Criteria for Naming Multilink PPP Bundles

Criteria for Naming Multilink PPP Bundles

Multilink PPP allows devices to send data over multiple point-to-point data links to the same destination by implementing a named virtual link. The MP connection has a maximum bandwidth equal to the sum of the component links bandwidth. MP can be configured for all interfaces that support PPP. Refer to RFC 1990 for more information on MP.
Cisco IOS software builds a multilink bundle name based on the PPP authenticated name first, then based on the endpoint discriminator. With Cisco IOS in its default state, all client links that use the same username are bundled together into the same MP virtual connection. For a client using MP, each connection is authenticated by the access server using the same username and added to the same MP bundle. This setup works well when every client uses a unique username to connect to the access server. However, if multiple clients use the same username with MP, some of them are incorrectly added to a bundle initiated by a different client. Another problem occurs when interoperating with non-Cisco routers in a bi-directional dial environment. If the non-Cisco router does not use the authenticated name as a name for the bundle, but the Cisco router does, two different bundles are created.
In situations in which many clients use the same username to initiate an MP connection, or when interoperating with non-Cisco routers, you need to control the order in which the bundle name is created. It is necessary to configure the access server to create a bundle name based on the endpoint discriminator first, the username second, or both. The endpoint discriminator identifies the system transmitting the packet and advises the network access server (NAS) that the peer on this link could be the same as the peer on another existing link. Because every client has a unique endpoint discriminator, only multiple links from the same client are bundled into a single unique MP connection. For example, consider when two PC clients initiate a multilink connection to an access server using the same username. If the multilink bundle name is established based on the endpoint discriminator first, then on the username or on both, the NAS can accurately bundle the links from each client using the endpoint discriminator as a bundle name. This bundle name is unique to the peer system transmitting the packet.
Note: When the authentication on a link is done in one direction only, without the authentication of the peer but with the requirement that the local host authenticate itself with use of the Challenge Handshake Authentication Protocol (CHAP), the username supplied by the peer in its CHAP challenge is treated as the peer authenticated name in order to determine the bundle name.

Ref: Criteria for Naming Multilink PPP Bundles