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IS-IS,why would you use this vs. others

 
 
wysiwyg21
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      02-01-2005
Just reading about IS-IS it appears to have limitations that other
routing protocols don't have. In configurations over NBMA frame relay
or dealing with suboptimal routes because of its static metric it does
not appear to have the flexibility or richness that OSPF does. So, what
are IS-IS benefits vs. the other protocols? I've read that IS-IS is
used by ISPs. Why do they use it instead of others?

 
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John Osmon
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      02-02-2005
wysiwyg21 <(E-Mail Removed)> wrote:
: Just reading about IS-IS it appears to have limitations that other
: routing protocols don't have. In configurations over NBMA frame relay
: or dealing with suboptimal routes because of its static metric it does
: not appear to have the flexibility or richness that OSPF does. So, what
: are IS-IS benefits vs. the other protocols? I've read that IS-IS is
: used by ISPs. Why do they use it instead of others?

For the most part, the choice between IS-IS and OSPF comes down to
personal preference. I like IS-IS because it is *built* to carry metrics
for protocols other than IPv4 (e.g. IPv6). Other people like OSPF
becuase it runs over IPv4.

Also, there are a number of useful pieces of equipment that will
never speak IS-IS -- so OSPF might be the only choice available
under certain circumstances.

A good presentation on the subject can be found at:
http://www.nanog.org/mtg-0006/katz.html
 
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Ben
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      02-02-2005
John Osmon wrote:
> wysiwyg21 <(E-Mail Removed)> wrote:
> : Just reading about IS-IS it appears to have limitations that other
> : routing protocols don't have. In configurations over NBMA frame relay
> : or dealing with suboptimal routes because of its static metric it does
> : not appear to have the flexibility or richness that OSPF does. So, what
> : are IS-IS benefits vs. the other protocols? I've read that IS-IS is
> : used by ISPs. Why do they use it instead of others?
>
> For the most part, the choice between IS-IS and OSPF comes down to
> personal preference. I like IS-IS because it is *built* to carry metrics
> for protocols other than IPv4 (e.g. IPv6). Other people like OSPF
> becuase it runs over IPv4.
>
> Also, there are a number of useful pieces of equipment that will
> never speak IS-IS -- so OSPF might be the only choice available
> under certain circumstances.
>
> A good presentation on the subject can be found at:
> http://www.nanog.org/mtg-0006/katz.html

great link
 
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Stephan
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      02-02-2005
If you look at IS-IS vs. OSPF, than you will see that...



- IS-IS is more flexible when extending the backbone.

- IS-IS supports OSI and TCP/IP

- IS-IS is more extensible through TLV (type, length, value) design



Regards

Stephan


 
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Vincent C Jones
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      02-03-2005
In article <(E-Mail Removed) .com>,
wysiwyg21 <(E-Mail Removed)> wrote:
>Just reading about IS-IS it appears to have limitations that other
>routing protocols don't have. In configurations over NBMA frame relay
>or dealing with suboptimal routes because of its static metric it does
>not appear to have the flexibility or richness that OSPF does. So, what
>are IS-IS benefits vs. the other protocols? I've read that IS-IS is
>used by ISPs. Why do they use it instead of others?


Every routing protocol makes trade offs, which means that each has
its strengths and weaknesses. None are ideal for all applications.

As for why IS-IS in ISPs, two factors which had a major influence
at the time but no longer apply: IS-IS was available, stable,
and functional years before OSPF could be trusted; and IS-IS could
also be used to route OSI CLNS, which was considered a requirement
for a while. If and when IPv6 routing becomes an issue, it will
be interesting to see if history repeats itself, given that IS-IS
merely needs a few minor tweaks to add IPv6 support to existing
structures while OSPF is so IPv4 optimized it will need a rewrite.

--
Vincent C Jones, Consultant Expert advice and a helping hand
Networking Unlimited, Inc. for those who want to manage and
Tenafly, NJ Phone: 201 568-7810 control their networking destiny
http://www.networkingunlimited.com
 
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