1. (ed) Peter Ashwood-Smith
IS-IS Extensions Supporting IEEE 802.1aq Shortest Path Bridging
David Allan
(ed) Peter Ashwood-Smith
Nigel Bragg
(ed) Don Fedyk
Paul Unbehagen]
IETF 78 Maastricht / July 2010

2. FORWARDING ON THESE FIELDS ONLY
IEEE wishes to provide SPF/L2VPN routing to existing Ethernet ASIC based data paths
2005
2008
1998
B-VID
I-TAG
B-TAG
B-DA
B-SA DA SA
Ethertype
C-VID
Q-TAG
S-VID
C-TAG
S-TAG
I-SID
Ethernet
802.3
Provider
Backbone
Bridges
802.1ah
802.1ad
VLAN
Mac in Mac
Q in Q
FORWARDING ON THESE FIELDS ONLY
BECAUSE ….
USING THESE DATAPATHS

3. They are routed with distance vector style protocol(s) (
They are routed with distance vector style protocol(s) (*)STP that create trees .. not ideal at larger scales because…
2 – long way from
shortest paths..
1- Can’t use these links
SOURCE
A1.. A100
ROOT
DEST
3 - LEARN A1..A100 on tree..

4. We wish to achieve this…..
All links usable
Shortest Paths
Equal Cost x N
Animation Courtesy of
Guoli Yin
AND …

5. An L2VPN (E-LAN) with 7 members
Support logical connectivity (L2VPN)
An L2VPN (E-LAN) with 7 members
Want to have single point membership provisioning.
Want automatic unicast and multicast forwarding.
Want existing Ethernet OA&M to work unchanged.
This causes requirements for symmetric and congruent unicast/multicast.
Animation Courtesy of
Guoli Yin

6. The set of all pruned SPF trees for a given VPN is referred to as an “active topology” for that VPN service.
Active topology for VPN instance with 8 members.

7. IS-IS is the logical choice
Topology discovery
Each bridge is aware of the physical topology
We add a new link metric just for SPB.
Service discovery
VPN membership is included “ISID”.
Calculations produce FIB: [DA, VID] => NextHop(s)
16 different variations (ECT-ALGORITHMs)
produces different Equal cost behaviors isolate by VID.

8. 802.1aq ISIS LSP extensions at a glance
LSPID Seq Num Checksum ….
x a 0xc01f …..
SOURCE
HOST NAME Instance_1
NLPID SPB (0xC1)
AREA ADDR
NBR ID COST: 10
NBR ID COST: 10
SPSOURCEID
SPB ECT-ALGORITHM 1 ECT-VID 101
SPB ECT-ALGORITHM 0 ECT-VID 100
SPB BMAC
ECT-VID
SPB ISID T&R
ECT-VID
SPB ISID T&R
(1) :4 10
(2)
255
(3) :1 :3 10
256
(4)
LSP fragment for node :1 with 2 peers :4 and :3 and two services 255, 256
(5)

9. SPB sub-TLV layout
| PDU |TLV | SUB-TLV | TYPE | TYPE | #OCCURRENCE | IIH MT-Port-Capability SPB-B-VID SPB-Digest
LSP MT-Capability SPB-Inst SPB-I-OALG >= SPBM-SI >= SPBV-ADDR >= MT-Intermediate-System SPB-Metric SPB-A-OALG >=0

10. SPB specific Link Metric - nodal
|Type=SPB-Metric| = | Length | (1 byte) | SPB-LINK-METRIC | (3 bytes) | Num of ports | (1 byte) | Port Identifier | (2 bytes)
Provides a the link metric used for min sum optimization in Disjkstra.
When link metrics differ in each direction uses MAX of both.
Independent of IP link metrics.
Additional identifiers used for construction of a single CIST.
P2P links only.

11. SPBM Service Identifier (VPN membership) - nodal
|Type = SPBM-SI | = | Length | (1 byte) | B-MAC ADDRESS | | B-MAC ADDRESS (6 bytes) | Res. | Base-VID (12 bits) | |T|R| Reserved | ISID # | |T|R| Reserved | ISID # | |T|R| Reserved | ISID #n |
The work-horse sub-TLV
Indicate that a particular node hosts members of a VPN (ISID).
Indicates properties (Transmit/Receive) of that member
Allows additional addresses B-MACs for multi homing etc.

12. SPB Instance Identifier - nodal
|Type = SPB-Inst| = | Length | (1 byte) | CIST Root Identifier (4 bytes) | | CIST Root Identifier (cont) (4 bytes) | | CIST External ROOT Path Cost (4 bytes) | | Bridge Priority | (2 bytes) |R R R R R R R R R R R|V| SPSOURCEID | | Num of Trees | (1 bytes) | VLAN-ID (1) Tuples (8 bytes) | | VLAN-ID (N) Tuples (8 bytes) |
A nodes properties – described to all other nodes.
VIDs in use, what algorithms associated with VID
Data path modes etc.

13. Hello Extensions IIH
|Type=SPB-Digest| = | Length | (1 byte) | MCID (50 Bytes) | | Aux MCID (50 Bytes) | | Agreement Digest (32 Bytes) | |RES | A | D|
|Type= SPB-B-VID| = | Length | (1 byte) | ECT - VID Tuple (1) (6 bytes) | | | | ECT - VID Tuples (N) (6 bytes) |