TRANSPORT LAYER
BY,
Parthasarathy.g
Overview of Transport Layer
Make communication among applications
running on different hosts.
Sender Side: breaks applications messages into segments
Receiver Side: Reassemble segments into messages passes to
application layer.
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
family on net 1
version
must be zero
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
REGIONAL
WESTSIDE
NACR
STANFORD
BERKLEY
MIDNET
LA
UNIV
FS
BACKBONE SERVICE PROVIDER
LARGE CORPORATION
BACKBONE SERVICE
PROVIDER
CONSUMER ISP
PEERING POINT
CONSUMER ISP
AUTONOMOUS SYSTEM
( ROUTING DOMAIN)
 Corresponds to an administrative domain.
 Eg. University, company etc….
NETWORK WITH 2 AUTONOMOUS SYSTEM:
R1
R3
R2
R5
R4
R6
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.
2.
AS number should be unique.
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 .