RE: payload length and padding and stuff

Frank,

.17 specifies homogeneous rings. Mixed phys and different speeds on spans
and ringlets are disallowed. As for the frame size, there has been some
discussion on this topic and there will probably need to be a phy dependent
frame size requirements. For now, this is a configurable parameter. 

Also, no padding is specified by the .17 MAC for frames in transit. Whether
there needs to be padding by the MAC for transmitted frames is still open.

Hope this helps.

Nader Vijeh

-----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
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