Introduction to Networking for NonStop S-Series Servers

Open Systems Interconnection (OSI) Network
Connections
Introduction to Networking for HP NonStop S-Series Servers—520670-005
8-15
Network and Data Link Interfaces
Network and Data Link Interfaces
WAN and LAN connectivity for HP NonStop OSI is provided by the HP X.25 Access
Method (X25AM) subsystem and the Port Access Method (PAM) subsystem,
respectively. TCP/IP connectivity for HP NonStop OSI is provided by either X25AM or
PAM. OSI/TS can run over either X25AM or PAM; it also implements the Internet
Protocol (IP) for use over the PAM or X25AM subsystem. Additionally, X25AM and
PAM both offer programmatic interfaces, so you can develop applications that directly
use WAN or LAN services.
X.25 Access Method (X25AM)
X25AM enables a NonStop S-series server to connect to a public or private PSDN that
supports ITU–T (formerly CCITT) X.25 Recommendations. These networks include
TELENET and TYMNET in the United States, DATAPAC in Canada, PSS in the United
Kingdom, DATEX-P in Germany, European Telecommunications Standard NET 2, and
many more.
NonStop S-series servers communicate over X.25 networks using the High-Level Data
Link Control (HDLC) bit-synchronous protocol. A NonStop S-series server can support
multiple connections to one or more X.25 networks. X25AM supports communications
with networks that support features defined in either the 1980 or the 1984 CCITT
standard for PSDNs. It can also be used for direct connections without
packet-switching.
A product related to X25AM is X3PAD, which is an application that emulates an X.3
packet assembler/disassembler (PAD). X3PAD enables a terminal connected to a
NonStop S-series server to use X25AM software, which in turn allows the terminal to
communicate with a system other than a NonStop system across an X.25 network. The
terminal can operate only in conversational mode. See Section 6, Device-Specific
Connections, for more information about X3PAD.
Port Access Method (PAM)
The PAM subsystem is an independent interface that allows applications access to
Ethernet and token-ring LANs. PAM provides access to Ethernet LANs through the
ServerNet LAN systems access (SLSA) subsystem and Ethernet 4 ServerNet adapters
(E4SAs), Fast Ethernet ServerNet adapters (FESAs), Gigabit Ethernet ServerNet
adapters (GESAs), and Gigabit Ethernet 4-port ServerNet adapters (G4SAs). It
provides access to token-ring LANs through the SLSA subsystem and Token-Ring
ServerNet adapters (TRSAs).
Using the PAM subsystem, an application can access two different types of port
interfaces: Link Level Control Type 1 (LLC1) and Ethernet. The PAM subsystem views
the OSI/AS and OSI/TS subsystem as PAM clients. PAM clients are subsystems or
use applications that need to use the port interface using file-system calls. The OSI/AS
and OSI/TS subsystems use the LLC1 port interface.