9-2 Smart Switch 1800 4. 0 User Guide , Rev 0 1
Each SNA port can be configured to support SNA hosts (PU 2.1, 4.0 HPAD; NPAD)
or terminals (PU 1.0, 2.0, 2.1 TPAD). A port can also be configured for a transparent
mode (XPAD) , whi ch sup ports HDLC and an y of its su bset protoc ols, such as SD LC
(IBM), LAPB (ISO), and BSC (bisync).
LLC2 (Logical Link Control type 2 ) support in the SmartSwitch 1800 pro vides a local
or remote connection over frame relay (via RFC1490) or X.25 (via QLLC) between
two SNA devices, one attach ed to a LAN an d the othe r attach ed to either an other L AN
or a frame relay-co mpli ant SNA/APP N d evic e. Eac h SNA host and ter mina l acces sing
the SmartSwitch—via SDLC, LLC2, frame relay, or X.25—will appear to a local
LLC2-attached terminal or host as if it is directly connected to the local LAN.
LLC2 support in the SmartSwitch 1800 includes the following scenarios, some of
which are diagrammed in Fi gu re 9-1 (on page 9-3):
●Connection between a LAN-attached host/workstation and SNA devices, via
SDLC-to-LLC2 and LLC2-to-SDLC conversion, over a frame relay or X.25
netw or k (exa m ple 1), or fram e relay PVC (exam ple 4 ).
●Connection between LAN-attached workstations, over a frame relay or X.25
netw or k (exa m ple 2), or a fram e rela y P VC (exa mple 3) .
●Connection between workstations attached to different LANs on the same
SmartSwitch.
Support of end-to-end LLC2 connections requires that the full LLC2 pro-
tocol (not LLC2-R) be configured and loaded in the RLP file, as described
in Chapte r 5 . (LLC2- R does s up port convers i on.)
Protocol conversion is accomplished by terminating an SDLC connection in the
SmartS w itch an d esta bl i shin g an LLC2 c onnec t ion to the SNA host.
The following figure shows some examples of SDLC and LLC2 config urati ons. Note
that the LANs shown are all Token Ring. The same examples can be presented with
Ethe r net LA Ns .