OSI/TS Configuration and Management Manual

Introduction
OSI/TS Configuration and Management Manual—424831-001
1-9
Local Area Networks
Local Area Networks
For communicating over LANs, OSI/TS uses the connectionless services of the Tandem
LAN Access Method (TLAM). For S-series systems, it is the Port Access Method
(PAM). ES-IS routing exchange protocol is also supported to allow the dynamic
exchange of routing information in LANs. This protocol facilitates the mapping of
logical addresses (NSAP addresses) to physical addresses (LAN station addresses or
MAC addresses). Software and hardware requirements for communicating over LANs
vary, depending on the media access control sublayer:
•
Network Layer
•
Internet protocol, ISO 8473
•
ES-IS routing exchange protocol, ISO 9542 1988(E)
•
Data Link Layer
•
Logical link control sublayer: IEEE 802.2 LLC1
•
Media access control sublayer: IEEE 802.3 CSMA/CD
•
Physical Layer
•
50-ohm, coaxial, baseband cable for CSMA/CD
Only transport protocol class 4 is used over LANs.
OSI/TS uses the unacknowledged, connectionless service (LLC, type 1) of the IEEE
802.2 standard, which allows two logical link control entities to exchange data without
establishing a data link connection. Refer to the Multilan/TLAM Programming Manual
(for K-series hardware and pre-G06 releases, or PAM Configuration and Management
Manual for S-series hardware G06 and above releases) for more information.
Figure 1-7
illustrates how OSI/TS uses the ES-IS routing exchange protocol to
dynamically exchange routing information in local area subnetworks (ES-IS enabled).
In contrast, Figure 1-8
illustrates a LAN connection with ES-IS disabled. Static routing
is done by mapping the physical addresses onto TSP processes. LAN connections using
the inactive subset of the OSI internet protocol (IP) would look the same as shown in
Figure 1-8.