Envoy Configuration and Management Manual

Introduction to Envoy
Envoy Configuration and Management Manual—429861-001
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ServerNet WAN Concentrator
Envoy accesses the SWAN concentrator through Compaq NonStop TCP/IP and the
ServerNet LAN Systems Access (SLSA) subsystems. The SWAN concentrator connects
to the NonStop Himalaya S-series server through dual 10Base-T Ethernet connections,
which provide fault tolerance if an Ethernet link or controller fails.
The SWAN concentrator replaces the 3602 byte-synchronous and the 3603
asynchronous controllers. Envoy communicates with the SWAN concentrator to a data
link control (DLC) task which runs in the SWAN concentrator.
There are two DLC tasks: WANENVBSC and WANENVASC. The WANENVBSC
DLC task uses the WAN byte driver, emulating the 3602 controller for NonStop
Himalaya K-series systems, and the WANENVASC DLC task uses the WAN ASYNC
driver, emulating the 3603 controller for NonStop Himalaya K-series systems. The
WAN driver provides an interface to the WAN ports on the CLIP (communications line
interface processor).
The CLIP is the major programmable device within the SWAN concentrator, providing
link-level protocol and a software interface to the server. The CLIP stores and
implements specific communications protocols. There are three CLIPs on one SWAN
concentrator and each CLIP supports two serial ports. The resulting six lines can support
any combination of the following interfaces:
•
RS-232
•
RS-449
•
V. 35
•
X.21
Each CLIP contains a Motorola MC68EN360 quad integrated communications
controller (QUICC) chip. Each CLIP interfaces to both the A and B Ethernet ports and
has two WAN ports.
The configuration rules enable any I/O protocol to share a CLIP with any other I/O
protocol; all combinations are fully supported.
ServerNet WAN Concentrator
Processes within the WAN subsystem, such as the concentrator manager (ConMgr)
process, provide access to the SWAN concentrator.
The ServerNet WAN (SWAN) concentrator provides access to wide area networks on
NonStop Himalaya S-series servers. The SWAN concentrator as it relates to Envoy is
described in this subsection.
The ServerNet WAN concentrator supports:
•
Six half-duplex or six full-duplex lines for each ServerNet WAN concentrator
•
Bell 201, 208, 209, or 212 modems (or equivalents)
(All of these modems must be strapped to provide external clocking; also the 212-
type modem must be strapped for synchronous operation.)