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Re: [RPRWG] RE: [IPORPR] payload length and padding and stuff

Title:
Anoop/Necdet:
And the same could be true of maximum size as far as RPR MAC is concerned - although maximum size can be negotiated for mixed links using path MTU discovery (rfc1191) protocol at L3. In general, I don't think RPR should preclude use of mixed media, as long as there is an external logic for rate-matching (how? - PHY people can possibly advise on it). RPR MAC wouldn't even know the difference.
=Pankaj

Necdet Uzun wrote:
Anoop,

Another thing to note that RPR over Ethernet does not require padding of
RPR frames as we do not have the same 64 byte minimum packet size
requirement as Ethernet.

Thanks.

Necdet

Anoop Ghanwani wrote:

  
Frank,

We shouldn't be trying to mix different PHYs,
e.g. 10GE and OC-192, since they are in fact running
at different data rates, and having PHYs with different
data rates on the same ring is not allowed by the
current version of the draft.  I think the draft
is silent on this specific issue, though.

I'm cc.-ing the 802.17 list since this is an interesting
issue that has come up there as well.  Maybe someone
else might be able to shed some light on this
(PHY people??).

-Anoop

    
-----Original Message-----
From: Frank Kastenholz [mailto:fkastenholz@xxxxxxxxxxx]
Sent: Tuesday, December 03, 2002 3:46 PM
To: iporpr@xxxxxxxx
Subject: [IPORPR] payload length and padding and stuff


i'm editing the iporpr document and have come across a question...

suppose i have an 802.17 ring comprised of both gig-e and sonet
sections. gig-e, i assume, has the usual ethernet min frame
size rules, so if a dataframe is transmitted onto gig-e and
the payload is too short, it gets padded so that the frame
is 64 bytes. if a frame is transmitted onto a sonet section,
no such padding is needed, since there are no min frame length
rules for sonet. so what happens when a frame that was initially
transmitted on a sonet section reaches a gig-e section of
the ring:

      +-----------+      +-----------+       +-----------+
      | Station 1 |      | Station 2 |       | Station 3 |
      +-----------+      +-----------+       +-----------+
       /        \          /        \          /        \
...___/          \________/          \________/          \___...
                   sonet                gig-e

A frame generated at station-1 that has, let's say, only a 20 byte
payload, would be 42 bytes long. This is fine for sonet. What
happens when the frame reaches the gig-e section between stations 2
and 3?
- is the frame padded by the mac/phy layers in station 2?
- is the frame dropped?
- are the min-frame rules dropped for gig-e when it's being used
  for .17?
- is it illegal to mix sonet and gig-e in the same ring?
- am i very confused and is the answer obvious to all but me?

thanks

frank kastenholz