Differentiated services
This continues from the previous post on IntServ. DiffServ tries to address the difficulties with IntServ. For example, if the routers all keep track of the per flow reservations, then they don't scale when the number of flows is high such as in the case of high speed networks. Also, Diffserv is able to provide bands of service because the network as a whole makes the decisions. The edge routers decide what service model can be met. This simpler service description is signaled through the network with a method simpler than the RSVP. The packets are labeled with a priority stamp. With these labels, the core of the network finds it easy to forward packets instead of the per flow states that was being maintained. Therefore the network provides expedited services instead of best effort an d is an incremental improvement over the existing networks.
Moreover, the service providers can define and implement any forwarding behavior on top of this architecture. So service providers can differentiate their services. The architecture supports QoS by aggregating flows and yet allows service providers to implement per-flow Scalability and differentiated services are the two important advantages of this design.
Diffserv
The edge router performs the admission control functions such as classification, metering, marking and conditioning. Classification determines the labels based on rules. Metering checks whether the traffic can be accomodated. Marking marks packets with their labels. Conditioning regulates the traffic even discarding if forwarding is not possible.
The markings are based on Type of Service in IPv4 and traffic class in IPv6.
The core routers perform only forwarding according to "Per-Hop-Behaviour" depending only on the labels. Thus the core routers are stateless. The Per-hop-Behaviour is what service providers can dictate.
This continues from the previous post on IntServ. DiffServ tries to address the difficulties with IntServ. For example, if the routers all keep track of the per flow reservations, then they don't scale when the number of flows is high such as in the case of high speed networks. Also, Diffserv is able to provide bands of service because the network as a whole makes the decisions. The edge routers decide what service model can be met. This simpler service description is signaled through the network with a method simpler than the RSVP. The packets are labeled with a priority stamp. With these labels, the core of the network finds it easy to forward packets instead of the per flow states that was being maintained. Therefore the network provides expedited services instead of best effort an d is an incremental improvement over the existing networks.
Moreover, the service providers can define and implement any forwarding behavior on top of this architecture. So service providers can differentiate their services. The architecture supports QoS by aggregating flows and yet allows service providers to implement per-flow Scalability and differentiated services are the two important advantages of this design.
Diffserv
The edge router performs the admission control functions such as classification, metering, marking and conditioning. Classification determines the labels based on rules. Metering checks whether the traffic can be accomodated. Marking marks packets with their labels. Conditioning regulates the traffic even discarding if forwarding is not possible.
The markings are based on Type of Service in IPv4 and traffic class in IPv6.
The core routers perform only forwarding according to "Per-Hop-Behaviour" depending only on the labels. Thus the core routers are stateless. The Per-hop-Behaviour is what service providers can dictate.
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