Download Routing

BY,
P.B.SHANMATHI
ROUTING:
It is a process by which routing table is built.
Forwarding :
Select an output port based on routing table.
Routing table :
Mapping from network address to next hop.
Forwarding table :
Mapping from a network number to an
outgoing interface.
Network graph:
• Forward’s packet
lowest cost path.
• Can calculate shortest path and load them into
non volatile storage.
PROBLEMS:
1.Does not deal with node or link failure.
2.Does not consider addition of new nodes or link.
SOLUTION:
I. Distance vector routing algorithm.
II. Link state algorithm.
DV algorithm: (bellman ford algorithm)
• Router sends its table to its neighbour for every t
seconds
• It updates the table based on new informations.
COUNT TO INFINITY:
when the number of hops counts more
than one it is said to be count to infinity.
SPLIT HORIZON TECHNIQUE:
• achieved by poison reverse.
• prevent loop in routing.
• information about the routing for a particular packet is
not sent in same direction.
RIP- ROUTING INFORMATION PROTOCOL
• Straight forward implementation of distance
vector routing.
• Sends an update message for every updates .
RIP V2 packet format
Command
version
must be zero
family on net 1
route taps
Address prefix of net1
Mask of net1
Distance of net1
family of net2
route taps
Address prefix of net2
Mask of net2
Distance of net2
LINK STATE ROUTING:
Send to all nodes information about directly
connected links .
LINK STATE PACKET (LSP)
• ID of the node.
• Cost of link to each directly connected nodes.
• Sequence number.
• Time to live (TTL).
RELIABLE FLOODING :
• Stores , forwards, generates the LSP.
• Sequence no= 0 , when reboot.
GLOBAL INTERNET PROTOCOL :
NSF NET
BACKBONE
BARNET
WESTSIDE
REGIONAL
NACR
STANFORD
BERKLEY
MIDNET
LA
UNIV
FS
BACKBONE SERVICE PROVIDER
LARGE CORPORATION
BACKBONE SERVICE
PROVIDER
CONSUMER ISP
PEERING POINT
CONSUMER ISP
SMALL CORPORATION
AUTONOMOUS SYSTEM
( ROUTING DOMAIN)
• Corresponds to an administrative domain.
• Eg. University, company etc….
NETWORK WITH 2 AUTONOMOUS SYSTEM:
R1
R3
R2
R5
R6
R4
INTER DOMAIN ROUTING PROTOCOLS:
 EGP- EXTERIOR GATEWAY PROTOCOL.
 BGP- BORDER GATEWAY PROTOCOL.
BGP:
It is a collection of set of ASS.
internet consist of connection of multiple
backbone networks called service providers.
service provider may be private or
government .
backbone
providers
large companies
backbone providers
ISP
small
companies
consumers
BGP4:
• it defines local traffic as traffic that originates at
(or) terminates on nodes within autonomous
system.
• Transit traffic – traffic passing through AS.
Types of AS :
 Stub AS
 Multihomed AS
 Transit AS
Stud AS:
single connection to one other AS.
carry only local traffic.
eg- small cooperation.
Multihomed AS:
connected with more than one other AS.
refuses to carry transit traffic.
eg- large corporations.
Transit AS:
it has more connection and designed carry
both transit and local traffic.
(backbone)
AS :
• it has speaker .
• Has one or more border gateways which are
routers.
• Through routers packets leaves AS.
• It advertises complete path with list of
autonomous system to reach a particular network.
BGP issues:
1. AS number should be unique.
2. AS number are 16 bits number assigned ny a
central authority.
Internet Protocol Version 6 (IPV6) 128
bits
•
•
•
•
•
•
It is a next generation IP.
Supports real time service.
Supports multicast.
Supports authentication and security mechanism.
Supports auto configuration.
Enhance routing functionality including support
for mobile host.
• Address notation
– X:X:X:X:X:X:X:X
IPv6 header
Version
Traffic
Flow label
Payload length
Next header
HOP
Source address
Destination address
Header data
Internet Multicast:
• one to many multicast.
One to many multicast:
Source specific multicast(SSM) :
A receiving host specifies both a multicast
group and sending host.
Many to many multicast (ASM):
A host signal decides to join or leave a group
by communicating with its local route using special
protocol.
IPv4
IPv6
IGMP ( Internet Group Management
Protocol)
MLD ( Multicast Listener Dictionary)
TYPES:
1. Distance vector Multicast Routing Protocol:
router already knows the shortest path
through the source n goes to router n.
it eliminates broadcast packets by
 parent for LAN (relative to S) forward
 Shortest path to S (leave via DV)
 Smallest address to break ties.
Network layer :
IGMP
ICMP
IP
ARP
each multicast router needs to know the list
of groups that have atleast one loyal member
related to each interface
Collection of this time of information is alone
at two levels .
a. Locally  IGMP
b. Globally  DVMRP , PIM
Common multicast protocol:
multicast
protocols
Source
Based
MOSPF
group
based
DVMRP
DM
SM
CBT
DIM
DVMRP- an interior gateway protocol.
only rout multicast datagrams.
IGMP – used for discovery of host in multicast group.
DVMRP routs multicast datagram within an AS
DVMRP – Packet
Type
Reserved
Code
Checksum
Minor version
(0xFF)
Major Version
(3)
This is portion of packet
Type – indicates it is a DVMRP packet.
Code – indicates the type of DVM of the packet code
Checksum – to detect error.
Minor and major versions – indicates the current
version of DVMRP.
Minor = 0XFF Major = 3
PIM – Protocol Independent Multicast
0
31
Version =2
Type
Reserved
Checksum
message type
PIM- DM ( dense multicast )
Implicitly built’s shortest path tree by
flooding multicast traffic domain.
PIM-SM (sparse multicast )
Explicitly built’s shortest path tree to a route
for group and creates shortest path tree .