IBM SC30-3681-08 Valid Values 1 to Default Value, Default external Default-window-size value

Con®guring the X.25 Network Interface

Valid Values: 1 to 239

Default Value: 4

clocking external or internal

To connect to a modem or DSU, con®gure clocking as external. To connect directly to another DTE device, use a DCE cable, set the clocking to internal, and con®gure the line speed.

Default: external

default-window-size value

Sets the window size for the packet level assigned by the router if there is no window-size facility in the Call-Request packet. The range is determined by the National Personality packet modulus (PACKET-EXT-SEQ-MODE).

Default: 2

Example: set default-window-size 3

encoding NRZ or NRZI

Sets the HDLC transmission encoding scheme for the interface. Encoding may be set for NRZ (non-return to zero) or NRZI (non-return to zero inverted). NRZ is the more widely used encoding scheme while NRZI is used in some IBM con®gurations.

Default: NRZ

equipment-type DCE or DTE

Speci®es whether the frame and packet levels act as DCE or DTE. This command has no relation to the cable type in use.

Default: DTE (must be DTE for X.31)

htf addr x.25-node-addr

Sets the local DTE address when DDN is used. It converts the IP address to an X.121 address as opposed to the set address command, which is used to set the local DTE address when CCITT is used.

inter-frame-delay value

This parameter de®nes the minimum delay between transmitted frames. Setting this parameter is useful when interfacing directly to older equipment. This parameter is the amount of time between frames in seconds.

Default: 0

mtu value

Sets the Maximum Transmit Unit (MTU) in bytes. This is the maximum message size that will be delivered to the X.25 interface to package and transmit over the serial line. The range is 576 to 16384.

Default: 1500

If you are encountering packet reassembly timeouts when transferring data over the X.25 interface, you should determine what the minimum packet size is for all LAN or serial interfaces that lead to the end-point, then calculate a more suitable X.25 MTU. You should not directly consider the actual X.25 packet size in this calculation because X.25 tends to use a smaller packet size. X.25 usually sends up to 7 packets at one time before waiting for an acknowledgment.

For example, consider a network topology that includes:

± A Token-Ring LAN having a packet size of 4000

Chapter 27. Con®guring and Monitoring the X.25 Network Interface 329