IBM ATM OC-3c - Manual (Page 14)

2-2 C HAPTER 2: N ETWORK L AYER C ONCEPTS
Upper Layer Protocols
The Upper Layer is the layer in the network architecture
that relates to user applications and service requests.
For example, an application could be file transfer
software, and the service request could be a request to
transfer a file from a user’s PC to a shared file server.
User data and control information is passed down the
network layers in the source device, and passed up
the layers at the destination device.
What is LAN Emulation (LANE)?
LAN Emulation (LANE) allows users on Ethernet,
Token Ring, and other traditional LAN networks, to
communicate with each other over an ATM network.
LANE emulates the broadcast nature of traditional
LANs. Each LANE broadcast domain is known as an
Emulated LAN (ELAN).
Each ELAN can only carry one type of traffic. For
example, an ELAN could carry either Ethernet frames
or Token Ring frames, but not both.
There can be several ELANs on a single ATM network.
Some of these ELANs could be carrying Ethernet
traffic and others could be carrying Token Ring traffic.
Traffic from one ELAN is not seen on another ELAN, as
they are logically separate broadcast domains. If devices
from different ELANs need to communicate with each
other, they must do so using an ATM router.
LAN emulation software is contained within ATM
devices which can be added to your existing network.
LANE allows you to add ATM to your network
without having to replace or upgrade the whole of
your underlying technology. LANE allows you to do
this because it is completely transparent to the ATM
network and to the traditional LAN network,
end-users, operating systems and applications.
LAN Emulation allows users on traditional LANs to
communicate over ATM by performing the following
tasks:
■ Emulates the broadcast nature of LANs.
■ Maps MAC addresses to ATM addresses.
■ Maps upper layer connection-less technologies to
the connection-oriented ATM network.
Although LAN Emulation emulates a range of
network technologies, all examples in this guide are
be based on an Ethernet network.