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