Use the search string "isis" ( no dash )
>From my own limited studies:
IS-IS tends to treat level-1 areas as stub networks - therefore smaller
routing tables
IS-IS sure looks a lot chattier than OSPF. Debug ISIS adjacency reveals a
LOT of traffic generated just by the protocol keepalives
The killer in OSPF is the SPF algorithm, and the related processor intensive
activity It has less to do with size of routing tables.
IS-IS tends to be more efficient than Ospf in that it is not beholden to the
area 0 concept and the necessity for all inter area traffic to go through
area 0.
BTW, I have been told by folks who work in really big networks that none of
the routing protocols scale beyond 4-5K routers. As an interesting aside, a
few weeks ago on NANOG there was a discussion about the largest RIPv1
network in existence. It was revealed that until a year or two ago, Xerox
used RIPv1 and had a few thousand routers running RIPv1 on the network.
I'm sure someone will correct any of my mistaken impressions.
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Curtis Rose
Sent: Sunday, May 20, 2001 9:36 PM
To: [EMAIL PROTECTED]
Subject: Re: How is IS-IS more scalable than OSPF? [7:5207]
I still can not leave that question alone. It is a good question. Why is
IS-IS for large networks? The why is the key.
http://www.juniper.net/techcenter/techpapers/200003-02.html
.Design for Scalability
Scalability is concerned with the ability of the implementation to grow with
the ever-expanding network environment. There are a number of factors that
play a key role in determining the scalability of a routing protocol
implementation:
' Maximum number of interfaces supported
' Speed of a routing table search
' Maximum number of routes that can be stored in the routing table
' Maximum number of OSPF or IS-IS adjacencies or BGP peers that can be
supported on each router
' Maximum number of OSPF LSAs or IS-IS LSPs that can be stored in the
router's link-state database
' Ability of the policy control language to permit administrators to easily
and efficiently control the import, export, and modification of an enormous
amount of routing information
http://www.nortelnetworks.com/index.html
Type IS-IS and they have a great PDF on the protocol.
http://www-search.cisco.com/pcgi-bin/search/public.pl?q=OSPF+vs+IS-IS&num=10
&searchselector=0 My search on Cisco
I noticed Cisco will compare OSPF with RIP or EIGRP but not IS-IS I wonder
why??
I can not find anything on IS-IS perhaps I am not using the correct string
when looking on Cisco.. I notice with Nortel and Juniper I had no issues
finding something on it.
Curtis
----- Original Message -----
From: "Curtis Rose"
To:
Sent: Sunday, May 20, 2001 11:20 PM
Subject: Re: How is IS-IS more scalable than OSPF? [7:5207]
> Good Question!
>
> I have read that IS-IS can accept more nodes than OSPF. Yet, I find that
> Juniper is pushing IS-IS and the US Govt has some networks on IS-IS.
Black
> in the IP Routing Protocols basically states it is an IP Protocol but is
not
> used in the internet or much elsewhere for that matter.
>
> In Priscilla's Top-Down Network Design book on page 236 shows the
> scalability of OSPF to about 50 routers per area and about 100 areas and
> the IS-IS 1,000s of routers.
>
> In Sam Halabi's book Internet Routing Architectures on page 100
.....Today,
> both IS-IS and OSPF are widely deployed in ISP Networks. The maturity and
> stability of IS-IS has resulted in it remaining deployed in large
networks,
> as well as its being the IGP of choice for some recently deployed
networks.
>
> In Catherine Paquet and Diane Teare's book Building Scalable Cisco
Networks
> on page 23 is a Table comparing OSPF, IS-IS and EIGRP. Basically IS-IS
wins
> out for Scalability.
>
> Sorry I can not be of more help.
>
> Curtis
>
> Curtis Rose
> ----- Original Message -----
> From: "NRF"
> To:
> Sent: Sunday, May 20, 2001 10:24 PM
> Subject: How is IS-IS more scalable than OSPF? [7:5207]
>
>
> > Hello
> >
> > Several people have asserted that IS-IS (for IP) has demonstrated more
> > scalability than OSPF. What accounts for this? I have heard that it
has
> > to do with IS-IS being able to take advantage of Partial-route Updates
> when
> > IP information changes, as opposed to running Dijkstra all the time, is
> that
> > the only factor, or are there other reasons?
> >
> > Thanx
> > FAQ, list archives, and subscription info:
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