3. Integrated Services and Differentiated Services:- A Comparison

 
 
1.Scalability This issue is based on the characteristics of the flow state of both the architectures. While Int-Serv maintains a per-flow basis on the packets, Diff-Serv concentrates on aggregated flows. Due to this reason, Diff-Serv can create connections between DS compliant and DS non-compliant domains in addition to connections between DS compliant domains. This increases scalability.
2.Flow-State & Per-Hop Behavior  Int-Serv uses a 'soft-state' flow in it's per-flow signaling, in which there is periodic expiration of resource reservations. Whereas in the case of Diff-Serv there is no 'soft-state'. It concentrates on aggregated flows and Per-Hop Behaviour (PHB).The  PHB is implemented in the routers inside the Diff-Serv compliant domain, which provides the routers to monitor all the packets traversing their path so that they adhere to the Service Level Agreements.  
  
 
3.Resource Allocation Int-Serv uses the RSVP in order to allocate the required bandwidth for the path. Diff-Serv implements the marking, metering, shaping, and policing of packets and based on these criteria working  in conjunction with the DSCPs the required banwidth is allocated to each packet. 
4.Signaling With regards to signaling, Int-Serv uses a point-to-point signaling since it has to maintain per-flow soft-state. At the same time Diff-Serv cannot support an end-to-end QoS arhcitecture all by itself.  
  
 
5.Implementation(Deployment) Classification, marking, policing, and shaping are to be implemented only on the ingress and the egress routers only.Hence it can be deployed in a less harder way as compared to Int-Serv which deals with the fact that there is a per-flow soft state to be maintained and the timer also has to be taken into consideration henec it is a bit cumbersome. 
6.Backward Compatility The Diff-Serv architecture supports the backward compatibility, by reserving the first 3 bits of the IPv4 ToS octet. With this set-up, a DS compliant domain and connect to a non-DS compliant domain. Int-Serv doesn't have any such setup.  
  
 
7.Transmission Technology  Int-Serv implements the RSVP which supports multicasting, whereas the Diff-Serv architecture does not support multicasting because a multicast packet after arrival may exit from the DS domain from multiple DS egress nodes which enter multiple downstreams. So keeping the SLA legal and not violating it for the down stream nodes is difficult. 
8.Utilization  The last point is more of incorporating both the architectures under one   
roof. A DS domain can support a Int-Serv architecture inside it's domain.This is particularly useful because since Int-Serv supports multicasting and hence it is helpful for the DS architecture also. This sort of a combination helps both the architectures in maintaining Quality of Service.