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Advertising Generic Information in IS-IS

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Advertising Generic Information in IS-IS. draft-ietf-isis-genapp-00.txt. Les Ginsberg ... do not update hold time on receipt of IIH until BFD session ... – PowerPoint PPT presentation

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Title: Advertising Generic Information in IS-IS


1
Advertising Generic Information in IS-IS
  • draft-ietf-isis-genapp-00.txt
  • Les Ginsberg
  • Stefano Previdi
  • Mike Shand

2
Changes since previous version
  • Now a WG document
  • Standards track
  • Applicability statement

3
Applicability Statement
  • The GENINFO TLV supports the advertisement of
    application specific information in IS-IS LSPs
    which is not directly related to the operation of
    the IS-IS protocol. Information which is not
    directly used by the IS-IS Decision process
    falls into this category. The Decision Process
    is defined by ISO10589 and extended by
    RFC1195 and RFC3906.

4
Applicability Statement
  • May be interpreted to cover existing information
  • Migration to use of GENAPP is seen as desirable
  • WG is the authority

5
What existing info MIGHT be candidates for
GENAPP?
  • TE/G-MPLS sub-TLV info (from TLVs 22/23/222/223)
  • TE Mesh Group sub-TLV (TLV 242)
  • PCE sub-TLV info (TLV 242)

6
Ready for Last Call
7
IS-IS and BFD
  • draft-ietf-isis-bfd-tlv-00.txt
  • Chris Hopps
  • Les Ginsberg

8
Changes since previous version
  • Now a WG document
  • Standards track
  • TLV now includes MTID

9
Problem Statement
  • BFD used to detect IPv4/IPv6 forwarding failures
  • IS-IS PDUs do not always share fate with IP
    packets
  • Adjacencies may be established even when IP
    forwarding problems are detectable

10
  • IS-IS PDUs exchanged
  • Adjacency UP
  • BFD session requested (neighbor IP address)
  • If BFD session doesnt come up could be
  • IP forwarding failure
  • No BFD Config/Support

11
Advertise support for BFD in IIHs
Type 139 (proposed) Length of octets in the
value field (1 to 255) Value
No. of octets
-----------------------------
RRRR MTID 2
-----------------------------
NLPID 1
-----------------------------

-----------------------------
RRRR MTID 2
-----------------------------
NLPID 1
------------------------------
12
Why was MTID Added?
  • BFD sessions apply to specific topologies
  • NLPIDs are not SAFI specific

13
When BFD is supported by both neighbors
  • Hold adjacency in Init state until BFD session is
    UP
  • Bring adjacency down when BFD session goes down
  • P2P 3 way state is DOWN when BFD is down
  • LAN omit neighbor MAC address when BFD is down

14
Determining when new rules apply
  • For each MTID/NLPID shared by the neighbors, if
    BFD support is configured for both neighbors, BFD
    session must be UP to use that topology
  • At least one topology must be useable in order
    for adjacency to come up

15
MTID 0(IPv4), 2(IPv6) BFD 0/IPv4, 2/IPv6
MTID 0 (IPv4) BFD 0/IPv4
IPv4 BFD Session MUST be UP before adjacency
comes up.
16
MTID 0(IPv4), 0(IPv6) BFD 0/IPv4, 2/IPv6
MTID 0 (IPv4,IPv6) BFD 0/IPv4
Single Topology/Multiple AFIs IPv4 Session MUST
be UP before adjacency comes up.
17
MTID 0 (IPv4), 2 (IPv6) BFD 0/IPv4, 2/IPv6
MTID 0 (IPv4), 2 (IPv6) BFD 0/IPv4
Multi-topology (one AFI/topology) Normal
adjacency establishment rules. IPv4 BFD Session
MUST be UP for MTID 0 to be useable.
18
Transition enable BFD
  • Detected by addition of NLPID in BFD-TLV
  • For existing adjacencies, do not update hold time
    on receipt of IIH until BFD session is UP

19
MTID 0 (IPv4) BFD 0/IPv4
MTID 0 (IPv4) BFD 0/IPv4
  1. Adjacency is Up
  2. B configures IPv4 BFD support
  3. IIH from B includes BFD-TLV for MTID 0/IPv4
    hold time not updated
  4. BFD session comes up
  5. Normal hold time update resumes

20
Transition disable BFD
  • Detected by transition of BFD session state to
    admin down
  • For existing adjacencies, do not update hold time
    on receipt of IIH until corresponding NLPID is no
    longer advertised in BFD-TLV

21
MTID 0 (IPv4) BFD 0/IPv4
MTID 0 (IPv4) BFD 0/IPv4
  1. Adjacency is Up/BFD session Up
  2. B deconfigures IPv4 BFD support
  3. IPv4 BFD session admin down on A
  4. IIH from B has no BFD-TLV for MTID 0/IPv4
  5. Normal hold time update resumes

22
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