Reservations for Aggregate

Among its various uses, IP-in-IP tunneling is a simple way to aggregate the data ows from multiple sources to multiple destinations into one ow, to cross part of the Internet. In this paper we report our design and implementation of RSVP support for resource reservations over IP-in-IP tunnels, and our experience from this eeort that revealed a number of issues related to making resource reservations for aggregate data ows. First, aggregation and de-aggregation go in pairs, thus the exit point of the tunnel must have adequate information to be able to de-multiplex the aggregate tunnel reservation back to reservations for individual ows. Second , if multiple reserved sessions exist over one tunnel, the two tunnel end points need mechanisms to synchronize on which end-to-end reservation is bound to which tunnel reservation ; on the other hand mapping all reservations of the same traac class into one tunnel session can substantially simplify the protocol. Furthermore, one must also properly map error reports from the aggregate reservation back to the ends of individual ows. Many large corporations are moving their networking infrastructure away from leased lines to the public Internet, as a way of cutting down communication costs. Responding to this market demand, most nationwide Internet Service Providers ooer today Virtual Private Network (VPN) services. A VPN provides the illusion of a private network overlaid over the public Internet. In a VPN scenario, the company's sites are connected over the public Internet with virtual links called \tunnels". Packets that have to cross sites enter one end of the virtual link and are transported, through the common infrastructure, to the other end of the link. IP tunneling uses a simple encapsulation technique. The tunnel \entry" point adds an outer IP header in front of the original IP header of each packet, givning all intermediate routers an illusion that packets are delivered between the outer source and destination addresses. When the encapsulated packet reaches the tunnel exit point, the outer header is thrown away and the packet is further routed towards its nal destination. VPNs seem a prime environment for the deployment of QoS support (such as Integrated Services and RSVP 3]) since they support business critical applications and are replacing a more controllable environment (the private network created by leased lines). Using the current IP-in-IP encapsulation model, RSVP reservations are not possible. Since all the packets that reach one of the tunnel end-points …