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Delay-Guaranteed Service for Store-And-Forward Networks

IP.com Disclosure Number: IPCOM000047300D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 5 page(s) / 50K

Publishing Venue

IBM

Related People

Kermani, P: AUTHOR

Abstract

This control procedure guarantees a maximum end-to-end delay per session for data communication traffic within a designated service class in a store-and-forward network having virtual circuits and fixed routing. At each node in the network the procedure limits the number of active sessions which can be accepted into the delay-guaranteed service class (DGS) in accordance with the user-specified delay requirements and the actual network conditions, and it assigns different priority levels to the session requests within the DGS class by a method of probabilistic analysis based upon a stochastic system model which tends to minimize the difference between the worst-case delay and the average delay.

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Delay-Guaranteed Service for Store-And-Forward Networks

This control procedure guarantees a maximum end-to-end delay per session for data communication traffic within a designated service class in a store-and-forward network having virtual circuits and fixed routing. At each node in the network the procedure limits the number of active sessions which can be accepted into the delay-guaranteed service class (DGS) in accordance with the user-specified delay requirements and the actual network conditions, and it assigns different priority levels to the session requests within the DGS class by a method of probabilistic analysis based upon a stochastic system model which tends to minimize the difference between the worst-case delay and the average delay. As used herein, the term "data communication" should be understood to mean digitized speech transmission as well as the transmission of alphanumeric information. When a user requests a data communication session and specifies a guaranteed maximum delay, the session request is placed in the DGS class only if it can be accommodated there at that time.

The number of sessions within the DGS class is variable but may not exceed a maximum number (MAXNUM) which determines the portion of network capacity that can be used by DGS traffic. The control procedure requires that the amount of traffic imposed per session
(i.e., the number of message packets per time unit) be limited and that a unique maximum packet length be defined throughout the network. Each member of the DGS population is assigned an individual priority, and MAXNUM is the number of different priority levels (it being understood that the term "priority" as used herein means priority within the DGS class). MAXNUM also is the maximum number of sessions that a node can accept within this class. Homogeneous line capacities are not required, although for the purpose of analysis it may be assumed that such capacities are uniform, as will be explained later. Additional terms which will be employed herein are: SRP - Session request packet

MAXD - A field within the SRP which designates the

required maximum end-to-end delay.

ACTD - Another field within the SRP, initially zero,

which is used to accumulate the total maximum delay

guaranteed by the network.

PODT - Priority-oriented delay table, described below. A PODT exists for each outgoing line, and it contains one entry for each priority level specifying the maximum delay for that level and an identification of the session (if any) currently allocated to that level, as shown in Fig. 1. The procedure for establishing a session is as follows: 1. The source node sends a SRP including the specification of the maximum delay (MAXD field) towards the

destination. 2. The source node and all intermediate nodes obtain the

highest free priority level from their PODT, assign the

requested session to it, and add the corresponding MAXD

value to the ACTD field of the SRP. 3. If there is no priority level a...