Subject: A doubt in RFC 1974

From: "M.N.V.Suryanarayana" <[email-masked]>
Date: Tue, 10 Feb 1998 13:21:00 -0500 (EST)

Hi,

I'm a bit confused about the following statement in RFC 1974(PPP Stac LZS 
Compression Protocol, Page 12).

 "Receiver Process:
  If a CCP Reset-Request packet is received, the local compression engine 
  MUST be signaled that a Reset-Request has been received for the history
  number specified in the data field"

But RFC 1962(CCP) states that a Reset-Request is sent by the
Receiver(i.e the decompressor) to indicate a decompression failure. 
The transmitter sends a Reset-Ack after processing the Reset-Request.

I couldn't find in the RFC as to when a transmitter can send a Reset-Request.
When does a transmitter sends a Reset-Request packet to Receiver? 
When a Receiver process receives a  Reset-Request packet, its stated
that local compression engine MUST be signalled. What kind of action
needs to be taken by local compression engine?

Can someone please help me to understand this point better.

Thanks,
Ramachandran

---

From: James Carlson <[email-masked]>
Date: Tue, 10 Feb 1998 06:58:02 -0500

> The transmitter sends a Reset-Ack after processing the

Those are saying the same thing.  RFC 1974 just confusingly describes
it in passive voice from the view of the receiver of the message.  The
reset request always comes from the decompressor.  In other words,
when you get a reset-request on input, you have to reset your
compressor and send reset-ack.

(Note also that if you're doing 1974 in order to support Win95, that
it uses "mode 4," which is very different from the general 1974 text.)

> I couldn't find in the RFC as to when a transmitter can send a Reset-Request.

The decompressor transmits a reset-request to the compressor when it
detects an error (LCS, CRC, sequence, or algorithmic error).

"Transmitter" here isn't the same thing as "compressor."
"Transmitter" means the entity that transmits a packet.  Both the
compressor and the decompressor transmit packets in this sense.

> needs to be taken by local compression engine?

It resets itself.

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James Carlson, Consulting S/W Engineer  <[email-masked]>
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