link state routing,unicast routing, multicast routing,broadcast routing, hierarical routing,congestion control, approach,

1. Link-State Routing
• The shortest path to a destination is not
necessarily the path with the least number
of hops

2. Link-State Routing
Link-State Routing Process
• How routers using Link State Routing Protocols reach convergence
• -Each routers learns about its own directly connected networks
• -Link state routers exchange hello packet to “meet” other directly
• connected link state routers.
• -Each router builds its own Link State Packet (LSP) which includes
information about neighbors such as neighbor ID, link type, &
bandwidth.
• -After the LSP is created the router floods it to all neighbors who
then store the information and then forward it until all routers
have the same information.
• -Once all the routers have received all the LSPs, the routers then
construct a topological map of the network which is used to
determine the best routes to a destination

3. Link-State Routing
• Directly Connected
Networks
• Link
This is an interface
on a router
• Link state
This is the
information about the
state of the links

4. Link-State Routing
Sending Hello Packets to Neighbors
• Link state routing protocols use a hello
protocol
Purpose of a hello protocol:
-To discover neighbors (that use the
same link state routing protocol) on
its link

5. Link-State Routing
Building the Link State
Packet
• Each router builds its own
Link State Packet (LSP)
Contents of LSP:
-State of each directly
connected link
-Includes information
about neighbors such
as neighbor ID, link type,
& bandwidth.

6. Link-State Routing
Flooding LSPs to Neighbors
• Once LSP are created they are forwarded out
to neighbors.
– -After receiving the LSP the neighbor continues to
forward it throughout routing area.

7. Link-State Routing
• Determining the shortest path
– The shortest path to a destination determined
by adding the costs & finding the lowest cost

8. Link-State Routing

9. Link-State Routing Protocols
Routing
protocol
Builds
Topological
map
Router can
independently
determine the
shortest path to
every network.
Convergence
A periodic/
event driven
routing updates
Use
of
LSP
Distance
vector
No No Slow Generally No No
Link State Yes Yes Fast Generally Yes Yes
Advantages of a Link-State Routing Protocol

10. Link-State Routing Protocols
• 2 link state routing protocols used for
routing IP
-Open Shortest Path First (OSPF)
-Intermediate System-Intermediate
System (IS-IS)

11. Summary
• Link State Routing protocols are also known as
Shortest Path First protocols
• Summarizing the link state process
-Routers 1ST learn of directly connected networks
-Routers then say “hello” to neighbors
-Routers then build link state packets
-Routers then flood LSPs to all neighbors
-Routers use LSP database to build a network topology map
& calculate the best path to each destination

14. Broadcasting and multicasting
• Broadcasting
– Send to every user in a network
• Multicasting
– Send to specific users in a network

15. Broadcasting routing
• N-way-unicasting
– Most straightforward way to send a broadcast
packet, to each destination is to make N copies,
one for every user. And then send one to each
user.
– Drawback: use a lot of bandwidth for one line.

16. Broadcasting routing
• Network duplication
– Using the network to create and distribute the
copies.
– Flooding, sending to all neighbors in the network.

17. Broadcasting routing: Flooding
• Uncontrolled flooding
– A fatal flaw with flooding.
• All nodes have two neighbors: Will broadcast packages
indefinitely.
• More then two neighbors: Will create a broadcast
storm.

18. Broadcasting routing: Flooding
• Controlled flooding
– SNCF(Sequence-number-controlled flooding)
• Every sender node puts its address and broadcast
sequence-number in the broadcast packet.
• Every node has a memory of the address and number
of each packet it has duplicated and sent.
• If it receives a packet in the memory it drops the
packet. If not it forward-copy it to its neighbors.

19. Broadcasting routing: Flooding
• Controlled flooding
– RPF (Reverse path forwarding)
• Only sends packet forward if it is received from the next
node in the shortest path back to the sender.

20. • Spanning-Tree Broadcast
• Limits number of sent packets.
• Creates a path for each node to forward received
packets. A so called minimum spanning-tree.
• This is done by routing algorithms.
Broadcasting routing
Creating a center based spanning-tree
A central node is defined.
Then all nodes sends a message at the same time towards
the center node until they arrive at ether the center node
or a node that’s already a part of the tree.

21. Broadcasting routing
• Spanning-Tree Broadcast

22. • Managing a group
– IGMP(Internet group management protocol).
– Provides the means for a host to inform the router
that it wants to join a multicast group.
– It has 3 message types, used for management of
the group.
• Membership_Query For joining the group
• Membership_Report For acknowledgements
• Leave_Group For leaving the group
Multicasting
A multicast packet is sent by address
indirection.
A single identifier for all the receivers.
This is done by a multicast group.

23. • Multicasting routing using a group-shared
tree.
– Similar to the spanning-tree broadcast.
– May use nodes not in the group to “jump”
between different parts of the group.
Multicasting routing algorithms
Multicasting routing using a source-based tree
•Using a RPF(reverse path forwarding) algorithm
each node gets its own spanning tree.
•This is better when many users wants to
communicate with many users.