NEC Sl2100 Networking Manual page 126

SL2100
• Ethernet = 18 Bytes
• 802.1Q/P Ethernet = up to 32 bytes
• PPP = 9 Bytes
• Frame Relay = 6 Bytes
• Multilink Protocol = 6 Bytes
Bandwidth Calculation
( [ Layer 2 overhead + IP/UDP/RTP header + Voice Payload ] / Voice Payload ) * Default CODEC
speed = Total Bandwidth
Example of a G.711 call over Ethernet using a 20ms packet size and not using RTP header
compression
(.020 * 64000) / 8 = 160 Bytes for Voice Payload
([ 18 + 40 + 160] / 160) * 64000 = 87200bps
If VAD is not enabled each side of the conversation would be streaming 87.2kbps in one direction for a
total of 174.4kbps.
The following chart shows the supported CODECS for IP phones with different packet sizes over PPP
and Ethernet.
CODEC
G.711
G.711
G.711
G.711
G.722
G.722
G.722
G.722
G.729
G.729
G.729
G.729
G.729
G.729
13.8 Some Network Considerations
When adding the SL2100 to a customers network there are many things to be aware of. Before
implementation a detailed network diagram of the existing network must be obtained from the
customer. This diagram may provide you with information about possible network conditions that can
prevent or hinder the VoIP equipment from functioning correctly.
9-28
Packet Size
10
20
30
40
10
20
30
40
10
20
30
40
50
60
PPP
103.2 kbps
83.6 kbps
77.1 kbps
73.9 kbps
103.2 kbps
83.6 kbps
77.1 kbps
73.9 kbps
47.2 kbps
27.6 kbps
21.1 kbps
17.8 kbps
15.9 kbps
14.5 kbps
IP Multiline Station (SIP)
ISSUE 1.0
Ethernet
110.4 kbps
87.2 kbps
79.5 kbps
75.6 kbps
110.4 kbps
87.2 kbps
79.5 kbps
75.6 kbps
54.4 kbps
31.2 kbps
23.5 kbps
19.6 kbps
17.3 kbps
15.7 kbps