Introduction

This Part of the Cellular Digital Packet Data (CDPD) System Specification defines a protocol for the exchange of routing and registration information between a Mobile End System (M-ES) and a serving Mobile Data Intermediate System (MD-IS). This part was originally known as Part 407.

This protocol is connectionless and is designed to operate in close conjunction with protocols providing connectionless mode network service, such as Connectionless Network Protocol (CLNP) [ISO-8473] and Internet Protocol (IP) [RFC-791]. It is also designed to operate in conjunction with the Mobile Network Location Protocol (Part 501) for providing Mobility Management services in the CDPD Network.

This protocol provides configuration information about M-ESs to MD-ISs. An MD-IS is informed of the Network Entity Identifiers (NEIs) supported by each M-ES and the subnetwork point of attachment (SNPA) address of the M-ES. That is, a serving MD-IS obtains information that allows it to associate destination network addresses to specific channel streams and to specific data link connections on the channel stream. Once the MD-IS obtains this information, reachability information and routing metrics concerning these NEIs may be disseminated to other MD-IS for the purpose of calculating routes to/from each M-ES on the subnetwork.

This protocol performs logically the same functions specified in [ISO-9542]. However, the characteristics of the CDPD environment invalidate the operation of [ISO-9542] as follows:

a. The Redirection subset of [ISO-9542] is invalidated by the Radio Frequency (RF) subnetwork topology, which is a point-to-multipoint star subnetwork type. All data traffic originating from an M-ES is received by, and only by, a single MD-IS controlling the subnetwork channel. There are no better paths to use when forwarding Network Protocol Data Units (NPDUs) to their destination.

b. Portions of the Configuration subset of [ISO-9542] are invalidated by the RF subnetwork topology and presence of a single MD-IS on the subnetwork channel to which the M-ES is attached. Direct M-ES to M-ES communication is not possible, nor can NPDUs be routed other than through the single MD-IS on the subnetwork.

c. It is desirable for an M-ES to be able to deregister specific NEIs from the CDPD Network in a controlled manner.