Introduction

General Overview

The Connection Layer controls the state of the air-link, and it prioritizes the traffic that is sent over it.

This section presents the default protocols for the Connection Layer. With the exception of the Overhead Messages Protocol, each of these protocols can be independently negotiated at the beginning of the session.

The access terminal and the access network maintain a connection whose state dictates the form in which communications between these entities can take place. The connection can be either closed or open:

• Closed Connection: When a connection is closed, the access terminal is not assigned any dedicated air-link resources. Communications between the access terminal and the access network are conducted over the Access Channel and the Control Channel.

• Open Connection: When a connection is open, the access terminal can be assigned the Forward Traffic Channel, and is assigned a Reverse Power Control Channel and a Reverse Traffic Channel. Communications between the access terminal and the access network are conducted over these assigned channels, as well as over the Control Channel.

The Connection Layer provides the following connection-related functions:

• Manages initial acquisition of the network.

• Manages opening and closing of connections.

• Manages communications when connection is closed and when a connection is open.

• Maintains approximate access terminal's location in either connection states.

• Manages radio link between the access terminal and the access network when connection is open.

• Performs supervision both when the connection is open and when it is closed.

• Prioritizes and encapsulates transmitted data received from the Session Layer and forwards it to the Security Layer.

• De-capsulates data received from the Security Layer and forwards it to the Session Layer.

The Connection Layer performs these functions through the following protocols:

• Air Link Management Protocol: This protocol maintains the overall connection state in the access terminal and the access network. The protocol can be in one of three states, corresponding to whether the access terminal has yet to acquire the network (Initialization State), has acquired the network but the connection is closed (Idle State), or has an open connection with the access network (Connected State). This protocol activates one of the following three protocols as a function of its current state.

• Initialization State Protocol: This protocol performs the actions associated with acquiring an access network.

• Idle State Protocol: This protocol performs the actions associated with an access terminal that has acquired the network, but does not have an open connection. Mainly, these are keeping track of the access terminal's approximate location in support of efficient Paging (using the Route Update Protocol), the procedures leading to the opening of a connection, and support of access terminal power conservation.

• Connected State Protocol: This protocol performs the actions associated with an access terminal that has an open connection. Mainly, these are managing the radio link between the access terminal and the access network (handoffs, handled via the Route Update Protocol), and the procedures leading to the close of the connection.

In addition to the above protocols, which deal with the state of the connection, the Connection Layer also contains the following protocols:

• Route Update Protocol:This protocol performs the actions associated with keeping track of an access terminal's location and maintaining the radio link between the access terminal and the access network. This protocol performs supervision on the pilots.

• Overhead Messages Protocol: This protocol broadcasts essential parameters over the Control Channel. These parameters are shared by protocols in the Connection Layer as well as protocols in other layers. This protocol also performs supervision on the messages necessary to keep the Connection Layer functioning.

• Packet Consolidation Protocol: This protocol consolidates and prioritizes packets for transmission as a function of their assigned priority and the target transmission channel.

The Air Link Management Protocol, its descendants and the Overhead Messages Protocol are control protocols. The Packet Consolidation Protocol operates on transmitted and received data.