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Voice packet Jitter distribution in complex meshed network

IP.com Disclosure Number: IPCOM000185039D
Original Publication Date: 2009-Jul-08
Included in the Prior Art Database: 2009-Jul-08
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Abstract

This disclosure address transmission of packets which must be delivered in respect with a maximum delay in a complex meshed network (Voice/Audio/Video packets).

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Voice packet Jitter distribution in complex meshed network

PROBLEM TO BE SOLVED

This disclosure address transmission of packets which must be delivered in respect with a maximum delay in a complex meshed network (Voice/Audio/Video packets)

- Delay for packet transmission is related to 3 Factors:
- Packet Length
- Waiting time in transmit queue
- Route used in the network
- Lines speed for a route linking the source and target elements are fixed.
- Waiting time in transmit queue is variable according to the traffic.

All these factors results in a variable delay between the transmit and reception side called « Jitter ».
- Jitter is generally absorbed using a Leaky bucket
In a leaky bucket, the packets arrive with variable delay, but are delivered with fixed delay. The maximum number of packets in the leaky bucket defines the buffering time and the maximum admissible jitter. An empty leaky bucket due to an out of specification jitter leads to an under run and the next packet received will be discarded as it will arrive after delivery time.

As a result, the problem to be solved is to minimise the overall jitter.

PRINCIPLE OF THE SOLUTION

The principle is to put alternatively the packet at the front or the end of the transmitting queue.

- Each voice packet has a Priority bit.
- If the priority bit is set to "True" then the packet is put in front of queue and the Priority bit is turned to "False".
- If the priority bit is set to "False" then the packet is put at the end of queue and Priority bit is turned to "True", but if the queue packet count is lower than a predetermined threshold, then the Priority bit is not changed and remains "False"

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SOLUTION DESCRIPTION

- At system start 200, some variables are initialised 205...