[113743] in North American Network Operators' Group
RE: IXP
daemon@ATHENA.MIT.EDU (Deepak Jain)
Mon Apr 20 17:55:47 2009
From: Deepak Jain <deepak@ai.net>
To: "Michael K. Smith - Adhost" <mksmith@adhost.com>, vijay gill
<vgill@vijaygill.com>, Jeff Young <young@jsyoung.net>, NickHilliard
<nick@foobar.org>, Paul Vixie <vixie@isc.org>, "nanog@merit.edu"
<nanog@merit.edu>
Date: Mon, 20 Apr 2009 17:54:58 -0400
In-Reply-To: <17838240D9A5544AAA5FF95F8D52031605EC0BA5@ad-exh01.adhost.lan>
Errors-To: nanog-bounces@nanog.org
>=20
> Hello Deepak:
>=20
> -----Original Message-----
>=20
> So here is an idea that I hope someone shoots down.
>=20
> We've been talking about pseudo-wires, and the high level of expertise
> a
> shared-fabric IXP needs
> to diagnose weird switch oddities, etc.
>=20
> As far as I can tell, the principal reason to use a shared fabric is to
> allow multiple connections to networks
> that may not justify their own dedicated ($$$$) router port. Once they
> do, they can move over to a PNI. However, an IXP is (at the hardware
> level at least) trying to achieve any-to-any connectivity without
> concern for capacity up to the port size of each port on every flow.
> Scaling this to multiple pieces of hardware has posed interesting
> challenges when the connection speed to participants is of the same
> order as the interconnection between IXP switches.
>=20
> So here is a hybrid idea, I'm not sure if It has been tried or
> seriously
> considered before.
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> Since the primary justification for a shared fabric is cost savings....
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> What if everyone who participated at an IXP brought their own switch.
> For argument's sake, a Nexus 5xxx. It has 20+ ports of L2, wire speed
> 10G.
>=20
>=20
> [Michael K. Smith - Adhost]
>=20
> This sounds like fertile ground for unintended consequences. Unmanaged
> spanning tree topological changes as three people, previously connected
> to their own switch and to others, now decide to connect to each other
> as well, using those inexpensive L2 ports.
If each port is in its own pVLAN or similar, and they are only allowed to t=
alk to their uplinks and not other L2 ports on the same switch, loops are a=
voided.=20
I should have hashed that point out with another line. Yes, strictly throwi=
ng up an unconfigured switch becomes a problem after the 2nd one goes in --=
but only for those brave enough to peer with you and dumb enough to allow =
their switch to behave that way. The double-edged clue sword.
Deepak
