Axia Analog Node Manual do Utilizador descarregar pdf (Página 25)

3: Advanced Programming • 17

Version 2.0, February, 2007

Clock Master as described below.

Livewire Clock Master

Livewire’s clocking system (see Introduction to

Livewire for details) is automatic and largely transparent

to end users. By default the Axia hardware node with the

lowest Ethernet MAC address will be the clock “master”.

The system will automatically and transparently switch

to a new unit as clock master if need be. We do however

permit you to force clock mastership to a particular node

(not recommended) or set certain nodes as preferred for

clock mastership while maintaining automatic opera-

tion. For example you may prefer to have nodes that are

on backup power be preferred clock masters. Note that

in the automatic modes clock mastership is determined

only when the current master becomes unavailable (add-

ing a new node will not change clock mastership regard-

less of the new node’s setting). The only exception is

the 7 (Always Master) setting. You have the following

choices for this setting:

0 (always slave) – This unit will never be used as

clock master.

3 (default) – The usual setting.

4 (Secondary Master) – Nodes with this setting will

be used as clock masters before those set to 3.

5 (Primary Master) – Nodes set to this setting will be

used as clock masters before those set to 4.

7 (Always Master) – This forces a particular

node to be clock master, even if another node

is currently clock master. If this mode becomes

available then the usual prioritization is used.

IMPORTANT! Only a single node on a Livewire

network should ever be set to 7 (Always Mas

ter). For this reason we do not recommend us

ing that selection.

Livewire Clock Mode

Provided for compatibility with older revisions:

IP low rate (default) – recommended setting

Ethernet – compatible with 1.x ﬁrmware

IP High rate – compatible with 2.1.x master

Receive Buﬀer Size

•

Determines the amount of buffering in the receiver.

Buffering is needed to compensate for jitter in network

packet delivery. Usually the biggest source of the jitter is

the source PC. Real-time performance varies a lot from

one system to another; some computers can provide very

low timing irregularities and allow the receive buffer to

be reduced to achieve lower audio delay. Default setting

is 100 ms.

801.1p tagging, 802.1p VLAN ID, 802.1q

Priority, & DSCP Class of Service

802.1p tagging is necessary within the Livewire net-

work to mark high-priority audio packets . This infor

mation is used by the Ethernet switches in the packet

scheduling and queuing mechanism. It provides low-jit-

ter packet forwarding of Livewire clock and low-latency

audio streams.

On the other hand, Standard streams don’t need tag

ging, because they are not low-latency. By default, stan

dard streams are marked with Type of Service (DSCP

code points) information in the IP header which can be

used by L3 switches to provide better service to our au-

dio streams than to best effort IP trafﬁc.

There is an option to enable L2 802.1p tagging on

standard streams, and this may be used with switches

which do not use the DSCP information included in the

TOS ﬁeld of the IP header. We do not enable this tagging

by default, because it wouldn’t work in cross-over Ether-

net connection to PCs; most network cards do not accept

802.1p frames by default.

You should not need to change these default settings

unless you are building a system which is not based on

our recommendations.

The “VLAN ID” setting is related to the VLAN ID in

Ethernet switches. For instance, in HP switches, VLAN

starts at “0”, but in the web page, “0” is the default. So,

how do you dertermine the correct value?

VLAN ID=0 means that VLAN information is not

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 34 35

Comentários a estes Manuais

Sem comentários

Axia Analog Node Manual do Utilizador Página 25

Comentários a estes Manuais