[176199] in North American Network Operators' Group
RE: Overlay as a link
daemon@ATHENA.MIT.EDU (Phil Bedard)
Wed Nov 19 11:17:40 2014
X-Original-To: nanog@nanog.org
To: Glen Kent <glen.kent@gmail.com>, "nanog@nanog.org" <nanog@nanog.org>
From: Phil Bedard <bedard.phil@gmail.com>
Date: Wed, 19 Nov 2014 11:17:20 -0500
In-Reply-To: <CAPLq3UP0-Bx6zBqLOtWymbXqAhAYJQbAk1q=eB=f+_LcZoqDEQ@mail.gmail.com>
Errors-To: nanog-bounces@nanog.org
There are certain protocols and mechanisms tied to a physical medium or MAC=
layer. If you are doing L3 tunneling you lose those options, if you are d=
oing L2 tunneling you may lose less of them depending how transparent the t=
unnel is.=20
Things like Ethernet pause frames or 802.3ah instead of BFD. So from a c=
ertain layer like L3+ it looks and behaves like a physical link but there a=
re differences. =20
Phil
-----Original Message-----
From: "Glen Kent" <glen.kent@gmail.com>
Sent: =E2=80=8E11/=E2=80=8E19/=E2=80=8E2014 2:04 AM
To: "nanog@nanog.org" <nanog@nanog.org>
Subject: Overlay as a link
Hi,
When youre doing overlay networking, i.e., you have tunnels from one
virtual machine in a DC to another in another DC, then can i consider a
tunnel between the two virtual machines as a "physical link" that exists in
a regular network?
I am wondering on what possibly can be the difference between a tunnel
being considered as a link and a true physical link.
I could run routing algorithms on both. The tunnel would only be considered
as an interface. Or i could run BFD on both.
Once difference that i can think of is that while you can send multiple
frames together on a tunnel (for example if there are ECMP paths within the
tunnel), you may not be able to send multiple frames at the same time on a
physical link. Anything else?
Glen
