Description Page 53 of 378
ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation
Quality of Service
Quality of Service (QoS) is the gauge of quality of the IP network between
two nodes. As QoS degrades, existing calls suff er p oor voice and fa x quali ty.
New calls will not be initiated if transmissions degrade below an accepta ble
level.
Behavioral characteristics of the IP network depend on:
• Round Trip Time (RTT)
•latency
• queuing delay in the intermediate nodes
• packet loss
• available bandwidth.
The Type of Service (TOS) bits in the IP packet header can affect how
efficiently data is routed through the network. For further information on
ToS, see “Type of Service” on page59.
Packet jitter related to latency affects the quality of real-time IP
transmissions. For good voice quality, the ITG ISL Trunk card reass embles
the voice packets in an ordered continuous spee ch st ream and pl ays th em out
at regular intervals despite varying packet arrival times.
The user configures a required QoS for the ITG node in MAT. T he QoS value
determines when calls Fal lback to alterna te fa cilitie s due t o poor perform ance
of the data network. The QoS value is between 0.0 and 5.0, where 0.0 means
never Fallback to alternate facilities, and 5 means Fallback to alternate
facilities unless the voice quality is perfect. When the QoS for outgoin g calls,
as measured by the Leader car d , falls below the configured v alue, calls
Fallback to alternate facilities. Once the QoS r ises above the configured
value, all new outgoing calls are routed through the IP network.
Note: QoS is measured per remote gateway. For example, if a given
Leader has three remote leaders in its dialing pl an table, it wi ll perform
three QoS measurements and calculations (one per remote gateway).