Browse Prior Art Database

Method for Determining the Speed of an External Transmission Line

IP.com Disclosure Number: IPCOM000123227D
Original Publication Date: 1998-Jul-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Murray, C: AUTHOR

Abstract

Disclosed is a method for determining the external line speed for use by protocol stacks in the SS7 and X.25 protocol environment. This method is executed by software responsible for providing layer 1 and layer 2 assistance in these protocol stacks.

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

Method for Determining the Speed of an External Transmission Line

   Disclosed is a method for determining the external line
speed for use by protocol stacks in the SS7 and X.25 protocol
environment.  This method is executed by software responsible for
providing layer 1 and layer 2 assistance in these protocol stacks.

   Conventional methods use the DCE clock from the network
without knowing the clock rate at which data is being transmitted.
In many cases, to find the most efficient path to route data through
the network, the line speed of each link must be determined.

   The presently disclosed method for calculating the line
speed uses a software timer, provided by the kernel, which is
programmed as a one-second timer, and a hardware timer, provided by
the serial communications controller, which  is programmed to count
each bit time of the external clock.  The hardware timer is
programmed with an initial count of 0xfa00, to provide a count down
time corresponding to a transmission speed of 64000 kbps (kilobits
per second).  The hardware timer counts down from its initial count
to zero, interrupting the device driver and starting again at zero.
There is a software counter in the device driver interrupt handler to
record the number of times the hardware timer expires.  The software
timer interrupt handler causes the hardware timer to be stopped and
restarted every second, when an interrupt is received from the
software timer, with the count in the hardware timer when it is
stopped being used to calculate the external line speed.

   If the external line speed is le...