      <t>
	The following notation is used for ring LSPs:
	<list style="hanging">
	  <t hangText="R_k:">
	    A ring node with index k.  R_k has AC neighbor R_(k-1) and
	    CW neighbor R_(k+1).
	  </t>
	  <t hangText="RL_k:">
	    A (unicast) Ring LSP anchored on node R_k.
	  </t>
	  <t hangText="CL_jk:">
	    A label allocated by R_j for RL_k in the CW direction.
	  </t>
	  <t hangText="AL_jk:">
	    A label allocated by R_j for RL_k in the AC direction.
	  </t>
	  <t hangText="P_jk (Q_jk):">
	    A Path (Resv) message sent by R_j for RL_k.
	  </t>
	</list>
      </t>
    </section>
  </section>

  <section title="Theory of Operation">
    <t>
      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.
    </t>
    <t>
      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.
    </t>

    <section title="Provisioning">
      <t>
	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.
      </t>
      <t>
	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
	<xref target='I-D.ietf-mpls-rmr'/>.
      </t>
    </section>

    <section title='Announcement'>
      <t>
	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.
	<figure title='Ring Node TLV Structure'>
	  <artwork align='center'>
[RMR Node Type][RMR Node Length][RID][Node Flags][sub-TLVs]
	  </artwork>
	</figure>
	<figure title='Ring Neighbor Sub-TLV Structure'>
	  <artwork align='center'>
[RMR Nbr Type][RMR Nbr Length][Nbr Address][Nbr Flags]
	  </artwork>
	</figure>
      </t>
      <t>
	In IS-IS, the RMR Node TLV is a new top-level TLV.  The
	specific format is as follows:
	<figure title='Ring Node TLV Format'>
	  <artwork align='center'>
 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
          </artwork>
	</figure>
	<figure title='Ring Neighbor sub-TLV Format'>
          <artwork align='center'>
 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
          </artwork>
	</figure>
      </t>
      <t>
	In OSPF, the RMR Node TLV is a new top-level TLV of the
	Traffic Engineering Opaque LSA.
	<figure title='OSPF Ring Node TLV Format'>
          <artwork align='center'>
 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
          </artwork>
	</figure>
	<figure title='OSPF Neighbor sub-TLV Format'>
          <artwork align='center'>
 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.
          </artwork>
	</figure>
	<figure title='Flags for a Ring Node TLV'>
          <artwork align='center'>
 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)
          </artwork>
	</figure>
	<figure title='Flags for a Ring Neighbor TLV'>
          <artwork align='center'>
 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)
          </artwork>
	</figure>
      </t>
    </section>
  </section>

  <section title='Security Considerations' anchor='sec-con'>
    <t>
      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.
    </t>
  </section>

  <section anchor="IANA" title="IANA Considerations">
    <t>
      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.
    </t>
    <t>
      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.
    </t>
  </section>
</middle>

<back>
  <references title='Normative References'>
    <?rfc include='reference.RFC.2119'?>
    <?rfc include='reference.I-D.ietf-mpls-rmr'?>
  </references>
  <references title='Informative References'>
    <?rfc include='reference.RFC.3209'?>
    <?rfc include='reference.RFC.3630'?>
    <?rfc include='reference.RFC.5036'?>
    <?rfc include='reference.RFC.5305'?>
  </references>
</back>
</rfc>