1. draft-liu-pim-single-stream-multicast-frr-01
Single stream Multicast Fast ReRoute SMFRR
draft-liu-pim-single-stream-multicast-frr-01
Hui Liu
Lianshu Zheng
Tao Bai
Yunfu Yu
79th IETF, Nov 2010, Beijing

2. Contents Problem Statements Characteristics Principle Fault Processing
Multicast FRR Attribute

3. Problem Statement
IP multicast video service usually has more strict availability requirements to improve user experience
But recovery time on failure is long due to delay of unicast route convergence and PIM message relaying
Multicast FRR is required to facilitate fast switchover
Several multicast FRR solutions proposed, each with its advantages and limitations

4. Characteristics
A multicast only FRR method not necessarily relying on unicast IPFRR techniques
Pre-establish protection path which does not carry service data (or 1:1 protection)
Provide protection for one-hop link/node, an entire path, or a tree, with different implementation complexity
Achieve acceptable switchover speed (100ms level) with low consumption of bandwidth resources
But on the other hand require extension of PIM protocol

5. Principle
Use PIM Primary join (PJ) and Backup join (BJ) to setup primary and backup paths from initiating point
Identify BJ by including new attribute (i.e. Multicast FRR Attribute) in PIM BJ messages
Forward service data on primary path and block backup path for forwarding
Activate backup path forwarding during failure

6. Option 1- Disabling only root node
C sends PJ from primary incoming IIF1 to
establish primary path A-B-C carrying
normal multicast stream
C also sends BJ from backup incoming
interface IIF2 to form backup path A-D-C
D creates normal forwarding entries and
relays BJ towards A
A creates non-forwarding entries with
disabled outgoing interface OIF1 and
terminates BJ
If failure on A-B-C is detected, A is notified
and is activated for multicast forwarding.
Source A
OIF1 D B C
IIF1
IIF2 PJ BJ
Data
Receiver
Applicable when primary and backup paths are disjointed

7. Option 2- Disabling all backup nodes
Source/ Upstream Neighbor
C setups primary path A-B-C and backup
path A-E-C, disabling OIF1 and OIF2
D setups primary path B-C-D and backup
path B-F-D, disabling OIF3 and OIF4
For one-hop protection, BJ only carry
primary incoming interface ID to correlate
with backup entries (IIF2 for A-B-C, and
IIF3 for B-C-D), only one-hop upstream of
initiating point is protected.
For multiple-hop protection, multiple
interface IDs on primary path are carried
(IIF1 and IIF2 for A-B-C, and IIF2 and IIF3
for B-C-D), multiple hops upstream of
initiating point are protected
Fault notification carry failure Interface ID
to enable related backup entries A
OIF1
IIF1
OIF3 B
OIF2 E
IIF2 C
OIF4 F
IIF3
Receiver1
IF1 PJ D BJ
Data
Receiver2
Applicable almost to all multicast topology by precise control

8. Fault Processing Detect failure by regular detection measures
o BFD, loss detection, low-layer alarming, and etc.
Notify the failure to backup node
o For opt.1, only root of backup path needs to be notified
o For opt.2, each backup node should be notified
Alternatives for fault notification:
o Flood notification packets (e.g. via BFD)
- Applicable to both options
- Simple and fast, but inefficient and insecure
o Multicast forward fault notification packet
- More suitable for opt.2
- Fault notification tree has to be pre-established
o Other control plane measures: sometimes too slow

9. Multicast FRR Attribute
F/E/Length: follow the same definition as RFC5384
Attr_Type: new value assigned for multicast FRR attribute
Flags: indicate the PIM join type and protection mode
Path Count: number of Path IDs carried in this attribute
Path ID: path or interface identification, may be set to an
interface ID or a logical number

10. Is it appropriate to be adopted as a working item?
Thanks !