Specifications

12 IBM Voice Over Frame Relay Perform Guide
2.5 Determining the Correct Frame Relay Parameters
Table 4 shows how to determine frame relay parameters, including CIR, Bc, etc.
Table 4. 2212 Frame Relay Parameters
It is possible to calculate the required voice traffic using Table 5.
Table 5. Efficiency of Packing Using Frame Relay Protocol, 67 Packet Per Second
These rates do not include any voice activity detection (VAD) saving.
Figure 8 shows how to define Bc, CIR, and Minimum IR as a percentage of CIR,
etc.
Parameter Default
Value
Design Hint Example
Line Speed NA NA
CIR NA Voice traffic
(Vocoder rate * number of
channels)
+ Mission-critical traffic
13.3 kbps (Nuera E-celp 9.6 kbps and
Frame packing 1) * 4 ch + 20 kbps
(DLSw) = 64 kbps
CIR Monitor Disable NA
Congestion monitor Enable NA
IR adjustment % increment 12% NA
IR adjustment % decrement 25% NA
Minimum IR as % of CIR 25% 50%-100% to prevent MIR to
go under required Voice
traffic
50
Committed Burst size (Bc) 64 kbps CIR * Tc Tc = 45 and CIR=64kbps,
Bc= 64000 * 0.045= 2880
Excess Burst size (Be) 0 NA
Fragment size 256 bytes Nuera’s recommendations
areinTable6
Vocoder Rate Frame Relay Bandwidth Usage with Voice Frame Packing
1 Packet 2 Packet 3 Packet 4 Packet 5 Packet
4800 bps 8533 bps 6666 bps 6044 bps 5733 bps 5547bps
7470 bps 11203 bps 9336 bps 8714 bps 8403 bps 8217 bps
9600 13333 bps 11466 bps 10844 bps 10533 bps 10347 bps
16000 bps 19733 bps 17866 bps 17244 bps 16933 bps 16747 bps