Resource management is about implementing various protocols to provide relative or guaranteed quality of service (QoS) in an Internet Protocol (IP) network (Figure 5.1).
Relative QoS is associated with the DiffServ model, for which the protocol is carried by the IP header. The initial ToS field in the IPv4 header is replaced by the DSCP (DiffServ Code Point) mark, which determines the behavior of the router. The marking is performed at a trusted piece of equipment (the switch, the router, or optionally the host station).
Guaranteed QoS is associated, for example, with the IntServ model, for which RSVP (ReSerVation Protocol) performs resource reservation. The resource, for which a request is generated by the terminal station, is set up at the routers through which user traffic goes. It should be noted that the resource is reserved after its availability has been tested.
One drawback of the IntServ model is lack of scalability. It is impossible to store status information relating to a large number of flows at the routers.
The ARSVP (Aggregate RSVP) protocol allows this difficulty to be partially solved by aggregating user requests going in a common direction. Request aggregation is performed by a router. The reservation request can be generated either at the terminal station or at the router.
The DiffServ model provides differentiated treatment ...