Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-11
Expand Line-Handler Process Layer Functions
OSI Data Link Layer (Layer 2)
The OSI Data Link Layer defines the rules for transmission on the physical medium.
Direct-connect line-handler processes provide one of the following versions of the
High-Level Data Link Control (HDLC) protocol at the Data Link Layer depending on the
communications device used:
•
HDLC using Asynchronous Balanced Mode (HDLC-ABM)
•
HDLC-ABM using Transparent Byte Synchronous Framing
Satellite-connect line-handler processes provide the HDLC protocol using
Asynchronous Balanced Mode Extended (HDLC-ABME) at the Data Link Layer.
Expand-over-NAM line-handler processes use the Data Link Layer services provided
by an X25AM (Expand-over-X.25) or SNAX/APN (Expand-over-SNA) line-handler
process.
Expand-over-IP line-handler processes use the NETIP protocol at the Data Link
Layer. The NETIP protocol provides Expand-over-IP line-handler processes with a
QIO-based interface to send Layer 2 frames over IP-based networks via TCP/IP.
Expand-over-ATM line-handler processes use the NETATM protocol at the Data Link
Layer. The NETATM protocol provides Expand-over-ATM line-handler processes with a
QIO-based interface to send Layer 2 frames over ATM-based networks.
Expand-over-ServerNet line-handler processes use the Data Link Layer services
provided by the ServerNet monitor process, $ZZSCL.
Expand-over-FOX line-handler processes use the Data Link Layer services provided
by the FOX monitor process, $ZZFOX.
The Data Link Layer, or line function, of the Expand line-handler process corresponds
to the Expand SCF LINE object.
OSI Physical Layer (Layer 1)
The OSI Physical Layer provides the ability to transmit and receive bits between
nodes. It specifies the physical medium used and defines the electrical interfaces to
the network and the bit-level data flow.
The Physical Layer (Layer 1) of the Expand subsystem includes the drivers, interrupt
handlers, and hardware communications devices that control the physical line.
Expand-over-IP connections are provided through the Ethernet 4 ServerNet adapter
(E4SA) or the ATM 3 ServerNet adapter (ATM3SA). Expand-over-ATM connections are
provided through the ATM3SA.
The ServerNet wide area network (SWAN) concentrator provides WAN connections for
direct-connect, satellite-connect, Expand-over-X.25, and Expand-over-SNA
connections. SWAN concentrators are connected to the server through dual E4SAs.
The ServerNet/FX adapter provides Expand-over-FOX connections.