Hypertec ISDN 10T Router manual Data Compression, Calling Line Identification Clid, Callback

Concepts and Principles of Operation

diagram, traffic decreases temporarily before increasing again. Because bandwidth requirements can change suddenly like this, the second B-channel waits for a period of time before closing down. In the above diagram, this value has been set to 5 seconds. You can set this time to suit your own requirements.

At point 4, data drops below the lower traffic load percentage value. Because traffic volume must remain below this threshold for a certain length of time, the second B-channel does not close until point 5 (5 seconds later) has been reached.

Data Compression

Data compression allows the router to send and receive data more efficiently by compressing the data at sending and de-compress the data at receiving. When compression is enabled, the Hypertec Router negotiates using a STAC LZS compression scheme using the Compression Control Protocol (CCP). Hypertec ISDN 10T Router supports both Ascend’s pre-standard compression scheme, and the standard compression scheme as specified by ITEF. Depending on the actual data pattern, the STAC compression algorithm may accomplish the compression ratio of 4:1 against an ASCII file. No data compression can be gained against a file which has already been compressed. When working with the Multilink PPP protocol, the compression algorithm is inappropriate as the frequent packet out-of-sequence condition can cause either end to request a compression history reset.

Calling Line Identification (CLID)

Calling Line Identification (CLI) or Caller ID is a mechanism for identifying incoming calls. You may be able to order CLI from your telephone company as part of your ISDN Service. The Hypertec Router allows one CLID for each Profile. In many circumstances, the incoming call indication signal does not include the Calling Line Identification (directory number) of the device which has just called you, or the Calling Line Identification (CLID) may not be passed to the Hypertec Router . You may want to disable CLID authentication, instead, use the Challenge-Handshake Authentication Protocol (CHAP) for additional security if these circumstances apply.

Callback

Callback is available on ISDN circuits. It allows a router to request a return call from a remote router, meaning that when an incoming call is received on a circuit, the router drops that call and calls back the originating router. This feature allows you to take advantage of any differences in call charges and obtain centralized billing. Callback also provides additional security.

There are two scenarios of Callback operation:

1.Caller ID (CLID)

A call arrives at the Hypertec Router, which has been configured to accept Callback requests with the CLID enabled. The HypertecRouter checks if the CLID matches its CLID configuration. If a match is found, the Hypertec Router rejects the incoming SETUP message and calls back the originator using the number presented by Caller ID. This method means that there is either no charge or a minimal call setup charge (service provider dependent) to the originator. If the originator is not configured to request Callback but the receiving circuit is configured to call back the originator, then when a call arrives it will still be called back. If the originator is configured to request Callback but the receiving end is not configured to call back, the receiving end will accept the call and the originator will pay the cost of the call.

2.PPP

If CLID is disabled in configuration in the Hypertec Router, a call is accepted by the Listener circuit then Callback is negotiated using PPP authentication. This method will mean a small cost is incurred at the originating end since the call has to be accepted before Callback is negotiated. If the PPP negotiation fails then the call is dropped as usual.

Packet Filtering, IP Access List

To provide an additional level of security once the connection is established, the Hypertec Router allows users to configure access lists against the IP traffic. The access list specifies what kind of data

15