>Thanks for the response Howard.
>
>>It's an "urban legend" that classful vs. classless has ANYTHING to do
>>with something being link state or distance vector. It's a
>>historical accident that the first dynamic routing protocols,
>>developed when there was no such thing as classless addressing, were
>>distance vector. Indeed, RIPv2 is fully classless although a quite
>>old design.
>
>If this is the case, then why didn't Cisco just call EIGRP a
>link-state routing protocol?
Because EIGRP is in no way link state. It's advanced distance vector,
according to the designer of its algorithms, Cisco implementers such
as Dino Farinacci, etc. The internal tables you can display with a
show command are characteristic of distance vector, not link state.
>The fact that EIGRP uses classful network statements seemed like the
>only thing that differentiates it from OSPF.
Totally different internal protocols and algorithms.
Classful and classless have NOTHING to do whether a protocol is link
state or distance vector.
>It doesn't make sense why they wouldn't abandon the idea of distance
>vector and just call it link-state.
Distance vector is not an obsolete approach, if it's modern distance
vector. It typically is less CPU intensive than link state, may be
less memory intensive, and, may be more tolerant of certain routing
failure modes. On the other hand, link state is often faster and more
accurate as long as the routing updates are not errored. OSPF and
ISIS have standards-based mechanisms for distributing other
information, which will be used in such things as traffic engineering.
There are issues of proprietary versus standards based protocols, but
you will find quite a few routing researchers arguing link state
versus distance vector.
>
>Thanks in Advance,
>Fred
>
>
>>From: "Howard C. Berkowitz" <[EMAIL PROTECTED]>
>>Reply-To: "Howard C. Berkowitz" <[EMAIL PROTECTED]>
>>To: [EMAIL PROTECTED]
>>Subject: Re: Hybrid Routing Protocols
>>Date: Wed, 31 Jan 2001 15:49:55 -0500
>>
>>"Hybrid" routing protocol is a marketing term, not a technical one,
>>which is an attempt to differentiate EIGRP from older distance
>>vector, and standards-based link state, protocols.
>>
>>EIGRP uses the Diffusing Update algorithm invented by JJ
>>Garcia-Luna-Aceves while he was at Stanford Research Institute. He
>>was not involved in Cisco's EIGRP implementation, and indeed has
>>published several new algorithms he believes faster than DUAL, such
>>as Link Vector Algorithm with Sequence Numbers (LVA-SEN). JJ, when I
>>last looked, is on the faculty of USC Santa Cruz.
>>
>>Simplifying a great deal, distance vector routers exchange their
>>routing tables (subject to split horizon) with their neighbors, add
>>their incremental link costs to the routes received, and pick the
>>best routes. Link state protocols exchange information about routers
>>and directly connected links, including accurate copies of this
>>information from non-neighboring routers, and independently create
>>routing tables.
>>
>>Distance vector protocols are sometimes called Bellman-Ford or
>>Distributed Bellman-Ford, while link state are sometimes called
>>Dijkstra. These names refer only to parts of the algorithm
>>
>>I tend to think of generations of distance vector protocols:
>>
>>1st (IP RIP, RTMP, XNS RIP): hop count metric, periodic plus
>>optional triggered update, loop prevention through split horizon and
>>basic holddown, loop detection through count to infinity, unreliable
>>transfer of routing updates
>>
>>2nd (IGRP, IPX RIP): bandwidth/delay metric, periodic plus optional
>>triggered update, loop prevention through split horizon and basic
>>holddown, loop detection through sensing monotonically increasing
>>metric or count to infinity, unreliable transfer of routing updates
>>
>>3rd (EIGRP): bandwidth/delay metric, updates on change only,
>>loop-free route computation algorithm, reliable transfer of routing
>>updates
>>
>>BGP's path vector algorithm is a variant on distance vector.
>>
>>> I just a general question about routing protocols, if anyone
>>>could help
>> >me out here I'd be grateful.
>>> When comparing EIGRP to Distance Vector routing protocols, like RIP,
>>>the only similarity that I noticed was that the network statements are both
>>>classful.
>>
>>It's an "urban legend" that classful vs. classless has ANYTHING to do
>>with something being link state or distance vector. It's a
>>historical accident that the first dynamic routing protocols,
>>developed when there was no such thing as classless addressing, were
>>distance vector. Indeed, RIPv2 is fully classless although a quite
>>old design.
>>
>>
>>>Is this the only characteristic that prevent EIGRP from being
>>>considered a total link-state routing protocol? Or is there something else I
>>>failed to notice?
>>>
>>>
>>>Thanks in Advance,
>>>Freddy Krugar III
>>
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