3Com NBX, Installation Manual

Page: 229 / 248

C
G
UIDELINES FOR
C
ONNECTING
R
EMOTE
A
UDIO
D
EVICES
This appendix provides guidelines for connecting a remote audio device
to an NBX System. The remote audio device can be a 3Com Telephone,
an Analog Line Card, an Analog Terminal Adapter (ATA), an Analog
Terminal Card, a Digital Line Card, or other product.
For instructions on configuring an NBX device to connect over a
broadband connection (for example, a 3Com Telephone in your home,
behind a DSL Router) see
“Adding a Remote Telephone” in Chapter 2 of
the NBX Administrator’s Guide.
The guidelines provided are for a single device, but the issues discussed
can be scaled to cover multiple devices. The guidelines include the
following topics.
■
Maximum Transfer Unit (MTU)
■
Communication Latency Requirements
■
Bandwidth Requirements
■
Installing Fax Machines with ATAs
Maximum Transfer
Unit (MTU)
The system requires that the interconnection mechanism provide an
apparent MTU of a full size IEEE 802.1 packet (1514 bytes of information
plus 4 byte CRC). The interconnection can fragment packets into smaller
frames but
must reassemble the packets prior to delivery to any NBX
device. The NBX devices do not presently support IP (or other) packet
fragmentation and reassembly.