Page 20 - Overview of Secure VPN Implementation
Bandwidth Calculation Variables
Variable Description
Option
Values
L2_ header
Frame Relay
R FR12
Assuming 2 bytes Frame Relay header.
5
Frame Relay
Multilink PPP
Assuming 2 bytes Frame Relay header
6
Ethernet The
Ethernet
header without the CRC
+ 4 bytes
CRC
14
PPP (WAN)
2
Tunneling _header
L2TP
The L2TP header comprising:
IP = 20, UDP = 8 and L2TP header =11
39
G723 52
G729 52
Net 8K
52
IPSec
The IPSec header comprising the IP and ESP header
(Tunnel Mode). The values specified here also include the
ESP padding value. Use the appropriate IPSec header
value to match the codec.
G711 56
VoIP header
VoIP_header
The VoIP header comprising the IP, UDP and RTP
headers and is dependant on whether link is running IPHC.
With
IPHC
4
Fax header
Fax_header
See note below:
The Fax header comprising:
IP = 20, UDP = 8, RTP = 12 and Avaya info = 6
Without
IPHC
46
Payload
Payload
The number of bytes per sample
Type
Value
VOIP
G711
G723
G729
Net 8K
160
24
20
20
Fax
14400
12000
9600
7200
72
60
48
36
Sample Rate
Payload_per_sec
The number of samples per second
Type
Value
VOIP
G711
G723
G729
Net 8K
50
33.3
50
50
Fax ((bytes to bits conversion is implicit))
14400
12000
9600
7200
200
200
200
200
Bytes to Bits per second
Bit__conversion
Transmission speeds are always specified in Bits Per
Second (BPS). The multiplication factor of 8 (i.e. X 8) is
used to convert the calculation to bytes per second
8
Note:
Fax bandwidth varies throughout the call, and is quite asymmetrical. It first
starts out as RTP, then there is a period of relatively little bandwidth as the
systems handshake, then there is asymmetrical bandwidth as the fax is
transferred and the acknowledgements come back. E.g. there will be transitory
periods during a "fax" call, where it will want the bandwidth of a voice call with
the configured characteristics.
Page 20 - Overview of Secure VPN Implementation
IP Office (R3.0)
Typical VPN Deployment
40DHB0002UKER Issue 3 (4th February 2005)
