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Network Bandwidth Management (NBWM)
The SRG interoperates with the Network Bandwidth Management (NBWM) feature in a manner
similar to Media Gateway (MG) 1000B, though only G.711 and G.729 codecs are supported. At
the SRG, a Virtual Private Network ID (VPNI) and Zone ID are entered with values defined by the
main office configuration (see
ACR
on page 40). The VPNI and Zone ID allow the CS 1000 to recognize that H.323 and SIP calls
to and from the SRG are from a specific Bandwidth Management zone.
NBWM allows bandwidth zones to be configured on a network basis so that codec selection and
bandwidth allocation software can identify whether IP telephones or gateways are physically
collocated (in the same bandwidth zone) even though they are controlled by different call servers.
NBWM is used to define the codec selection policy and track bandwidth used for calls that
traverse the WAN (interzone calls) and the LAN (intrazone calls). The bulk of configuration for
NBWM is done at the main office.
Adaptive Network Bandwidth Management (ADBWM)
As with NBWM, only the VPNI and Zone ID are required at the SRG in order to implement he
Adaptive Network Bandwidth Management (ADBWM) feature on the SRG (see
management configuration: NBWM, ADBWM, and ACR
ADBWM uses real-time interaction to enhance the performance of Voice over Internet Protocol
(VoIP) networks. ADBWM adjusts bandwidth limits and takes corrective action in response to
Quality of Service (QoS) feedback. This adjustment occurs dynamically, while calls are in
progress. A call server with ADBWM uses VPNIs and Zone IDs to keep track of the bandwidth
being used between its own zone and zones belonging to other call servers. If the interzone QoS
degrades below an acceptable level, the available bandwidth is reduced automatically between the
two zones. When the QoS between the two zones improves, the bandwidth limit is allowed to
return to normal.
Alternative Call Routing (ACR)
Configuration for Alternative Call Routing (ACR) at the SRG includes datafilling the Virtual
Private Network ID (VPNI) and Zone ID required by NBWM and ADBWM. However, additional
configuration is required and depends on the type of trunking provisioned at the main office:
Attendant service or DID trunks (see
and ACR
on page 40).
ACR for NBWM allows a station-to-station call (that is, a call that does not use a trunk) to
overflow to traditional routes. Overflow can occur if there is insufficient interzone bandwidth
available to carry the call, or if the QoS has degraded to unacceptable levels. The feature applies to
station-to-station calls between a branch office and main office as well as from one branch office
to another branch office, provided both stations are registered to the same main office.
Network administrators who do not want calls to be blocked, yet have a limited amount of
bandwidth available, can use ACR to overflow calls to conventional trunks (PSTN or Tie/MCDN).
ACR allows calls to be routed by overflowing them, trading off the capital cost of WAN
bandwidth against the incremental cost of overflowed calls.
Bandwidth management configuration: NBWM, ADBWM, and
Bandwidth management configuration: NBWM, ADBWM,
Chapter 4 CS 1000 considerations
on page 40).
SRG50 Configuration Guide
39
Bandwidth
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Troubleshooting
