Samsung Ubigate iBG3026, Configuration Manual

Page: 149 / 718

Ubigate iBG3026 Configuration Guide/Ed.00
© SAMSUNG Electronics Co., Ltd.
111
Protocol Features
The following BGP features such as aggregation, route reflection, AS
confederation, and etc will be supported on the Ubigate iBG3026 system.
Aggregation is the process of combining the characteristics of several different
routes in such a way that a single route can be advertised. Aggregation reduces
the amount of information a BGP speaker stores and exchanges with other
speakers. It can be part of the decision process to reduce the amount of routing
information that will be placed in the Adj-RIBs-Out. The general rule of route
aggregation is that routes can be aggregated if and only if the corresponding
attributes of the routes are identical.
Route reflection is used to solve the problem of full mesh IBGP in an AS with
a large number of routing nodes. Multiple BGP routers can peer with a central
server, the route reflector, and then route reflectors can peer with one another.
The BGP routers peered with the reflector exchange routing information with
it and it, in turn, passes(or reflects) the information between clients and to
other IBGP and EBGP peers.
AS confederations is a second approach to solve the scaling problem with full-
mesh IBGP sessions. This approach divides a given AS into many sub-ASs.
For other ASs, this AS doesn’t look any different from the outside. There is a
full-mesh of IBGP sessions within a sub-AS. BGP sessions between routers in
different sub-ASs(of the same confederation) are like EBGP sessions, but with
some differences. They are sometimes referred to as EIBGP sessions.
A route in the routing table may disappear and reappear intermittently. This is
known as flapping. It occurs when BGP sends a routing table and then
withdraws it. A route that appears and disappears intermittently and repeatedly,
propagates BGP UPDATE and WITHDRAW messages on to the Internet.
This excessive flow of traffic can use up bandwidth and drive up CPU
utilization of routers. Route flap dampening is used to prevent this kind of
excessive traffic due to route flapping.
Routes are categorized as either well-behaved or ill-behaved. A well-behaved
route shows a high degree of stability during an extended period of time(as
determined by configurable limits). Ill-behaved routes are no longer advertised
but suppressed until there is some indication that the route has become stable.