Introduction to Tandem X.25 Capabilities

Flexible Call-Setup
Tandem X.25 Features and Capabilities
2–8 065307 Tandem Computers Incorporated
Negotiation of Window Size
This facility allows the user to negotiate an appropriate window size during call setup.
X25AM accepts any Incoming Call packet that requests window-size negotiation.
However, window-size negotiation is included in a Call Accepted packet only when
the subdevice issuing the response is configured to negotiate window size
(NEGOTIATE attribute).
X25AM includes window-size negotiation in a Call Request packet only if the
subdevice issuing the request is configured for window-size negotiation.
Negotiation of Packet Size
This facility allows the user to negotiate an appropriate packet size during call setup.
The limits on packet sizes depend on the packet sizes supported by the network
provider. Some users subscribe to more than one network. And some networks use
different packet-size options for the DTE to DCE, DTE to PAD, and X.75 gateway
interfaces.
X25AM accepts an Incoming Call packet that requests packet size negotiation if the
requested packet size is less than or equal to the system generation packet-size
modifier (PACKETSIZE). If the incoming call packet size is less than the value of
PACKETSIZE, the call is assigned to a subdevice configured to negotiate packet size.
If the packet size of the incoming call is greater than PACKETSIZE, the call is cleared.
X25AM includes packet-size negotiation in a Call Request packet only if the subdevice
issuing the request is configured for packet-size negotiation(NEGOTIATE attribute).
Negotiation of Throughput Class
This facility allows the user to negotiate an appropriate throughput class during call
setup. If a throughput class is not accepted, the DCE can lower the requested
throughput to the subscribed value.
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.
The throughput-class negotiation facility allows the throughput rates to be negotiated
on a per-call basis. A throughput greater than the DTE’s default value is not allowed.
The allowable rates that can be negotiated are 75, 150, 300, 600, 1200, 2400, 4800, 9600,
19,200, and 48,000 bits per second.
X25AM accepts any Incoming Call packet that requests throughput-size negotiation.
However, throughput-size negotiation is included in a Call Accepted packet only
when the subdevice issuing the response is configured to negotiate throughput size.
X25AM includes throughput-size negotiation in a Call Request packet only if the
subdevice issuing the request is configured for throughput-size negotiation
(NEGOTIATE attribute).