Exterior Gateway Protocol
An Exterior Gateway Protocol ( EGP ) is used to exchange accessibility information between autonomous systems (AS), i.e. H. Information about which networks can be reached. The routers of the autonomous systems then put this data into internal routing information for intradomain routing protocols such as B. OSPF or Routing Information Protocol (RIP).
Functions
An EGP has three main functions:
- Define neighbors: Two routers from two different AS agree with each other whether they want to become EGP partners.
- Accessibility of the neighbors: A check is made at certain time intervals to see whether the EGP partners can still be reached.
- Accessibility of networks: EGP partners receive a list of reachable networks in the autonomous systems of the neighbors on request. This is the main role of EGP.
history
The original Exterior Gateway Protocol was specified by Eric C. Rosen and David L. Mills in the early 1980s. This protocol is no longer used today, but its name has been generalized over time to the general term for the class of routing protocols described above.
The successor to the original EGP is the Border Gateway Protocol (BGP) developed in the early 1990s , which is still used today. As an intelligent protocol, it is able to operate route optimization on the basis of existing EGP data and thereby reduce time lost when setting up new routes to a minimum.