The MIB module for Airline Protocol Support.

**************************************************************
*                    Acronym Definitions                     *
*                                                            *
* ALPS       : AirLine Protocol Support                      *
* AX.25      : Airline X.25                                  *
* EMTOX      : Exchange of Mixed Traffic over X.25           *
* ASCU       : Agent Set Control Unit                        *
*                                                            *
**************************************************************        


Overview of ALPS (AirLine Protocol Support) MIB
==============================================

MIB description

Document to refer: 'Configuring ALPS' section in Cisco IOS Command
             Reference & Configuration Guide.

The ALPS MIB provides configuration and operational information
for Cisco's Airline protocol support for IBM-P1024B(ALC) and  
Unisys-P1024C(UTS) protocols encapsulation over TCP/IP. The 
following entities are managed:

1. Peers
2. ALPS Circuits
3. ASCUs (Agent Set Control Units)
4. ALC interface
5. ALPS Host link interface to the host

HOST(Emtox/Ax.25) <----> Central <---> IP Network <---> Remote <----> ASCU
                       router                         router

The router connected to the Host is called the Central router and the router 
connected to the ASCU is called the Remote router. We anticipate one Central 
router connecting to a large number of Remote routers. Each router has a 
local peer, which connects to its counterpart on the other router (referred 
to as the remote peer) via a TCP connection. ALPS circuits are set up over 
this TCP connection either on a permanent or on-demand basis. 

A logical grouping of ASCUs are connected via a single circuit - this has 
no connection to the physical interfaces that the ASCUs are connected to. 
The only restriction is that all the ASCUs should be directly connected to 
the same router.

Multiple ASCUs can connect to a single serial interface and several terminals
connect to an ASCU. However, terminals are not visible to the ALPS feature
- the router talks only to the ASCUs. An ASCU can be identified by 
* the interface it is on and its Interface Address (IA) or 
* the circuit it is on, and its A1 and A2 values, which identify it 
             within the circuit. 
Thus there are two ways of identifying an ASCU -  or 
Circuit names are globally unique.

The connection to the host is via one of two flavors of X.25 - either 
AX.25 (for PVCs) or EMTOX (for SVCs). Each X.25 VC corresponds to one ALPS
circuit. There are several hostlinks between a host and the Central router
and load balancing is done across these. EMTOX allows the host to
dial out to a terminal. This requires the use of an X.121 to IP address
translation table to connect to the appropriate remote peer.