BGP is a routing protocol that exchanges routing information between autonomous systems to enable traffic routing between networks. It uses TCP to communicate between routers within and outside autonomous systems. BGP maintains two routing tables, one for the interior gateway protocol within an autonomous system and another for external BGP routes. It selects the best path among potentially multiple paths to a destination and installs that in the IP forwarding table.

1. Border Gateway Protocol
(BGP)

2. TEAM
 Team Members
Group 9
 Yogeshwar P.Kulkarni
 Parth Varmora
 Salman Sikinder
 Manish Parmar
 Anand Patel

3. INTRODUCTION
 BGP protocol for exchanging routing
information between gateway hosts (each with
its own router) in a network of autonomous
systems.
 he routing table contains a list of known
routers, the addresses they can reach, and a
cost metric associated with the path

4. Autonomous System (AS)
Fig:
 Collection of networks with same policy
 Single routing protocol
 Usually under single administrative control
 IGP to provide internal connectivity
AS 100

5. Overview-BGP

6.  Hosts using BGP communicate using uses TCP.
 BGP communicates with autonomous (local) networks using Internal
BGP (IBGP).
 Routers inside the autonomous network thus maintain two routing
tables: one for the interior gateway protocol and one for IBGP
 It uses path vector protocol
 Can have multiple paths for a given prefix
 Picks the best path and installs in the IP forwarding table

7. BGP state machine

8. Types Of BGP Session
 Internal BGP
 External BGP

9. BGP Routing Process

10. BGP Messages
 Open
 Announces AS ID
 Determines hold timer – interval between keep_alive or
update messages, zero interval implies no keep_alive
 Update
 Keep_alive
 Sent periodically (but before hold timer expires) to peers to
ensure connectivity.
 Sent in place of an UPDATE message
 Route-Referesh
 Notification
 Used for error notification
 TCP connection is closed immediately after notification

11. Version:
 The current version of BGP is BGP
version 4, based on RFC4271
 Previous Version: RFC 1771