Visara LINCS Features - Manual (Page 24)

14
LINCS Features
707021-001
Downstream Protocols
LINCS uses any of the following protocols to communicate with the DSPU:
• Frame Relay/LLC
• LAN/LLC
• SDLC/DAP
• TCP/IP
• X.25
SDLC/DAP
LINCS’ SDLC/DAP feature expands the SNA gateway capabilities into the SDLC environment,
by allowing the LINCS node to support DSPUs (PU type 2.0) over SDLC links. DSPUs are
polled by the LINCS similar to the way a front end processor running NCP does. SNA traffic
is passed through the LINCS node upstream to a host connection. This host connection can be
through a channel attachment or through a LAN attachment, Token Ring or Ethernet.
Downstream device attachments are made using the standard SCC or HSC card of the LINCS
node. Each card is capable of supporting up to 16 PUs downstream over one or more lines,
running up to 64 Kbps each. Lines may be configured to support full-duplex or half-duplex
operations, point-to-point or multidrop, NRZ or NRZI.
Segmentation
The maximum frame size sent to the host and to the DSPU is configured in the link profiles
associated with each gateway circuit. LINCS will perform SNA segmentation in both directions
as required.
Link Termination
LINCS will send a REQDISCONTACT to the host if the link to the DSPU is lost for any
reason. The host is then responsible for the error recovery required to reactivate the link.
LU TO PU Mapping
Host logical unit (LU) to LAN physical unit (PU) mapping permits LU traffic destined for a
LINCS node to be redirected to LLC connected LAN DSPUs. Using this feature, also known
as a PU Concentration, the SNA host has access to DSPUs without requiring a separate PU at
the host for each LAN device. To the host, the LINCS node appears to be a standard PU2.0
device, while to the DSPU, the LINCS node appears to be a PU passthrough gateway. This is
achieved by redirecting the datastream for some of the LINCS node’s LUs onto the LAN
according to the configured LU-PU map.
This feature has the following benefits:
• By mapping LUs instead of PUs to the LAN clients, the number of PUs required on the host
can be reduced.
• The mapped LUs can be pooled and made available to DSPUs on a first-come, first-served basis.