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Browse Prior Art Database

T3 Delay Simulator

IP.com Disclosure Number: IPCOM000104597D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 106K

Publishing Venue

IBM

Related People

Sharma, V: AUTHOR

Abstract

Disclosed is a test tool to simulate city-to-city, cross-country propagation delays of common carrier T3, or satellite links.

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

T3 Delay Simulator

      Disclosed is a test tool to simulate city-to-city,
cross-country propagation delays of common carrier T3, or satellite
links.

      The simulator uses an IBM 3172 Interconnect Controller Model 2
platform and HSSI (high speed serial interface) or T3 adapters.

      Figs. 1.1, 1.2 and 1.3 illustrate a T3 link, a satellite link
and the use of a T3 Delay Simulator.

      The device simulates the delay caused by the transmission of
signals over large distances.  For example, assuming 4.92
microseconds/km for long haul fiber (about 0.70 times the speed of
light in free space), the following one-way propagation delays are
obtained.

     Terrestrial distance                    Approximate propagation
delay

     4830.9 km(3000 mi)                      24.0 milliseconds
     3220.6 km(2000 mi)                      16.0 milliseconds
     1610.3 km(1000 mi)                       8.0 milliseconds

      For one-hop satellite link transmission, the following
approximate one-way figures are assumed.

     Local earth station to Satellite 1      135.0 milliseconds

     Satellite 1 to Satellite 2              100.0 milliseconds
     (one hop)

     Satellite 2 to remote earth station     135.0 milliseconds

     Total (to nearest hundred)              400.0 milliseconds

      Minimum delays through the simulator are dependent upon actual
packet lengths and their incoming arrival rates as well as other
factors.  The simulator is not able to produce a delay smaller than
the minimum delay a packet must incur in being processed through the
simulator.

      The basic T3 link propagation delay simulator uses an IBM 3172
Interconnect Controller Model 2 with two HSSI adapters as shown in
Fig. 2.0.

      The packet transfer between the first and the second adapter
need not take place internally over the microchannel as shown in Fig.
2.0.  A pair of DSUs and appropriate cable assemblies can be used to
connect the first HSSI adapter to the second adapter externally,
thereby bypassing the internal microchannel bus.  Any protocol
exchange between HSSI adapters externally requires a pair of DSUs and
associated cable assemblies (Fig. 1.3).

The propagation delay simulator works as follows:

      When the simulator has received an incoming packet or a data
block onto its input HSSI adapter (last bit in), the processor on
this...