1. Multilink PPP and Dynamic Bandwidth Allocation

2. Setting up the 3ComImpact Digital Modem for Multilink PPP

Because Multilink PPP is enabled by default, typically no additional configuration is required. However, in some cases, the Multilink PPP Directory Number, Multilink PPP Endpoint Identifier Class, and Multilink PPP Endpoint Identifier information may be required.

Multilink PPP configuration is facilitated through registers S80, S81, S82, and S83, which are described in Table 1.

Table 1: Multilink PPP S Registers

Register  Description

S80       Multilink PPP:
              0 -- Disable
              1 -- Enable (default)
          
S81       Multilink PPP Directory Number:
              If the destination to which you are dialing a Multilink PPP
              call requires two separate directory numbers, you must
              include the second telephone number of up to 15 digits in
              this S register. If left blank, then the number used to dial
              the first link is used.
          
S82       Multilink PPP Endpoint Identifier Class:
              If required, this information is provided by your Internet service
              provider.
          
              1 -- Locally Assigned Address
              2 -- Internet Protocol (IP) Address
              3 -- IEEE 802.1 Globally Assigned MAC Address
              4 -- PPP Magic-Number Block
              5 -- Public Switched Network Directory Number
          
S83       Multilink PPP Endpoint Identifier (up to 20 characters)
              If required, this information is provided by your Internet service
              provider.

Multilink PPP Directory Number

By default, the 3ComImpact External Digital Modem dials the same number for both Multilink PPP channels. If the destination to which the digital modem is dialing to establish the second Multilink PPP channel requires a different telephone number, then this second telephone number must be stored in register S81. By default, this register is empty. If required, you must enter this number prior to dialing a Multilink PPP call. To enter the telephone number, send the following AT command to the digital modem:

AT S81=[telephone number]

Multilink PPP Endpoint Identifier

Some Multilink PPP implementations require the use of a Multilink PPP option called the Multilink Endpoint Identifier. Check with your Internet service provider or system administrator to determine whether this information is required. This option is configured in registers S82 and S83. Register S82 stores the Multilink Endpoint Identifier Class value. Register S83 stores the actual Multilink Endpoint Identifier. Note that this option is not required in most cases, so these registers typically do not have to be changed. If the Multilink Endpoint Identifier is required, these values will be provided by your system administrator or Internet service provider.

To set the Multilink Endpoint Identifier Class, send the following AT command to the digital modem:

AT S82=[class]

To set the Multilink Endpoint Identifier, send the following AT command to the digital modem:

AT S83=[identifier]

Disabling Multilink PPP

You may not want to leave Multilink PPP enabled because of the cost of using two B channels or to have a B channel available for incoming calls. To change the default setting, send the following command to the digital modem to disable Multilink PPP:

ATS80=0

3. Setting up the 3ComImpact External Digital Modem for DBA
4. Access Solutions with the 3ComImpact External Digital Modem
5. Determining Throughput
6. ISDN Routers and Bridges Versus ISDN Modems
7. Interoperability with Equipment from Other Vendors