PAM Programming Manual

PAM Programming Manual—142482
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Link-Level Interfaces
This section describes link-level programmatic interfaces that provide level-2 services
through link-level service access points (LSAPs). These LSAPs are part of the Port
Access Method (PAM) process. The Level-2 Services for Ethernet (L2S) and token ring
(L2TR) programmatic interfaces allow application programs running on a Himalaya S-
series servers to use the PAM process as a link-level, protocol-compatible, L2S provider
for LANs attached to adapters in Himalaya S-series servers, such as the Ethernet 4
ServerNet adapters (E4SAs) and Token Ring ServerNet adapters (TRSAs). These
interfaces isolate application programs running on the host from the LAN adapters and
the physical medium.
Link-level programmatic interfaces are represented in Distributed Systems Management
(DSM) as PORT objects. LLC1 ports provide IEEE 802.2 Logical Link Control, Type 1
(LLC1) access. Ethernet port types provide a DIX-compatible interface. Ports are
differentiated by DSM object subtype. For information on LLC, refer to the IEEE 802.2,
802.3, 802.4, and 802.5 standards.
Lines and Ports
PAM defines a number of DSM objects for use in configuring and managing the
subsystem. Among these objects are lines and ports, which have a hierarchical
relationship with one another as illustrated in Figure 1-3 on page 1-6.
Each LINE object defines a PAM process running on a Himalaya S-series system. Each
LINE object corresponds to one logical interface (LIF) between the server and an
attached LAN. (LIFs are defined through the SLSA subsystem. For more information
about the SLSA subsystem refer to the LAN Configuration and Management Manual.)
Each line name ($PAM1, for example) corresponds to a logical interface (LIF) to the
applicable adapter, as established at the time of PAM start-up through the Persistence
Monitor or TACL.
Each DSM-related PORT object defines an LSAP to a level-2 service available in PAM.
The service being accessed through a port is determined by the type specified when the
port is added.
L2S and L2TR Formatting Library
The Formatting Library is a set of formatting routines that enable you to code an
application without being concerned with the details of the header formats used by the
programmatic interfaces. The L2S and L2TR Formatting Library contains formatting
routines. Your application should use the appropriate set of routines, passing pertinent
information as parameters to the library routines, which handle the details of buffer
organization, headers, and so on.
The L2S Formatting Library contains an object-code file (OL2SFrmt) for the primitive
formatting functions and a header file for each of the supported languages (TL2SFrmt
for TAL, CL2SFrmt for C, and PL2SFrmt for Pascal). The language-specific file is
divided into two sections, one for data definitions and one for external function
declarations. The files are supplied as part of PAM.