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Non-Disruptive Physical Route Switching

IP.com Disclosure Number: IPCOM000119641D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 5 page(s) / 158K

Publishing Venue

IBM

Related People

Bigo, F: AUTHOR [+3]

Abstract

The purpose of this article is to propose a solution based on modems offering a data multiplex feature and on the functions which are offered by the SNA (System Network Architecture) Communication Controllers. The association of this type of modem and of the Communication Controllers allows switching the traffic to a back-up route in the case of link failures. With such a solution, Communication Controllers will not "see" any line failures and will not see any modem failures as well.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 44% of the total text.

Non-Disruptive Physical Route Switching

      The purpose of this article is to propose a solution
based on modems offering a data multiplex feature and on the
functions which are offered by the SNA (System Network Architecture)
Communication Controllers. The association of this type of modem and
of the Communication Controllers allows switching the traffic to a
back-up route in the case of link failures. With such a solution,
Communication Controllers will not "see" any line failures and will
not see any modem failures as well.

      Description Fig. 1 illustrates a Delta Network. The proposal is
not limited to a Delta network and can be generalized but it makes it
simpler to present it in such an environment.
 There are 3 Communication Controllers referenced: A, B and C.
      There are 6 modems referenced Ab, Ac, Ba, Bc, Ca, Cb.

      Modems Ab and Ba are linked through a telephone line;
similarly, modems Bc and Cb and modems Ac and Ca are linked.

      The modems are 9600 bps modems and equiped with a data
multiplex feature (Note: the bit rate is irrelevant and 9600 bps is
used for ease of writing and reading.  The same comment applies to
the bit rate defined hereunder for each port of the modem).

      1.  Case 1 (Fig. 1):
      Controllers A and B need to be connected to each other.
      Controllers A and C need to be connected to each other.
      Controllers B and C do not need to be logically connected.

      Controller A is linked to Controller B using a Transmission
Group (TG) of 2 links. A TG is an SNA single logical route
implemented on several physical links or paths which are in parallel
and all in use and active at the same time.

      The first link of the TG is attached to modem Ab and Ba using
a bit rate at 7200 bps.

      The second link is attached to modem Ac and Bc while the
corresponding ports on Modem Ca and Cb are connected back to back
(like tail modems). This link works at 2400 bps.

      So, to summarize, the TG between Controllers A and B goes as
follows:
      - the first link goes at 7200 bps directly between the two
controllers.
      - the second link goes at 2400 bps through the local modems of
controller C.

      The other TG between Controllers A and C is established using
the same concept as the one described above.

      It results that Controller A has two TGs and each TG is made of
two links: one at 7200 bps and the other one at 2400 bps.

      Modem Ab, Ac, Ba, Ca each have a port at 7200 bps and one
at 2400 bps.
      Modem Bc and Cb each have 2 ports at 2400 bps.

      Note: The example taken for the data multiplex is made of 7200
and 2400 bps ports for a total aggregate of 9600 bps. We could as
well have taken 4800 bps/4800 bps.

      2.  Case 2 (Fig. 2):
      This case is similar to case 1 with the addition of one TG to
logically connect Controller C and B.

      Case 2 makes th...