multicasting

UCBMulticasting

Jean WalrandEECS

UCB Outline Definitions

Broadcast, Multicast, Anycast Examples

ARP, ICMP, Group Flooding Routing Multicast

Tree of shortest paths; shortest tree Multicast Backbone

Overlay Join Groups Soft State

Reliable Multicast Nacks, Aggregation

Multilayer Multicast

UCB Definitions

Broadcast One to all

Multicast One to all members of a group

Anycast One to any member of a group

UCB Examples

ARP: Broadcast to LAN (Note: VLANs) 11…11 = “broadcast” address on Ethernet

ICMP: Routers broadcast their link states in OSPF

Group: Multicast of seminar to “subscribers” Class-D IP addresses = group addresses

UCB Flooding

Send on all other ports: Remember seen packets, or Mark route on packets

B C

A

[1][1]

{1}{1}

[1] [1]

B C

A

[1]

[1; A] [1; A]

[1; A, C][1; A, B]

UCB Routing Multicast

Simplest: Tree of shortest paths Example

2

1

2

2

2

1

1

1

1

S

D1

D2

UCB Routing Multicast (continued)

Optimal: Shortest tree Example

2

1

2

2

2

1

1

1

1

S

D1

D2

UCB Routing Multicast (continued)

Comparison:

2

1

2

2

2

1

1

1

1

S

D1

D2

2

1

2

2

2

1

1

1

1

S

D1

D2

Tree of shortest paths Sum of lengths = 9

Shortest tree Sum of lengths = 8

UCB Routing Multicast (continued)

RPB: Reverse Path BroadcastRouter R sends packet received from A if A is

on the shortest path from R to S.

2

1

2

2

2

1

1

1

1

S

D1

D2

RLink ARA

UCB Routing Multicast (continued)

RPM: Reverse Path MulticastRPB + Prune back if no member of Mcast

group

2

1

2

2

2

1

1

1

1

S

D1

D2

PRLink RP

G

Not G

PrunePrunePrune

UCB

Join G

G

Routing Multicast (continued)

PIM-Dense Mode RPR + Prune + Graft (+ periodic RPR + Prune)

2

1

2

2

2

1

1

1

1

S

D1

D2

PrunePrune

GraftGraftGraft

UCB Routing Multicast (continued)

PIM-Sparse ModePeriodic Join/Prune Messages from DR to RPAssumption: Relatively few group members

UCB Reliable Multicast (continued)

ACKs do not scale NACKs may implode => NACK aggregation

1 11 1 1

1 1

UCB Reliable Multicast (continued)

ACKs do not scale NACKs may implode => NACK aggregation

2 2

2 2

UCB Reliable Multicast (continued)

ACKs do not scale NACKs may implode => NACK aggregation

3 33 3 3

3 3

NACK2

[Remember for T seconds]

UCB Reliable Multicast (continued)

Other idea: Designated Receivers

NACK n

[n]

Source

DR DR

UCB Multilayer Multicast Different channel bandwidths => Multiple Layers

SourceLayer 1

Layer 2

Random “join” experiments