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[nsp] relevance of ibgp in private mobile transit backbones?
Hi- a question that i hope is not too off topic for this list. The convention (to transmit BGP acquired routes cross network) is to use IBGP in transit nets. IBGP is chosen to spare the IGP-related complications caused by needing to carry large numbers of BGP routes if an IGP were used to do so , and not IBGP. If the scenario is one where 1) the number of BGP routes at each border gateway may be much lower than for the commercial internet 2)the transit network consists of relatively mobile nodes -thus making tcp meshes rather tricky to maintain- what scales (total no of routes across all border routers) is it worth considering an IGP such as OSPF to carry BGP routes across the transit net? thanks
Padma Krishnaswamy

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Re: [nsp] relevance of ibgp in private mobile transit backbones? [ In reply to ]
Please turn off HTML mail when posting to the list. It makes your message
very hard to read.

On Sun, 08 Sep 2002 18:19:18 +0000 padma krishnaswamy <kri234@hotmail.com> wrote:
> <DIV>a question that i hope is not too off topic for this list.</DIV>
> <DIV>The convention (to transmit BGP&nbsp; acquired routes cross
> network)&nbsp;is to use IBGP in transit nets. IBGP is chosen&nbsp;to
> spare the IGP-related complications caused by needing to carry large
> numbers of BGP routes if an IGP were used to do so , and not IBGP. </DIV>
> <DIV>If the scenario is one where </DIV>
> <DIV>1) the number of BGP routes at each border gateway may be much
> lower than for the commercial internet</DIV>
> <DIV>2)the transit network consists of relatively mobile nodes -thus
> making &nbsp;tcp meshes rather tricky to maintain-</DIV>
> <DIV>&nbsp;</DIV>
> <DIV>what scales (total no of routes across all border routers) is it
> worth considering an IGP such as OSPF to carry BGP routes across the
> transit net?</DIV>

I assume by "carry BGP routes across the transit net" you are talking about
non-border routers only and you will still run iBGP between AS border
routers? I don't think it would ever be worth using an IGP rather than BGP
between border routers these days.

How many routes are you talking about here? I woud not imagine any well
designed private network should have more than a couple of thousand routes
in it's BGP routing table - which any competant IGP should be able to
handle as external routes given enough memory. I do not think you would
have a problem unless you have a particularly messy IP allocation strategy
and can't aggregate much.

--
Ryan O'Connell
Mail: ryan@complicity.co.uk
CV: http://www.complicity.co.uk/ryancv.pdf
CCIE #8174
Re: [nsp] relevance of ibgp in private mobile transit backbones? [ In reply to ]
Sorry about the HTML. It's off now. and thanks much for the input- most
appreciated
regards

Padma


>From: Ryan O'Connell To: padma krishnaswamy , cisco-nsp@puck.nether.net
>Subject: Re: [nsp] relevance of ibgp in private mobile transit backbones?
>Date: Sun, 8 Sep 2002 20:22:35 +0100 (GMT Daylight Time)
>
>Please turn off HTML mail when posting to the list. It makes your message
>very hard to read.
>
>On Sun, 08 Sep 2002 18:19:18 +0000 padma krishnaswamy wrote: >
a question that i hope is not too off topic for this list.
> >
The convention (to transmit BGP acquired routes cross
> > network) is to use IBGP in transit nets. IBGP is chosen to > spare the
>IGP-related complications caused by needing to carry large > numbers of BGP
>routes if an IGP were used to do so , and not IBGP. >
If the scenario is one where
> >
1) the number of BGP routes at each border gateway may be much
> > lower than for the commercial internet
> >
2)the transit network consists of relatively mobile nodes -thus
> > making tcp meshes rather tricky to maintain-
> >

> >
what scales (total no of routes across all border routers) is it
> > worth considering an IGP such as OSPF to carry BGP routes across the >
>transit net?
>
>I assume by "carry BGP routes across the transit net" you are talking about
>non-border routers only and you will still run iBGP between AS border
>routers? I don't think it would ever be worth using an IGP rather than BGP
>between border routers these days.
>
>How many routes are you talking about here? I woud not imagine any well
>designed private network should have more than a couple of thousand routes
>in it's BGP routing table - which any competant IGP should be able to
>handle as external routes given enough memory. I do not think you would
>have a problem unless you have a particularly messy IP allocation strategy
>and can't aggregate much.
>
>--
>Ryan O'Connell Mail: ryan@complicity.co.uk CV:
>http://www.complicity.co.uk/ryancv.pdf CCIE #8174

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