Browse Prior Art Database

Method of Flow Control for 100-Mbps Ethernet Adapters

IP.com Disclosure Number: IPCOM000116079D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Amer, K: AUTHOR [+4]

Abstract

A method for minimizing received frame loss due to buffer overruns in a LAN station supporting one or more 100 Mbps half-duplex Ethernet adapters is disclosed. The 100 Mbps CSMA/CD Ethernet adapter uses an artificial collision to effectively block further transmission to the congested station.

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

Method of Flow Control for 100-Mbps Ethernet Adapters

      A method for minimizing received frame loss due to buffer
overruns in a LAN station supporting one or more 100 Mbps half-duplex
Ethernet adapters is disclosed.  The 100 Mbps CSMA/CD Ethernet
adapter uses an artificial collision to effectively block further
transmission to the congested station.

      100-Mbps Ethernet adapters installed in a LAN station may
overrun buffers because of inadequate system bus or CPU bandwidth and
thereby lose received frames.  The following solution avoids
expensive upper-layer protocol recovery of lost frames, since
Ethernet collisions do not get the upper-layer protocol involved.
The Ethernet MAC performs the recovery from collisions and
re-transmission with much lower delay.  The solution for temporary
over-capacity situations in 100-Mbps Ethernet attached workstations
is to artificially generate an Ethernet transmit signal (e.g., a
dummy frame) that will generate a collision state.  This solution
applies only to specific Ethernet configurations which are described
below.  The transmit signal and the resulting collision will
effectively block further transmission on the Ethernet by forcing
transmitting stations (including LAN switch ports) to back-off and
"hold" any queued frames.

      Disclosed here are two new methods for an Ethernet adapter to
generate a transmit signal.  The two methods are:
  1.  Decoding destination address as "my address" on an incoming
frame
       and a congestion condition exists in the workstation.  The
       transmit signal causes a collision to occur with the incoming
       frame.
      o  The "congestion condition" could be the condition of a
        receive FIFO in the adapter exceeding a preset threshold.  A
        receive FIFO exceeding a threshold would indicate a system
bus
        or CPU utilization level that would cause frame loss to
occur.
  2.  Detecting an incoming frame (i.e., receiving an Ethernet frame
       preamble).  The transmit signal causes a collision to occur
with
       the incoming...