Enterasys Networks CSX6000, CSX5500, CSX7000 manual Maximum Window Size

USER’S GUIDE

X.25 RELIABILITY, WINDOWS, AND ACKNOWLEDGMENT

X.25 SEQUENCE NUMBER RANGE

The type of sequence numbers to be used for X.25; regular or extended. Extended sequence numbering allows for packets to be assigned sequence numbers from 0-127 (modulo 128), as opposed to 0-7 (modulo 8). The default value is modulo 8.

MAXIMUM WINDOW SIZE

This is the largest possible window size to be supported on any virtual circuit. The window size is the number of frames that a DTE can send without receiving an acknowledgment. SVCs that support window size negotiation will never allow the agreed upon window size to exceed this value. Using modulo 128, the DTEs can send up to 127 frames without receiving an acknowledgment. Using modulo 8, the DTEs can send up to 7 frames without receiving an acknowledgment. The default value for both modulo 8 and modulo 128 is 2.

MAXIMUM PACKET SIZE

This value is used to determine the maximum packet size that the system will support for X.25 connections. When packet size negotiation is performed on SVCs, this value will be used as the upper bound. The default maximum packet size is 128 bytes.

X.25 QUALITY-OF-SERVICE FACILITIES

The X.25 Quality-of-Service Facilities apply only to SVCs. The first three configuration elements are for SVCs that support negotiation.

MAXIMUM THROUGHPUT CLASS

This value is used to determine the maximum throughput class that the system will support for X.25 connections. Throughput describes the maximum amount of data that can be sent through the network, when the network is operating at saturation. Factors influencing throughput are line speeds, window sizes, and the number of active sessions in the network. When throughput class negotiation is performed on SVCs, this value will be used as the upper bound. The default value is 19,200 BPS.

FLOW CONTROL NEGOTIATION

This configuration element specifies whether Flow Control Negotiation is to be supported for SVCs (negotiation is not performed on PVCs). If Flow control negotiation is supported for SVCs, the window and packet sizes can be negotiated between DTEs on a per-call basis. As a default, this facility is not supported.

THROUGHPUT CLASS NEGOTIATION

This configuration element specifies whether Throughput Class Negotiation is to be supported for SVCs (negotiation is not performed on PVCs). This facility allows the throughput rates to be negotiated between DTEs on a per-call basis. As a default, this facility is not supported.

Note: The next 6 items configured for the X.25 Quality of Service Facilities are the non- standard default parameters for SVCs that do not support negotiation. These pa- rameters are used on SVCs that do not use the standard X.25 values, but also do not support any facility negotiation.

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