Multicast

1
Multicast

• Bernard Cousin

2
Multicast group members

• Bernard Cousin (prof.)
• Raymond Marie (prof.)
• Miklos Molnar (ass. prof.)
• Ali Boudani (PhD)
• Alexandre Guitton (PhD)

3
Introduction

• Multicast tree
• Tree fusion algorithm
• Over WDM network with sparce splitting capacity
• Multicasting over MPLS
• Small group multicast
• Simple Explicit Multicast
• Segmentation

4
Multicast tree

• Cost of multicast communication is proportional
  to the length of the tree
• more efficient heuristics are needed
• A new family of heuristics
• connecting sub-trees with minimal Steiner trees

- one solution18-117
11
- our solution 25-223
5
Domains of use of our heuristics

• Multicast tree between routing domains
  interconnected by a backbone network
• Well known greedy algorithms can be improved
  Kruskal heuristic, Takahashi-Matsuyama algorithm

6
Light-tree construction in WDM

• Splitting in optical switches is very expensive
• only few switches can split
• Application of our heuristics for sparse
  splitting capable networks
• The number of wavelengths and/or wavelength
  channels required to build the multicast tree is
  lower

7
Multicast tree over MPLS

• In a MPLS domain, usually
• packets is forwarded over the LSP ending at the
  edge LSR associated to the packet destination
• paths followed by multicast packets will not be
  efficient

MPLS domain
LSP
ingress LSR
egress LSR
8
Branching nodes

• Multicast trees have
• few branching nodes
• many non-branching nodes
• A branching node
• a router with distinct next hops for a multicast
  tree

from REUNITE study
from our study
9
MPLS Multicast Tree

• uses LSPs between branching nodes
• no multicast states into no-branching nodes
• enhances scalability of MPLS domain for multicast
  trafic

10
Xcast solution

• Explicit multicast Boivie al.
• Xcast packet
• explicit list of group members
• list of unicast addresses in Xcast packet header
• No multicast routing table
• standard unicast routing protocol
• no additionnal entry
• No management protocol

11
Xcast packet forwarding
d4, G
E
d1
A
B
D
F
d3, G
s1
dest next hop
grp list of dest
G d1,d2,d3
d1 E
d2 C
C
d2, G
d3 D
d4 D
- Lookup for every destinations into Xcast
packet - Forward a copy of the packet (with an
appropriated destination list) for every distinct
next hop
12
Xcast problems

• Membership management
• delegated to another protocol
• multicast source knows somehow the IP address of
  every member of the multicast group
• When size of multicast group increases
• size of destinations list increases
• packet processing time increases
• packet length increases

13
SEM principles

• Use of the next branching node address as
  Destination address of IP packet
• no specific treatment into routers which are
  between branching nodes
• SEM packet header encapsulates Multicast group
  address
• processed by branching nodes
• increasing of packet length is low

14
Segmentation for XCast

• Overhead of Xcast increases with the increasing
  of the number of destinations
• best tradeoff between path-MTU length and maximum
  number of destinations into a Xcast packet
• proposition of GXcast protocol a generalization
  of Xcast
• partition of the set of destinations based on the
  optmized size of the parts
• how to find the best partition still an open
  question

15
Next following years

• Multicast tree algorithm
• Link capacities change multicast trees should
  maximize the probability of a good cost (delay,
  bandwith, etc.)
• Goal multicast routing with maximal probability
  of the requested QoS
• Xcast and mobility
• Dependable Multicast Tree
• in high speed access network
• in ad'hoc network

16
Results

• SEM.
• MMT.
• Drafts, articles, NS.

17
SEM routing table

• SEM entry (in every lts,Ggt branching node)
• multicast session lts,Ggt
• previous branching node
• list of next branching nodes
• No additional entry (in others nodes)
• standard unicast entry
• destination D next hop

18
SEM data forwarding
multicast session next branching nodes
lts1,Ggt F,C
grp next branching nodes
G B
d4, G
E
d1
A
B
D
F
d3, G
s1
C
d2, G
19
SEM protocol

• SEM control messages
• Join message (optionnal)
• Branch message
• Previous_branch message
• Alive message
• Leave message

20
Join process

• By SEM message or any other means (e.g. other
  multicast protocols)
• The source gets the list of all destination
  routers associated with the multicast session
• lts, Ggt destination router
• designated routeur of a IP network where at less
  one host station is a member of the multicast
  session lts, Ggt

21
Join transmission
grp next branching nodes
G C
G C
d4, G
d4, G
E
d1
E
d1
d3-gts1 SEM, join F to lts1,Ggt
F-gts1 SEM, join F to lts1,Ggt
A
B
D
F
d3, G
s1
A
B
D
F
d3, G
s1
dest nexts
G C F
dest next hop
grp list of dest routers
G C F
... ..., ...
... ..., ...
C
d2, G
C
d2, G
22
Branch process

• Branching nodes discovery process
• Branch messages are sent by the source toward
  every destinations routers
• periodically
• Previous_branch messages are sent back toward
  previous branching nodes

23
Branch transmission
multicast session next/prev branching nodes
lts1,Ggt F,C/s1
grp next branching nodes
G C
G C
d4, G
E
d1
s1-gtG SEM, lts1,Ggt Branch C,F/s1
A
B
D
F
d3, G
s1
G C F
grp list of dest routers
dest next hop
G C, F
dest next hop
d1 E
d2 C
d1 E
C
d2, G
d3 D
d2 C
d4 D
d3 D
F D
d4 D
C -
F B
C B
24
Previous-branch transmission
multicast session next/prev branching nodes
lts1,Ggt F,C/s1
grp next branching nodes
G
B
C
d4, G
E
d1
A
B
D
F
d3, G
s1
G C F
grp list of dest routers
dest next hop
G C, F
dest next hop
d1 E
d2 C
d1 E
C
d2, G
d3 D
d2 C
d4 D
d3 D
F D
d4 D
C -
F B
C B
25
Terminal Previous_branch
multicast session next/prev branching nodes
lts1,Ggt FC/s1
grp next branching nodes
G B
d4, G
E
d1
A
B
D
F
d3, G
s1
G C F
grp list of dest routers
dest next hop
G C, F
dest next hop
d1 E
d2 C
d1 E
C
d2, G
d3 D
d2 C
d4 D
d3 D
F D
d4 D
C -
F B
C B
26
Alive transmission
multicast session next/prev branching nodes
lts1,Ggt F,C/s1
lts2,Kgt F/s2
grp next branching nodes
G C
G B
d4, G
E
d1
s2
A
B
D
F
d3, G
s1
G C F
grp list of dest routers
dest next hop
G C, F
dest next hop
d1 E
d2 C
d1 E
C
d2, G
d3 D
d2 C
d4 D
d3 D
F D
d4 D
C -
F B
C B
27
Leave message
grp next branching nodes
G C
G B
d4
E
d1
E
d1
d3-gts1 SEM, join F to lts1,Ggt
F-gts1 SEM, leave F from lts1,Ggt
A
B
D
F
d3
s1
A
B
D
F
s1
dest nexts
G C F
dest next hop
grp list of dest routers
G C - F
... ..., ...
... ..., ...
C
d2, G
C
d2, G
28
SEM performance evaluation
29
SEM performance evaluation
30
SEM performance evaluation
31
Conclusion

• SEM
• packet forwarding process
• SEM multicast routing protocol
• SEM assumptions few branching nodes
• no entry in multicast routing table in
  no-branching nodes
• low data packet length increasing

32
SEM comparison

• SEM - XCAST
• XCAST has no management protocol
• SEM/REUNITE
• SEM/HBH