Specifications

Technical Concepts Nur für den internen Gebrauch
A31003-H3580-M103-2-76A9, 01-2009
9-20 HiPath 3000/5000 V8 - HG 1500 V8, Administrator Documentation
hg-09.fm
Static and Adaptive Jitter Buffer
9.4.10 Fax/Modem Channels
Faxes can be sent over transparent G.711 gateway channels and with HiPath 3000/5000 from
V7 R4 or later over T.38 channels (only fax).
T.38 offers the more secure fax transfer method but can only be used at a maximum rate of
14 kbps. Due to the higher processing capacity required for T.38, the number of T.38 channels
is limited. Alternatively G.711 gateway channels can be used for fax transmissions (not for DSL
telephony).
Because of technical restrictions for Internet telephony, modem transfers are not possible.
Note: The number of available G.711 gateway channels is reduced as soon as the DMC inter-
working feature is enabled in HiPath 3000/5000 Manager E.
Fax transmissions over the Internet with G.711 are frequently interrupted or produce errors. For
this reason fax transmission via DSL telephony and G.711 is not supported. If the provider does
not support the T.38 protocol, then T.38 must be activated on the gateway. Otherwise the ISDN
must be used for the transmission. The number of potential fax connections at the same time
depends on the hardware used.
Use the WBM to switch from G.711 to T.38.
9.4.11 Dynamic Configuration Rules
9.4.11.1 Empirical Formula for Dimensioning
The current dynamic rules may be found on the intranet at:
http://intranet.mch4.siemens.de/syseng/perfeng/tools/hptindex.htm.
9.5 Static and Adaptive Jitter Buffer
The HG 1500 jitter buffer can be configured for the connection requirements of a specific net-
work.
Relevant WBM functions:
See Section 7.1.7, "Quality of Service"
See Section 7.7.5.5, "Editing DSP jitter settings"
9.5.1 Jitter Buffer Function
In TCP/IP-based networks, packets forming part of a single transmission can be sent at differ-
ent speeds. As this property can have a negative impact, especially on voice signal transmis-
sions, data stream manipulation is required. The jitter buffer is a cache memory for IP packets.
It can counter-balance IP packet delays to a certain degree.