Howard,
as per usual ...your reply was both interesting and extremely usefull
many thanks
P.S ... i too am interested in bieng a beta-tester for your new book..
>From: "Howard C. Berkowitz"
>Reply-To: "Howard C. Berkowitz"
>To: [EMAIL PROTECTED]
>Subject: Re: Is EIGRP a DV or LS protocol [7:10657]
>Date: Mon, 2 Jul 2001 13:51:04 -0400
>
> >Ahhhhhhhh.......
> >
> >that old debate........ ( i am waiting for howard to comment )
> >
> >but as far as your answer is consernced ......it`s distance vector HYBRID
> >
> >a lot of the instructor`s i know read it like this .....
> >
> >EIGRP is based on IGRP ...so it`s distance vector...
>
> EIGRP shares metrics (more or less) with IGRP, and the configuration
> commands are very similar. Otherwise, they are completely different
> protocols.
>
> >EIGRP behave`s like a link state protocol ......so it`s link state
>
> The only similarity between EIGRP and LS protocols are that they
> all use hello subprotocols and send changes only. That's a
>historical
> accident. There is absolutely no reason DV can't use change-only
> updates -- it's just the concept wasn't invented at the time RIP
> and IGRP were designed.
>
> >EIGRP is cisco`s own ...uses the best of both world`s ...so it`s a HYBRID
> >and should really have it`s own clssification....
> >
> >BUT
> >
> >according to the designer`s (i`m told) it IS a distance vector
> >protocol..With extensions
>
>
>Extensions only in the sense that OSPF and ISIS have had extensions
>over the years.
>
>DUAL was developed by JJ Garcia-Luna-Aceves while at Stanford
>Research Institute, now at University of California Santa Clara. He
>was not involved in Cisco's EIGRP implementation. His major area of
>research is distance vector protocols, and his formal papers on DUAL
>clearly identify it as a distance vector algorithm.
>http://www.cse.ucsc.edu/~jj/pubs.html
>
>Indeed, he hasn't stopped with DUAL. I've had conversations with him,
>and he definitely feels there are even faster DV algorithms than DUAL.
>
> From my book, "Designing Routing and Switching Architectures,"
>
>The original routing protocols were distance vector. They have
>continued to evolve. First-generation distance vector protocols, such
>as RIP, use periodic update (and may use triggered updates), loop
>detection through count to infinity, hop count metrics, and loop
>prevention through split horizon and holddown. Perhaps the most
>important distinction between the two generations is the way in which
>they use hop count. First-generation protocols use hop count for a
>wide range of functions, including metrics and loop detection.
>Second-generation protocols have more intelligent metrics and
>additional loop detection mechanisms.
>
>Second-generation distance vector protocols, such as IGRP, use a
>combination of periodic and triggered updates, loop detection by
>detecting increasing metric, complex metrics, and loop prevention
>through split horizon and holddown. Holddown can be turned off in
>most cases because the loop detection mechanism will allow only
>transient loops. Second-generation distance vector does not have a
>hello mechanism.
>
>Many courses and books are incorrect in the way they describe hello
>subprotocols, if they say that only link state protocols have hello
>mechanisms. Hello subprotocols are an alternative to using periodic
>updates as a keepalive mechanism, and have nothing to do with link
>state or distance vector. Historically, hello subprotocols first
>appeared in link state protocols, but that is a coincidence.
>
>
>...
>
>EIGRP is another evolutionary step in distance vector. Internally,
>EIGRP is a completely different protocol than IGRP. The only
>similarities are in the configuration commands and the metric
>computation. IGRP is upwardly compatible with EIGRP in the sense that
>EIGRP can accept routing updates sent to it by IGRP, not that the
>internal algorithms are at all similar. See "IGRP to EIGRP Migration"
>in Chapter 12, "Special and Hierarchical Routing Topologies."
>
>EIGRP's algorithm is called the diffusing update algorithm (DUAL). It
>was developed by J. J. Garcia-Luna at Stanford Research Institute.
>Garcia-Luna was not involved in Cisco's implementation of EIGRP.
>Several of the Cisco product architects have made strong arguments
>that properly designed distance vector algorithms have distinct
>technical superiority over link state. Link state partisans point to
>the evolution of their protocol family.
>
>
>EIGRP completely unloaded hop count and removed it from any role. It
>uses the same metric as IGRP, but has separate hello subprotocol and
>reliable update mechanisms that do away with most distance vector
>looping problems.
>
>In RIP and IGRP, loops are formed by old information. A significant
>reason that old information is propagated is the use of periodic
>updates. When the information distribution mechanism becomes
>change-only, there is no periodic updating with stale information. To
>have a change-only mechanisms, you need a hello subprotocol so you
>can detect dead routers. Until you can reliably detect dead routers,
>you cannot distinguish between not receiving an update because there
>has been no change, and not receiving an update because the router
>that would have sent it is down or unreachable.
>
>
> >
> >in the exam`s (lets keep this relevant to why were here ..and no i don`t
> >mean on the planet ....just the list)...it will be classified on the exam
>as
> >distance vector...
>
>
>I agree that Cisco exams will probably look for hybrid or enhanced
>distance vector.
>
> >
> >HTH....pppppplease don`t flame me.....Awww go on then ....if it makes you
> >happy
> >
> >steve
> >
> >
> >>From: "CCIE TB"
> >>Reply-To: "CCIE TB"
> >>To: [EMAIL PROTECTED]
> >>Subject: Is EIGRP a DV or LS protocol [7:10657]
> >>Date: Mon, 2 Jul 2001 12:02:38 -0400
> >>
> >>Hi Group members,
> >>
> >>Is EIGRP a Distance Vector or a Link State protocol. I thought it is a
>Link
> >>State until I read Cisco BSCN book, which classify it as both. Is that
> >>possible.
> >>
> > >Regards to all
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