Server User Manual

76 System description

Fallback in IP Trunk 3.01 (and later)

In QoS monitoring, the local node queries the remote node and gets a

response; the remote node queries the local node and gets a response.

If the remote node cannot query the local node, QoS monitoring is not

available. When an IP Trunk 3.01 (and later) node uses a Gatekeeper to

resolve an address, IP Trunk 3.01 (and later) cannot monitor QoS and

provide fallback. This function resides with the device resolving the address.

As a result, for all calls going to the Gatekeeper, such as in IP Peer

Networking, no fallback can occur. The call either goes through with

possibly a lower QoS, or the call clears instead of falling back. All QoS

control is in the hands of the Gatekeeper.

However, for calls using the ATPM static address tables, the IP Trunk 3.01

(and later) Leader retains awareness of network status and can cause

fallback to the PBX, if needed.

The full QoS fallback function is available for locally provisioned addresses.

IP Peer and Qos

The IP Peer Networking nodes do not support QoS monitoring. The

capability must be enabled for both sides in order for it to work, but it

cannot be enabled for IP Peer Networking. Therefore, do not enable QoS

monitoring for any numbers terminating on an IP Peer Networking node. If

this is done, the IP Peer Networking node is unreachable for that IP Trunk

3.01 (and later) node.

IP Trunk 3.01 (and later) nodes can perform QoS monitoring only on remote

IP Trunk 3.01 (and later) nodes provisioned locally with SL1, SL1 with ESN5

node capabilities.

Return to the IP network

Unless the DCH is down and all trunks appear busy to the system, outgoing

calls are introduced to the IP Trunk 3.01 (and later) node. Each call is tested

against the outgoing address translation and Quality of Service (QoS)

for the destination node. After the QoS returns to an acceptable level,

all new outgoing calls are again routed through the IP network. The call

connections that were established under the fallback to alternate facilities

condition are not affected.

Type of Service

The IP packet handler has a byte of data for Type of Service (ToS). This

byte allows the user to indicate a packet’s priority so that routers can more

efﬁciently handle data packets. For example, a router can decide to queue

low priority data while immediately passing packets marked as high pr iority.

Nortel Communication Server 1000

IP Trunk Fundamentals

NN43001-563 02.01 Standard

Release 5.5 21 December 2007