Browse Prior Art Database

Automatic Carrier Loss Detection for Ethernet

IP.com Disclosure Number: IPCOM000107525D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 1 page(s) / 52K

Publishing Venue

IBM

Related People

Bowcutt, R: AUTHOR [+3]

Abstract

A method for automatically detecting carrier loss on an idle Ethernet line is disclosed. The carrier loss state is detected by the data link control layer (DLC) of the communications protocol stack.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Automatic Carrier Loss Detection for Ethernet

       A method for automatically detecting carrier loss on an
idle Ethernet line is disclosed.  The carrier loss state is detected
by the data link control layer (DLC) of the communications protocol
stack.

      Ethernet adapters detect a carrier loss state by monitoring the
returned status when transmitting frames. However, this carrier loss
situation will not be detected if no frames are being sent.  For
example, if an application is idle or awaiting data, or if the
adapter is active but no application is active, the carrier loss
state cannot be detected.  Therefore, the Ethernet adapter can become
disconnected from the network with no notification of the problem for
long periods of time.

      In order to effectively detect the carrier loss state, frames
must be transmitted, as this is the only time that the adapter can
detect a carrier loss state.  The following is a software solution
and is implemented in the logical link control (LLC) protocol layer.

      The LLC layer monitors the transmit activity keeping track of
how long it has been since the last transmit attempt.  When this time
crosses a user-settable threshold, the LLC will automatically
transmit a frame to test for the carrier loss state.

      The frame that is transmitted by LLC is a test frame. The test
frame is sent to a unique diagnostic address, which is an Institute
of Electrical and Electronics Engineers (IEEE) globally defi...