ent MMSCs there is a need to calculate the traffic. In the case of different PLMNs, inter-MMSC traffic can be assumed as one of the components of the overall GPRS roaming traffic, depending of course on the roaming agreements in place. Inter-MMSC traffic can be provided through an SMTP protocol. The interconnection can be carried out also through the Internet, although VPN or at least some type of tunnelling protocol must be used, as MMS NETWORK PLANNING mentioned in section B.2. The dimensioning of the inter-MMSC traffic can be worked out as a traditional Excel-based exercise through the estimation of usage patterns, in a similar fashion to the SS7 connectivity requirements for inter-PLMN SMS dimensioning. In the early stages of deployment, with low traffic volumes, it should not be a bottleneck for the end-user experience. B.4 EFFECT OF MMS ON GPRS/GSM NETWORKS This section gives a general overview of the effects of MMS deployment in the existing network infrastructure. The effects can be described at two different levels: connectivity and traffic. Traffic impact is the major concern, since MMS data should not adversely affect the existing voice, messaging and packet data services. This section provides a first approach to the problem, and hints for analysis. Radio Network From the radio access point of view, MMS utilises the GPRS bearer. The dimensioning of the GPRS traffic for the air interface should include the MMS forecasts, or it should be modified to include them. It is not expected to have a great impact in the early stages, since traffic volumes should not be excessive while the penetration is low, and since the nature of the MMS traffic allows a certain delay without affecting the end-user experience. Thus, it can be considered as additional packet data traffic. Cellular Transmission Network From the cellular transmission point of view, the MMS traffic does not add concerns, other than a revision of the dimensioning and checking of the spare capacity of the links against the traffic growth forecasts o