TCP/IP Tutorial and Technical Overview - IBM Redbooks

Initialization
During initialization, the LE layer (workstation) establishes the default VC with
the LE server. It also discovers its own ATM address, which is needed if it is to
later set up direct VCs.
Registration
In this phase, the LE layer (workstation) registers its MAC addresses with the LE
server. Other things, such as filtering requirements (optional), can be provided.
Management and resolution
This is the method used by ATM endstations to set up direct VCs with other
endstations (LE layers). This function includes mechanisms for learning the ATM
address of a target station, mapping the MAC address to an ATM address,
storing the mapping in a table, and managing the table.
For the server, this function provides the means for supporting the use of direct
VCs by endstations. This includes a mechanism for mapping the MAC address of
an end system to its ATM address, storing the information, and providing it to a
requesting endstation.
This structure maintains full LAN function and can support most higher layer LAN
protocols. Reliance on the server for data transfer is minimized by using switched
VCs for the transport of most bulk data.
2.10.4 Classical IP over ATM versus LAN emulation
These two approaches to providing an easier way to migrate to ATM were made
with different goals in mind.
Classical IP over ATM defines an encapsulation and address resolution method.
The definitions are made for IP only and not for use with other protocols. So if
you have applications requiring other protocol stacks (such as IPX or SNA), IP
over ATM will not provide a complete solution. However, if you only have TCP or
UDP-based applications, this might be the better solution, because this
specialized adaptation of the IP protocol to the ATM architecture is likely to
produce fewer inefficiencies than a more global solution. Another advantage of
this implementation is the use of some ATM-specific functions, such as large
MTU sizes.
The major goal of the ATM Forum's approach is to run layer 3 and higher
protocols unchanged over the ATM network. This means that existing protocols,
for example, TCP/IP, IPX, NetBIOS, and SNA, and their applications can use the
benefits of the fast ATM network without any changes. The mapping for all
protocols is already defined. The LAN emulation (LANE) layer provides all the
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