TVOICE – Multisite Bandwidth – Strategies for Addressing Bandwidth Concerns

Intro: Anytime you talk about Multisite deployments, bandwidth management must enter the discussion. This Nugget discusses “big picture” bandwidth strategies and walks through QoS and CAC definitions, Region (CODEC) configuration, local conference bridge (CFB), Music on Hold (MOH), and Transcoder (XCODE) configuration, along with the configuration of DSPFarm resources on a router. Now THAT’S a LOT of stuff…


LFI/Serialisation Delay Recap… Delay of packets getting onto the wire.

cRTP – Header compression only not payload


  • CUCM manages codecs using Regions
  • Region uses a prioritised list of codecs
  • Codec mismatch invokes transcoder (If availiable)
  • Not all codecs sound good for all communication types

Using Local Resources

Local Conference Resources

  • Cost: DSP vs BW
  • Actual usage

Local MOH Resources

  • No WAN Music
  • Up to 6 Local MOH sources
  • Multicast-based, phones unaware

Transcoder Usage

  • Transcode: Convert between codes (Slow WAN Link requires smaller sized CODEC, but use a higher quality within a site, hence XCODE requirement)
  • Avoid if possible!
  • DSP Intensive
  • Requires DSPFarm configuration

DSPFarm Configuration Example

‘show diag’ – shows what DSPs are in router

voice-card 1
dsp services dspfarm
Now go and tell UCM about these resources!  (Using SCCP)

sccp local Fa0/0 (Int used to register to UCM)
sccp ccm identifer 1

Now setup DSPFarm..

dspfarm profile 1 transcode
codec g711ulaw
codec g729br8
maximum sessions 1-18 MAX (Be careful)
associate application sccp
no shutdown

Tell router what CCM to register these resources with

sccp ccm group 1
associate ccm 1 priority 1
associate profile 1 register HQ_XCODE (NAME)

DSPFarm is now active and ready for use.

Add Transcoder to UCM! (Easy)