TCP/IP Management Programming Manual

Introduction
HP NonStop TCP/IP Management Programming Manual—529636-001
1-4
Relationship With Other Subsystems
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Relationship With Other Subsystems
The TCP/IP subsystem provides a file-system interface to the TCP, UDP, and IP of the
TCP/IP family. TCP or UDP provides services at the Transport Layer (Layer 4 in the
OSI model), and IP provides services at the Network Layer (Layer 3). The TCP/IP
subsystem relies on the SLSA subsystem for the Link and Physical Layers.
The SLSA subsystem provides the Link Layer (Layer 2) and Physical Layer (Layer 1)
for the NonStop TCP/IP subsystem.
Figure 1-1 on page 1-5 shows the relationship between the NonStop TCP/IP and SLSA
subsystems.
Note that Figure 1-1 on page 1-5 also includes the relationship between the TCP/IP
subsystem and the X25AM subsystem. SLSA is used indirectly by SCF or an SPI
application to add the #IP, #ARP, and #SNAP filters. X25AM is used to add the
#TCPIP1 through #TCPIP32 subdevices on an X.25 line. It is through these
subdevices that the TCP/IP subsystem can interface with an X.25 network. For further
details on the relationships between these subsystems, see the TCP/IP Configuration
and Management Manual.
The TCP/IP process interfaces to the Ethernet adapters (E4SAs, FESAs, and G4SAs)
and token ring ServerNet adapters (TRSAs) through the SLSA subsystem and to the
SLSA subsystem driver/interrupt handlers (DIHs) through the ServerNet fabrics of the
system. As shown in Figure 1-1 on page 1-5, the SLSA subsystem provides logical
interfaces (LIFs) through which packets pass to filters. Packets pass through the rest of
the SLSA subsystem, which consists of ServerNet Addressable Adapters (SACs) and
physical interfaces (PIFs), and then out to a LAN, WAN, or X.25 connection. A brief
description of the SLSA components relevant to this discussion follows Figure 1-1 on
page 1-5.
Note. Token ring is not supported in this release.