Browse Prior Art Database

Keep-Alive Redundancy and Back-Up for T3 and E3/E2/J2 Lines

IP.com Disclosure Number: IPCOM000114758D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Suffern, ES: AUTHOR [+2]

Abstract

Because of the high cost to attach to a high-speed communication line in the US or Europe, a redundant adapter with back-up capability must be provided to the customer as an alternative to buying two high-speed communication lines. Currently, redundancy exists for low-speed lines. However, different problems are encountered when backing-up high-speed lines. The line compensation network on the high-speed Line Interface Card (LIC) must be able to compensate for the addition of a "Y" cable. Second, a keep-alive scenario must be defined between the adapter and the LIC to ensure the failing element can be eliminated and data transmission and reception can continue.

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Keep-Alive Redundancy and Back-Up for T3 and E3/E2/J2 Lines

      Because of the high cost to attach to a high-speed
communication line in the US or Europe, a redundant adapter with
back-up capability must be provided to the customer as an alternative
to buying two high-speed communication lines.  Currently, redundancy
exists for low-speed lines.  However, different problems are
encountered when backing-up high-speed lines.  The line compensation
network on the high-speed Line Interface Card (LIC) must be able to
compensate for the addition of a "Y" cable.  Second, a keep-alive
scenario must be defined between the adapter and the LIC to ensure
the failing element can be eliminated and data transmission and
reception can continue.

      To provide this feature for the customer's high-speed lines
(Figure), the line compensation circuitry has been designed to ensure
that all transmission parameters are within specifications with the
addition of a "Y" cable.  The addition of the "Y" cable permits the
actual switch-over to occur in the case of LIC failure.  The addition
of a keep-alive message sequence has been defined to ensure the
adapters are operational and detect when either one fails.

      To ensure both the adapter and its connected LIC are
operational the adapter and internal LIC have defined a keep-alive
sequence.  The keep-alive message sequence is enabled by the adapter,
is initiated by the adapter every 1 millisecond ( 10
microseconds), and then sent to the internal LIC.  When the LIC
receives this message, it must respond with a keep-alive acknowledge
message of its own within 1 millisecond ( 10 microseconds).  These
values can be modified after the start of the keep-alive sequence in
increments of 500 microseconds.

      In case of a failure in the LIC in the primary path, the
adapter can issue a command to the LIC and cause it to disconnect
from the communication line.  The stand-by LIC can then be switched
to operational mode and become the primary path.  This switching can
be accomplished only if the adapter is able to send the switch-over
command to the failing LIC and the LIC can receive it.  This cannot
always be guaranteed in the case o...