Today

1
Today

• Finish chapter 4
• Continue with chapter 5
• Change hw due date
• HW 7 is now due Mon Oct 25

2
Chapter 4 Network Layer

• 4. 1 Introduction
• 4.2 Virtual circuit and datagram networks
• 4.3 Whats inside a router
• 4.4 IP Internet Protocol
• Datagram format
• IPv4 addressing
• ICMP
• IPv6

• 4.5 Routing algorithms
• Link state
• Distance Vector
• Hierarchical routing
• 4.6 Routing in the Internet
• RIP
• OSPF
• BGP
• 4.7 Broadcast and multicast routing

3
Broadcast/Multicast

• Broadcast routing
• Source duplication is inefficient
• In-network duplication
• Flooding, controlled flooding, spanning trees
• Multicast routing
• Find tree or trees to connect all partic. Routers
• Source-based trees
• Shortest path trees (Dijkstra, same as unicast
  routing)
• Reverse Path Forwarding (RPF) trees
• Group shared trees
• Steiner tree
• Center-based trees
• Internet multicast routing DVMRP, PIM

4
PIM Protocol Independent Multicast

• not dependent on any specific underlying unicast
  routing algorithm (works with all)
• two different multicast distribution scenarios

• Dense
• group members densely packed, in close
  proximity.
• bandwidth more plentiful

• Sparse
• networks with group members small wrt
  interconnected networks
• group members widely dispersed
• bandwidth not plentiful

5
Consequences of Sparse-Dense Dichotomy

• Dense
• group membership by routers assumed until routers
  explicitly prune
• data-driven construction on mcast tree (e.g.,
  RPF)
• bandwidth and non-group-router processing
  profligate

• Sparse
• no membership until routers explicitly join
• receiver- driven construction of mcast tree
  (e.g., center-based)
• bandwidth and non-group-router processing
  conservative

6
PIM- Dense Mode

• flood-and-prune RPF, similar to DVMRP but
• underlying unicast protocol provides RPF info for
  incoming datagram
• less complicated (and less efficient) downstream
  flood than DVMRP
• has protocol mechanism for router to detect it is
  a leaf-node router

7
PIM - Sparse Mode

• center-based approach
• router sends join msg to rendezvous point (RP)
• intermediate routers update state and forward
  join msg
• after joining via RP, router can switch to
  source-specific tree
• increased performance less concentration,
  shorter paths

R1
R4
join
R2
join
R5
join
R3
R7
R6
all data multicast from rendezvous point
rendezvous point
8
PIM - Sparse Mode

• sender(s)
• unicast data to RP, which distributes down
  RP-rooted tree
• RP can extend mcast tree upstream to source
• RP can send stop msg if no attached receivers
• no one is listening!

R1
R4
join
R2
join
R5
join
R3
R7
R6
all data multicast from rendezvous point
rendezvous point
9
Discussion Questions

• TRUE or FALSE
• When a host joins a multicast group, it must
  change its IP address to be that of the multicast
  group it is joining.
• In RPF, a node will receive multiple copies of
  the same packet.
• In RPF, a node may forward multiple copies of a
  packet over the same outgoing link.
• How can multicast apps learn the identities of
  the hosts that are participating in a multicast
  group?
• How can the application be certain that only
  authorized recipients get the multicast data?

10
Network Layer summary

• What weve covered
• network layer services
• routing principles link state and distance
  vector
• hierarchical routing
• IP
• Internet routing protocols RIP, OSPF, BGP
• whats inside a router?
• IPv6

• Next stop
• the Data
• link layer!