Configuring the X.25 Network Interface

7-10 Chapter 7

Reverse Charging Calls - Offers the equivalent of a collect call. It is allowed on a per-call basis and is specified in the Call Request packet by the calling DTE.

Closed User Group (CUG ) - Allows the configuration of one or more virtual private networks within a larger public network. A user may gather a number of DTEs into a single logical group and restrict the group’s access ability to receive incoming calls or to make outgoing calls to the restricted “open” portion of the network. The number of CUGs is network-dependent. A single DTE can belong to one or more CUGs.

Within the CUG category, you can specify whether a user connection has incoming access (CUG with Incoming Access), outgoing access (CUG with Outgoing Access), or both. If a DTE belongs to more than one CUG, you must also specify a preferred (or primary) CUG.

Bilateral Closed User Group (BCUG) - Offers a finer degree of access control than CUGs. Bilateral signifies a CUG relationship that has been limited to a pair of DTEs. Access between the pair of DTEs is unrestricted; however, access to or from any other DTE is not possible.

Maximum Packet Size - Specifies the largest packet size that can be negotiated on a per virtual circuit basis.

Window Size - Specifies the largest value, per virtual circuit, to be negotiated in a Window Size facility parameter field. The maximum value for this parameter is dependent upon which Packet Sequencing Modulo method you selected.

D-Bit Procedure Authorization - Not configurable

A DTE subscription with a PDN can include a provision to allow or disallow a remotely originated, reverse-charged call from reaching that DTE (Reverse Charging Acceptance). Charged calls, that is, locally generated call requests, must specify reverse charging.

Emulex X.25 additionally provides local configurable options for both of the preceding items. Regardless of a customer's PDN subscription, all inbound reverse-charged calls can be rejected and all outbound call attempts that do not specify reverse charging can be disallowed.