RE: Comments ......

["Barry Raveendran Greene" <bgreene@cisco.com>]

Hello Everyone,

Rob just added me to the list. Looks like I missed some messages to put this
into complete context.

On the general topic of L3 (a router is the IXP medium) or a L2 (a switch is
the IXP Medium) type of IXP - then I vote with L2. In fact, I do not
consider a L3 IXP - with a router as the IXP medium - as a viable IXP model
anymore. So in this light, what Randy is saying is true.

In fact, I do not know of ANY IXP on the planet that is a "Router" (i.e. the
original CIX design). Those that are "routers" are not IXPs - they are
transit services with "IX" added as a marketing ploy.

Any ISPs who wants to gain the benefit of an IXP _must_ be willing to
co-locate their own router on the IXP. There are a variety of reasons
(business, technical, security, policy, etc). If you need all the reasons
written down, let me know and I'll document them.

Putting a router on the IXP so other ISPs can get a lease line into it (i.e.
a L3 on top of a L2) is something I do not recommend. It changes the IXP
into a pseudo transit service. The IXPs that have gone down this path
eventually turn into transit services (Taiwan's IXPs come to mind). Yes, it
appears to be "helpful" to those ISPs who cannot afford a router, but the
track record for keeping the IXP an IXP (and not a transit service) is
bleak.

Also - excuses on "the router is too expensive" are eliminate when you build
an ethernet based IXP with a Route Server (RS) or Route Reflector (RR). This
is how you get routers as small as Cisco 1600Ms on an IXP - they peer with
the RS or RR.

BTW - there are three modes of ethernet based IXPs:

+ Meshed Peering
+ Route Reflector Based Peering
+ Router Server Based Peering

Meshed and RS are the most common on the IXPs in the world. RR based IXPs
are places where the IXP is working to keep their initial capital cost low.

My recommendation for an IXP like in Uganda would to allow Meshed + RS or
Meshed + RR.

-> Route Servers require a Unix box. They will allow the small ISPs with
little router (i.e. like the Cisco 1600M) to peer at the IXP along side big
ISPs who just peer with the Meshed peering technique. The expense excuse for
RSs are gone - Abha Ahuja is going to help expand the section in my IXP
whitepaper to show how a RS impimented at a small IXP.

-> Route Reflectors require also require a Unix Box with Gated or a router
supporting BGP RR. They also allow the little guys to peer with the big
guys. The big disadvantage of a RR is that is requires a AS number for the
IXP and adds an AS number to the BGP path. We - Cisco - may put in a knob to
change the extra hop issues. We've not decided if it is worth the risk of
customers screwing up their networks by turning it on where it should not be
turned on. The new documentation on a low cost Route Server example might
eliminate the need for RR based IXPs. So we're going down that path before
tweaking the BGP code.

In summary - keep away from ISPs connecting lease lines into an "IXP Router"
on the IXP. It has never proved to scale or survive as a "IXP." Ethernet
Switch based IXPs are the way to go. Meshed with a Route Server or a Route
Reflector allows the small players with small routers to interconnect with
the big players.

If you can afford the Unix box - I would go with a L2 IXP with a Route
Server. The new documentation that Abha and I are going to help write will
give you a step by step template on how to make it happen.

Barry

PS - Abha will be at AFNOG - so people going can pick her brains.





> -----Original Message-----
> From: owner-techies@alpha.eahd.or.ug
> [mailto:owner-techies@alpha.eahd.or.ug]On Behalf Of Randy Bush
> Sent: Thursday, May 03, 2001 3:10 PM
> To: Lunghabo James
> Cc: techies@uixp.co.ug
> Subject: Re: Comments ......
>
>
> >> It seems to me like the simple setup is actually the better one in this
> >> case from arguments put forward.
> > Why ?
>
> was covered in previous mail, but
>   o it is simpler
>   o it is less costly
>   o it is more reliable
>   o it takes less maintenance by the ix staff
>   o it technically works better as it does not add cruft to the bgp
>     and bgp paths
>   o it allows bi-lateral peering as well as multi-lateral
>
> and for all the above and more, all the exchange points in
> europe, asia, the
> states, ... use it.  only a few folk in isolated areas have been suckered
> into the layer 3 tech-nocolianist dependence on a router vendor.
>
> randy
>

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