McDewey

Now consider a branch-to-branch connection in a star-topology network where the C7200 in the headquarters site tandems the call to the destination branch. In this case the signal stays in compressed format through the central C7200. This results in considerable savings in the delay budget with respect to the next example, Two-Hop Connection Over A Public Network With A PBX Tandem Switch.
Table 6.2: Two Hop Public Network Delay Calculation with Router/Gateway Tandem
Delay Type
Fixed (ms)
Variable (ms) Coder Delay, χ1
18

Packetization Delay, π1
30

Queuing/Buffering, ß1

8 Serialization Delay (64 kbps), σ1
5

Network Delay (Public Frame), ω1
40 25 Tandem Delay in MC3810, τ1
1

Queuing/Buffering, ß2

0.2 Serialization Delay (2 Mbps), σ2
0.1

Network Delay (Public Frame), ω2
40 25 De-jitter Buffer Delay, Δ1
75

Totals
209.1 58.2 Page 12 of 18 Cisco - Understanding Delay in Packet Voice Networks 7/31/2008 http://kbase.cisco.com/paws/servlet/ViewFile/5125/delay-details.xml?convertPaths=1