2.1.1 Integrated Services Model



According to  RFC1633, the Int-Serv model focussed on real-time traffic and the two sorts of service associated with is guaranteed and predictive service.This will integrate with the controlled-link sharing class of service.This is carried out keeping in mind about certain key assumptions:

i) bandwidth (resources) must be explicitly managed in order to meet application requirements, implying that 'reservation of resources' and 'admission control' are fundamental blocks of this service.

ii) also, in general, stricter guarantees have a higher cost in resources that are made unavailable for sharing with others.

But at the same time certain resource guarantees cannot be accepted and hence cannot be  incorporated in the list of assumptions.These arguments are:

i) bandwidth will be infinite:- this is not acceptable in the present state of affairs because it cannot be that bandwidth becomes ubiquitous to such an extent that it can be wasted. Atleast not in the proximate future. Also that even if it becomes cheap and commonly available, it will not be available throughout the Internet. New applications will always be invented to consume the bandwidth leading to congested links again.

ii) simple priority is sufficient:- premium services require that they receive higher priority than the others because they pay more for a better share of the bandwidth. But priority is an implementation technique and not a service model.It can be implemented but we cannot just get the exact features that we want.In case of simple priority, the issue is that as soon as there are too many users, then every stream will be degraded.

iii) applications can adapt:- the development of adaptive real-time applications does not eliminate the need to bound packet delivery time. Human requirements for interaction and  intelligibility limit the possible range of adaptation to network delays. The users find that interaction is impossible in these cases.

An important assumption that needs to be added is that it is desirable to use the Internet as a common infrastructure to support both non-real time and real-time traffic and inadvisable to have a parallel infrastructure which is just for real-time services because it would lose the significant advantages of statistical sharing between real-time and non-real time traffic.

2.1.2 Reference Implementation Framework:-
The Reference Implementation framework is used to realize the Int-Serv model.This framework includes four components:
a) The Packet Scheduler.
b) The Admission Control Routine.
c) The Classification of packets based on the different Classes of Service (CoS).
d) The Resource Reservation Set-up Protocol (RSVP).