This is one thing I bought up with Brent (for some reason it didn't get onto the
Page 48 of the Chorus NGA TUG states:
"Canonical Format Indicator (CFI) or Discard Eligible Indicator (DEI) is set to 0.
DEI applies to the 802.1ad outer tag and is not used, i.e. NGA is not colour-aware"
Brent said (off list in the past) that
" Yes, I spotted that this morning, hence we need some document updates - my
understanding (it's not my document) is that specific wording hung around from an old
version of the document and it was intended to point out that we will not utilise
DEI/colour marking from RSPs into our network."
From: nznog-bounces(a)list.waikato.ac.nz [mailto:email@example.com] On Behalf
Of Don Stokes
Sent: Thursday, 16 October 2014 11:53 a.m.
Subject: Re: [nznog] UFB Upload Issues
I thought the interface specs clearly say that they don't honour the DEI bit
(classification is done using the PCP bits) on ingress; while it doesn't say anything
about what colour the DEI bit will be on egress, I would have thought that the clear
implication is that DEI is not part of that specification.
Any RSP doing classification on it is therefore making an unwarranted assumption. I'd
be really surprised if anyone is actually doing so, but if you turned it off and it broke
something, that would be the RSP's problem, not yours. (Still, it's a fair
question to ask.)
The robust thing to do, given that the DEI bit behaviour is not defined, and given that
setting it has caused problems, is to treat DEI as a Must Be Zero field, ignore any
incorrectly set DEI bits on egress, and reliably set DEI=0 on egress. That both defines
the DEI behaviour and interoperates with pre 802.1Q-2011 compatible gear.
Otherwise, you really need to update the interface specification, with full consultation
with RSPs / TCF, to redefine the DEI bit behaviour. If you're going to do that, you
should revisit DEI behaviour on ingress as well to allow for (optional?) DEI colouring
instead of or as well as PCP colouring. I do think the ingress and egress behaviour should