The MIB module for management of Cisco specific Data Link
Switching protocol enhancements.  DLSw is described in 
RFC 1795 and RFC 2024.
        
DLSw+ Defined
        
Data link switching Plus (DLSw+) is a means of transporting
Systems Network Architecture (SNA) and NetBIOS traffic over
an IP network. The end systems can attach to the network over
Token Ring, Ethernet, Synchronous Data Link Control
(SDLC) protocol, or Qualified Logical Link Control (QLLC).
DLSw+ switches between diverse media, and locally terminates
the data links, keeping acknowledgments, keepalives, and polling
off of the WAN. Local termination of data links also
eliminates data link control time-outs that can occur during
transient network congestion or when rerouting around failed
links. Finally, DLSw+ provides a mechanism for dynamically
searching a network for SNA or NetBIOS resources and
includes caching algorithms that minimize the broadcast traffic
required. 
        
In this document, DLSw+ routers are referred to as
peers, or partners. The connection between two DLSw+
routers is referred to as a peer connection. A DLSw circuit is
comprised of the data link control connection between the
originating end system and the originating router, the connection
between the two routers (typically a TCP connection), and
the data link control connection between the target router and
the target end system. A single peer connection can carry
multiple circuits.
        
The transport connection between DLSw+ routers can vary according
to the needs of the network and is not tied to TCP/IP
as the DLSw standard is. Cisco supports four different transport
protocols between DLSw+ routers:
        
TCP/IP-for transport of SNA and NetBIOS traffic across WANs where
local acknowledgment is required to minimize
unnecessary traffic and prevent data-link control timeouts and
where non-disruptive rerouting around link failures is
critical. This transport option is required when DLSw+ is
operating in DLSw standards mode. 
        
FST/IP-for transport across WANs with an arbitrary topology and
with sufficient bandwidth to accommodate SNA
and NetBIOS traffic. This solution allows for rerouting around
link failures, but recovery may be disruptive depending
on the time required to find an alternate path. This option does
not support local acknowledgment of frames. 
        
Direct-encapsulation for transport across a point-to-point or
Frame Relay connection where the benefits of an
arbitrary topology are not important and where nondisruptive
rerouting around link failures is not required. This option
does not support local acknowledgment of frames. 
        
DLSw Lite-also known as Logical Link Control, Type2 (LLC2)
encapsulation -for transport across a point-to-point
connection (currently only Frame Relay is supported) where
local acknowledgment and reliable transport are
important, but where nondisruptive rerouting around link
failures is not required. DLSw Lite uses RFC 1490
encapsulation of LLC2.