Comrex BRIC-Link II, Руководство по эксплуатации продукта

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XVI.
MAKING EBU3326/SIP COMPATIBLE CONNECTIONS
Comrex codecs u lize a set of protocols that allow easy IP connec ons to other Comrex codecs (as many other
brands do for their own hardware). In general, when establishing connec ons between Comrex hardware, it’s best
to use these proprietary modes to take the most advantage of the features of the product.
However, many users have concerns about ge ng “locked in” to a certain codec brand. Because of this, an
interna onal commi ee called N/ACIP was formed by the European Broadcast Union to hammer out a common
protocol to interconnect codec brands. This commi ee resulted in the establishment of
EBU3326 , a technical
document describing how best to achieve this goal.
ABOUT EBU3326
EBU3326 by and large establishes a set of features each codec should support, and then leaves most of the heavy
li ing to other, previously established standards like SIP (IETF RFC 3261). Topics not covered (yet) by EBU3326
include things like carrying ancillary data, contact closures from end-to-end, codec remote control, monitoring, and
complex NAT traversal—which at this point are s ll le to the individual manufacturer’s discre on. If these topics
are important to a user’s applica on, it’s best to s ck to a single codec vendor and their proprietary protocols.
The Tech 3326 document de fi nes several mandatory encoding algorithms, and the transport layer that could be
used on them for compa bility. But the most complex part of the standard was the decision on how to arrange
Session Ini aliza on, which is the handshake that takes place at the start of an IP codec call. The most commonly
used protocol is called
SIP , which is used extensively by VoIP phones and therefore was a logical choice. SIP carries
the advantage of making BRIC-Link II compa ble with a range of other non-broadcast products, like VoIP hardware,
so ware, and even mobile phone apps.
EBU3326 IN BRIC LINK II
BRIC-Link II does not fully comply with EBU3326, as it does not feature the mandatory MPEG Layer II codec. Aside
from this, BRIC-Link II has been tested to be compa ble with several other manufacturer’s devices using encoders
supported by both products. When using
EBU3326/SIP Compa ble mode (selectable in the user interface),
ancillary data, contact closures, Switchboard TS, Mul streaming and Mul cas ng are not supported. Outgoing
call pro
fi les built with the EBU3326/SIP channel may lack some advanced op ons, and can not be set for di ff erent
encoders in each direc on (i.e., EBU3326/SIP calls are always symmetrical).
EBU3326/SIP MODES
A func on of placing a SIP-style call is the ability to register with a SIP server. This is a server that exists somewhere
on the network, usually maintained by a service provider. Several free servers exist that can o
ff er registra on, such
as Onsip.com .
The BRIC-Link II allows EBU3326/SIP calls to be placed or received with or without registra on on a SIP server. If
registra on is not enabled, connec ons are made directly to the compa ble device by dialing its IP address, just like
in
BRIC Normal mode. Connec ons with registra on enabled are fi rst made between the local codec and the SIP
server, and are then routed to the compa ble device once the server responds.