Implementation suggestions

The results of our research are expected to have some impact on the development of explicit multi-path routing strategies. We hope that our investigation will provide some guidelines for future design of diversity-based multimedia transmission systems.

As for immediate use, except for cases where the application and the network is under the control of the same company, it will be too naïve to think that ISP routers can collaborate in any way with the end user streaming application. Also the existing streaming applications themselves are not assuming any engine for interfacing with the network routing (except probably the QoS flags).

Since changes of the routing of the physical network are restricted, we suggest obtaining capillary routing on overlay network using relay nodes or media routers [Nguyen03]. As a practically feasible application we can envisage relatively cheap UDP media proxy routers redirecting the UDP traffic on the application level. An ITSP, may collocate or host its media gateways in various network places, especially beneficiary is the hosting in premises of those ISPs who connects a noticeable numbers of the ITSP’s clientele. A hardware or software layer between the user streaming application and the network may be in charge of spreading the flow from the user agents (UA) to the destination, via the media gateways. The media gateways can be combined with the functionality of SIP (Session Initiation Protocol) servers or proxies. The UA layer can be implemented in the firmware of a SIP phone, in the NAT router of the user or in the closest SIP proxy.

Spreading can be obtained at a lower network layer, still controlled by end user and ITSP. ITSP can use VPN tunnels to spread the communication footprint. The flow at the source can be split across various VPN virtual interfaces. Since the VPN servers, forming an overlay network, are scattered, the flow of encapsulated packets will necessarily follow a wide footprint until is reached the VPN servers. Further, once the packets are released by the VPN servers to the open internet, the flow will be routed to the destination, still following a spread footprint.

Finally the ISP, if wishes to be real-time media tolerance friendly, can structure the routing of its network to be statically spread. Most routers, including all recent IOS releases of Cisco, provide packet level spread routing, EIGRP or balanced static routing. To combat packet loss along unreliable paths it is advisable also to use EIGRP in the packet load balance mode instead of the session load balance mode.