ADC 
Kentrox

ATM Testing -- ADC Kentrox

George Kuroda

Rolf Hahn

ADC Kentrox

Table of Contents

Stan Barber's Notes

Problem that are specific to Kentrox equipment and other problems. There have been three problems discovered and have been corrected. There are two other problems that are not Kentrox-specific.

Kentrox -- Rolf Hahn

Three symptoms
  1. Packet discard of interleaved AAL5 packets with CRC error indication
    Cause: Faulty CRC IC timing
    Fix: Corrected the timing relations and replaced an IC.
  2. Packets loss with running the "Dual Ping" test.
    Cause: Problem with reassumebl buffer management that caused on one reassembly machine (instead of 16) to be avilable under this test's conditions.
    Fix: Modified the reassumble buffer management circuitry to eliminate the problem. Two ICs replaced.
  3. Error on the HSSI port from the ADSU to the Router
    Cause: Impendence mismatch of cable to drivers due to manual modifications of units in test.
    Fix: Standard production units with new board layout are not shipping.

Kentrox -- George Shenoda

Other Issues

Running both HSSI and DS-3 (UNI) at the same clock rate creates a situation of throughput mismatch between the two rs due to ATM overhead exceeding frame overhead.

This problem means that the HSSI should be clocked at 34mb/sec if the DS-3 is clocked at 45mb/sec.

What about clocking the HSSI at a slower rate and clocking the DS-3 at a high rate for a "poor-man's rate shaping"? Not in the current product, but it is being planned. Kentrox does not plan to make this dynamic. The crowd would like this, though.

When the data is coming from the ATM network to the HSSI, how many reassembly buffers are needed? There is no evidence that more than 16 are needed. However, Kentrox will have more in a future product.

Immediate Enhancements: User Selectable clock rate on the HSSI in 1Mbps Increments. Transmit and receive clocks will be independent. This will enable the user to limit the total traffic to and from the network. It will be available in April 1995. The maximum clock rate will be 45Mb/sec, but someone suggested 51 Mb/sec should be considered since HSSI can run that fast. Rolf suggested that Kentrox could do 50 Mb/sec. Currently, the box will support telnet connections to find out the stats on the box. Guy Almes suggested they should make buffer paramenters of the packet reassembly unit available via SNMP. There is no MIB defined for this, but it could be in a proprietary/enterprise MIB.

Future followup

Traffic policing per virtual connection 32 concurrent reassumbly machines up to 9232 Octets.

A modular product will be announced next month whichi will allow mix and match of various interfaces and will be available at the end of the year.


Copyright © 1995 Stan Barber. Reproduction with attribution granted.
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