Specifications

Technical Concepts Nur für den internen Gebrauch
A31003-H3580-M103-2-76A9, 01-2009
9-8 HiPath 3000/5000 V8 - HG 1500 V8, Administrator Documentation
hg-09.fm
Bandwidth Requirements in LAN/WAN Environments
ESP Header Length: The length of the ESP header depends on the encryption algorithm
used. When using cipher block chaining, the ESP header contains an initialization vector
(marked "IV" in the table above). The length of the initialization vector is identical to the length
of a encryption block.
Padding: Padding with bytes is necessary because the encryption algorithm is based on block
encryption. The entire encrypted portion of the packet (original IP/UDP/RTP Header, Voice
Payload, ESP Padding Header, ESP Padding) must be an integer value that is a fraction of the
encryption block length.
The number of padding bytes needed for voice packets is calculated using the following formu-
la:
(42 + x + y) [bytes] = N x ( 8 or 16 [bytes) // N is an integer.
Bandwidth calculation for the AES encryption algorithm:
Encryption algorithm Block length Length of initialization vector
AES 16 bytes (128 bits) 16 bytes (128 bits)
DES 8 bytes (64 bits) 8 bytes (64 bits)
3DES 8 bytes (64 bits) 8 bytes (64 bits)
Table 9-10 Block Lengths of the Encryption Algorithms
Codec Packet-
ing
Sample
size
(msec)
Pay-
load
(bytes)
Padding
(bytes)
Ethernet
packet
length
Payload
packet
(overhead
in %)
Ethernet
load incl.
preamble
(Kbps)
G.711 20 20 160 6 294 75% 117.6
G.711 30 30 240 6 372 50% 99.2
G.711 40 40 320 6 454 38% 90.8
G.711 60 60 480 6 614 25% 81.9
G.723.1 1 30 24 14 166 500% 44.3
G.723.1 2 60 48 6 182 250% 24.3
G.729A 1 20 20 2 150 600% 60.0
G.729A 2 40 40 14 182 300% 36.4
G.729A 3 60 60 10 198 200% 26.4
Table 9-11 LAN Bandwidth Requirement with AES Encryption – By Codec