substantially increase the header length the method of packet heading according to the invention for a mobile in a foreign network retains the advantage of shorter headers and higher payloads in common with the invention set out in the copending patent application no 99301437 2 referred to above since the ha address is used as the source address the problems caused during egress filtering by using a source address different from the home network address can be avoided since the destination address is changed back before a packet is delivered an application to which the packet is delivered does not need to be reconfigured so irritating stops and re starts of the application are avoided a further advantage is that only the source and destination addresses of the header are changed all other information is unchanged including information identifying the traffic flows from the ha 26 to the current coa of mn 28 it is therefore possible to adopt a standard qos arrangement such as rsvp without modification to provide qos services to the mobile a qos session will now be described using rsvp as an example in fig4 the cn 24 and ha 26 are associated with home network 50 and the mn 28 and fa 30 are associated with a foreign network 52 the rsvp session is set up as two parts shown as section.