Overview
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EtherTalk demonstrates that AppleTalk is a network architecture
independent of media type. EtherTalk increases AppleTalk's bandwidth
significantly by using Ethernet, an industry standard medium. It also
provides increased throughput for transmission-intensive applications
while implementing the layered features and functionality of the AppleTalk
architecture.
Installation
------------
The EtherTalk card is easy to install and use. You don't need to worry
about the Ethernet Link Access Protocol address assignments. Each
EtherTalk card has a unique address, assigned at the factory and stored on
the card. The driver automatically looks for and uses this address on an
Ethernet network. (The network address is also printed on a label on the
back of the board.)
Features
--------
EtherTalk Macintosh OS software redirects AppleTalk packets from the
printer port to the EtherTalk card. These packets are then encapsulated in
Ethernet Link Access Protocol and then sent out onto the network.
EtherTalk operates at speeds up to 10MBPS. The card can be configured for
use on 'thick' or 'thin' Ethernet networks. (See the EtherTalk Interface
Card manual for configuration details.)
You can connect a LocalTalk node to the printer port with one or more
EtherTalk cards installed, and switch between the printer port or any one
of the EtherTalk cards. Only one AppleTalk path can be active at any one
time, and the 'network' function in the control panel is used to select
the active network. (See Chapter 2 of the EtherTalk User's Guide.) There
is a limit of 254 active EtherTalk users (including bridges) on any one
Ethernet.
Performance
-----------
EtherTalk improves AppleTalk throughput, depending on the level of
'foreign' Ethernet traffic and total available bandwidth. A practical
expectation is an improvement of 1.3 to 3 times over LocalTalk
connections, with a total capacity of 3 to 5 times that of LocalTalk
networks.
Bridges
-------
An EtherTalk Macintosh II can't act as a bridge between a LocalTalk
network and Ethernet. It's possible to write bridging software, but none
is included with the EtherTalk product.
AppleTalk Protocol Notes
------------------------
EtherTalk under Macintosh OS implements AppleTalk according to Inside
AppleTalk specification with some enhancements to allow operation on
Ethernet networks. This means that Ethernet devices that don't implement
these protocols and enhancements will be unable to 'see' the card on an
Ethernet network. This is applicable only under Macintosh OS using
AppleTalk protocol.
Under Macintosh OS, a special driver (.ENET) is utilized to 'push'
packets onto the network. This driver is similar to the LocalTalk driver.
Packets sent by this driver in AppleTalk mode are restricted to 768 bytes
to allow encapsulation by an Ethernet LAP.
These packets will co-exist with TCP/IP, XNS or other Ethernet protocols
on the same network without problem.