RE: payload length and padding and stuff

The min frame requirement of Ethernet is not carried into RPR. (This is baggage left over from Ethernet's CSMA/CD days that is no longer used.) Also agreed at the last meeting is that any PHY that does require a min length must implement padding and unpadding in its reconciliation sublayer (RS) so as not to effect other links running other PHYs.

John Lemon

-----Original Message-----
From: Frank Kastenholz [mailto:[email protected]]
Sent: Tuesday, December 03, 2002 3:46 PM
To: [email protected]
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
_______________________________________________
IPORPR mailing list
[email protected]
https://www1.ietf.org/mailman/listinfo/iporpr