Browse Prior Art Database

Cell Structure for Frame Segmentation and Re-assembly at Several Gigabits Per Second

IP.com Disclosure Number: IPCOM000107188D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 3 page(s) / 93K

Publishing Venue

IBM

Related People

Luijten, R: AUTHOR

Abstract

This cell structure facilitates the segmentation of variable-size frames into small, fixed-size cells at speeds of gigabits per second. Novel is the use of fixed-size and fixed-position fields within the cell. (Image Omitted)

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

Cell Structure for Frame Segmentation and Re-assembly at Several Gigabits Per Second

       This cell structure facilitates the segmentation of
variable-size frames into small, fixed-size cells at speeds of
gigabits per second.  Novel is the use of fixed-size and
fixed-position fields within the cell.

                            (Image Omitted)

      A cell is the unit of data consisting of a header and payload
that is switched through fast packet switches.  A cell is typically
small in size (between 32 and 64 bytes) and of fixed size.  A frame
is variable in size (between 1 byte and several tens of kilobytes)
and contains the data that is exchanged between users of a switching
network.

      Adapters between the users and the packet switch perform the
segmentation and re-assembly function to go from frames to cells and
back to frames again.

      The present cell structure facilitates the following:
1.  Structure that allows segmentation and re-assembly functions to
be performed in hardware at speeds of several gigabits/second.
2.  Low latency: The frame size needs not to be known before the
first cell of a frame can be transmitted. This also reduces the
required memory size on the adapter.
3.  The separation of control and data cells is facilitated by simple
decoding.  The idea is that data cells are dealt with in hardware,
while control cells  - which by nature are low-bandwidth traffic -
are dealt with by software.
4.  The supporting of scalable architecture by allowing different bus
sizes for the adapter.

      A frame is segmented into a First cell, zero or more Middle
cells and a Last cell.  If a frame is shorter than one cell, then it
is sent with an Only cell.

      The first point is achieved by using fixed-size and
fixed-position fields across all possible cell types.  The second
point is achieved by not requi...