This is a very interesting and complex question in my opinion. As I
understand it the classification of whether a routing protocol utilizes a
distance-vector or link-state algorithm depends on how that routing protocol
announces it's routes to the network.
With a distance-vector algorithim each device will include in it's
announcements the destinations to which it is directly attached (depending
on configuration) as well as destinations that it has heard about from other
devices (also depending on configuration and route filtering).
In contrast, in a link-state protocol, a device doesn't provide information
about destinations it knows how to reach. Instead, it provides information
about the topology (no pun intended from the previous phylosophy thread:) of
the network in its immediate vicinity. Each device announces link-states of
it's interfaces (again, depending on configuration) to all devices in the
network or area. This ensures that all devices within that area/network
have an identical database or picture of the network and can thus make
routing decisions utilizing the SPF algorithm. As you can see, using a link
state protocol will eliminate the need for route loop detection as loops
could not exist if all devices in the network have an identical view of that
network.
In my mind, though BGP doesn't neatly fall into either category being
labeled as a path-vector routing protocol, it would generally be considered
more of a distance-vector algorithm because it doesn't have a consistent
database of link-states but instead uses a table of routes that were
announced to it from a BGP peer.
EIGRP is along the same lines as far as classification is concerned. Though
it establishes adjacencies, has low convergence time, and sends
incremental/partial routing updates, it still uses the DUAL algorithm to
find the best route from a neighboring routers route table and not a
consistent link-state database. Cisco may claim this is a hybrid
link-state/distance-vector protocol, but to me it is still distance-vector.
If anything can be considered a hybrid protocol it would be OSPF as it uses
both link-state databases (intra-area routes) and distance-vector
advertisements (inter-area routes) when the ABR advertises all networks from
a non-backbone area into a backbone area. Right Howard??
-Mike Cohen
-----Original Message-----
From: cisco cabanaboy [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 26, 2000 10:59 AM
To: [EMAIL PROTECTED]
Subject: BGP
Is BGP DV, or LS?
=====
ciscocabanaboy, CCNP-Voice, CCDP, MCSE, CNX, A+, N+, I-net+, BOFH...
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