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The direction of the corresponding connection (inbound or outbound) doesn't matter.
Leave empty if you don't need inbound bandwidth management.
Inbound bandwidth management is a contradiction in terms. Priority driven re-ordering
of data packets waiting to be transmitted ususally has to be done on the sending
side of the (Internet) link. Only there it can be done in a reliable way. After all the
packet has already been transmitted on the receiver side. However Internet connectivity
with provider guaranteed Quality of Service / bandwidth management is often very
expensive, so inbound bandwidth managment is an option despite of its limitations.
Inbound bandwidth management reduces the available
bandwidth by up to 20%. It requires that an adequate amount of
the inbound data volume is covered by TCP connections.
Quality of Service (QoS) for Voice over IP (VoIP)
For VoIP the latency time, i.e. the time it takes for a voice packet to travel from sender
to recipient, is very important. Hence SX-GATE's traffic shaper optimizes delivery of
VoIP data packets with a special quality-of-service module.
In order to be recognized as VoIP packet, a data packet
needs to be tagged according to Diffserv-Code-Point Expedited-
Forwarding (DSCP EF).
The amount of bandwidth a single call requires depends on the codec that is used. The
codec defines the compression of a VoIP call. The more compression is applied the
less bandwidth is consumed, however also the quality decreases. The following table
shows the net bandwidth required by commonly used codecs. Some codecs are used
at different bandwidths. In this case the maximum bandwidth is given.
Codec
max. bandwidth (bit/s)
G.711
64000
G.722
64000
G.722.1
32000
G.723.1
6400
G.726
40000
G.728
16000
G.729
8000
