SDP Mail Archive: SDP> Re: SDP, IPP>PRO Proposal for TIPSI-like protocol

SDP> Re: SDP, IPP>PRO Proposal for TIPSI-like protocol

Harry Lewis (
Wed, 6 May 1998 19:52:15 -0400

One thing it would buy is a simpler (than 1284.4) way to flow IPP over =
parallel - no? Isn't this basically what Lexmark has found? I'm confuse=
d why
TIPSI has a packet structure, Lexmark was shipping it on parallel and t=
hen .4
was invented - maybe some background could help (I always thought it wa=
s to
flow SNMP over parallel ;-). If it's true that the .1 packet is only st=
there for legacy I might buy Bob's argument. But I suspect .4 is a much=
complex implementation.

Bob, doesn't your proposal say we would have to invent a transport (if =
already there) to "IPize" every physical layer (ex. serial)?

Harry Lewis - IBM Printing Systems on 05/06/98 05:32:34 PM
Please respond to
Subject: SDP, IPP>PRO Proposal for TIPSI-like protocol

I just finished scanning IEEE 1284.3 and IEEE1284.4. The most interest=
part is Chapter 8 "Service Provider Interface (SPI)" in IEEE 1284.4. T=
chapter describes a "Berkeley Sockets-compatible interface for clients =
servers to access the services provided by 1284.4".

So if I understand the intent of 1284.4, it is to provide a layer that
supports sockets over parallel connections. All we need to do in IPP is=

reference sockets for TCP/IP and 1284.4 and we don't have to worry abou=
t the
issues at that layer.

So, I conclude that we don't need to packetize IPP or do much of what i=
proposed in Roger and Harry's paper. Instead, we can send IPP directly =
sockets layered on top of TCP/IP or 1284.4. There are a few easy-to-so=
issues, such as chunking for document data and intermediate acknowledge=
when attributes are verified for PrintJob. But otherwise IPP stays as i=

If you disagree with my conclusions, I would like to know what the
TIPSI-like packetizing layer provides that sockets don't also provide?

Bob Herriot