Quality of Service
BAT54-Rail/F..
Release
7.54
06/08
9.4
Reducing the packet length
319
The FTP transfer uses quite large data packets of 1500 byte, whereas, the
Voice over IP connection sends packets of e.g. 24 byte net in relatively short
intervals. If FTP packets are in the sending queue of the BAT just at the mo-
ment when a VoIP packet is to be transferred, then the VoIP packet can only
be sent after the line is free again. Depending on the transfer rate of the con-
nection, this may cause a noticeable delay of the speech transmission.
This annoying behavior can be compensated if all data packets, which are
not belonging to the connection preferred by QoS, do not exceed a certain
packet length. While doing so, the data packets of the FTP connection will be
divided into such small sections that the time-critical VoIP connection is able
to deliver the packets without noticeable delay within the required time slots.
A resulting delay has no disadvantageous effect to the TCP-secured FTP
transfer.
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