Browse Prior Art Database

I/O Marker Chaining

IP.com Disclosure Number: IPCOM000111029D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 86K

Publishing Venue

IBM

Related People

Sachs, MW: AUTHOR

Abstract

Some I/O data streams consist of two or more logically distinct segments of variable length. An example is the Internet Protocol (IP) packet which has a variable length header and a variable length payload. Performance of the receiving system can be improved if the segments of the data stream can be read into separate buffers in processor memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

I/O Marker Chaining

      Some I/O data streams consist of two or more logically distinct
segments of variable length.  An example is the Internet Protocol
(IP) packet which has a variable length header and a variable length
payload.  Performance of the receiving system can be improved if the
segments of the data stream can be read into separate buffers in
processor memory.

      Current I/O architectures do not provide an efficient means of
directing variable length segments of a data stream into separate
input buffers.  For example, in the IBM ESA/390* I/O Architecture,
the program supplies fixed length buffers and there are two ways of
chaining the buffers.  In data chaining, the first buffer is filled
completely before the data start entering the second buffer.  Command
chaining provides variable length segments but requires multiple
handshakes across the link, with processing of control information
(e.g. status for the old command, exchange of command frame and
command-response frame for the new command) before the data start
flowing into the second buffer.  This is too much overhead for
splitting a single data stream, especially with Gbit/sec link speeds.
Means are required to direct variable length segments of a data
stream into separate buffers without the overhead of treating each
segment as a separate I/O operation.

      The invention disclosed herein provides a new type of I/O
buffer chaining called Marker Chaining.  Marker Chaining is a means
to direct each variable length segment of a data stream into a
separate input buffer based on a marker in the data stream.  The
marker is a simple indication which does not involve handshaking
across the link or processing of complex control information.  A
marker can be a control bit, a special delimiter on a data frame, a
change in the value of a numerical control field in a data frame, or
any similar indicator.  For the proposed ANSI Fiber Channel Standard,
natural markers are Sequence boundaries or a change in the value of
the Information Category field.  In the case of using Internet
Protocol on Fiber Channel Standard, the IP packet header could be
sent as one Sequence and the packet payload could be sent as a
separate Sequence.  At the recipient ...