Assured Forwarding (AF): Extend the idea of RIO scheme

1. Assured Forwarding (AF): • Extend the idea of RIO scheme • Service profile specifies the expected capacity • Boundary nodes mark packet as in or out of profiles • During congestion, out packets are drop first. • The network should be provisioned to have sufficient capacity for in packets. • Four forwarding classes, each with three drop precedences. • Each class have a minimum amount of buffers and bandwidth. • A DS node should implement all four AF class, at least two of the three drop priorities. • The resources for each class should be configurable.

2. Assured Forwarding (AF): • AF PHB codepoints class 1 class 2 class 3 class 4 LOW 001010 010010 011010 100010 Medium 001100 010100 011100 100100 High 001110 010110 011110 100110 • Implementation guideline • A bandwidth partition between classes (WFQ) and drop priotities with a class • E.g: minimum bandwidth 2Mbps, 4 Mbps, 8 Mbps, 16 Mbps, Link would need 30Mbps, four queues with weights 1,2 , 4, 8.

3. Implementation guideline • Properties for the drop mechanisms • Minimize long-term congestion while allowing short-term fluctuation • Drop mechanism should drop packets from flows of the same long-term characteristics with equal probability. • Drop rate must be proportional to the flow;s percentage of the total traffic • Gradual discard • Relation between AF group and other groups • Not specified • Relationship be configurable and • Any PHB groups that can preempt any AF PHG group • How excessive resources are allocated

4. AF Service example • Need provisioning • Expected bandwidth service (RIO) • Two Codepoint with one for the four AF classes. • Several services with different provisioning level • Map different services to different class of PHBs

5. Expedited Forwarding (EF) • Low loss, low latency and assured bandwidth service. • A forwarding treatment for a traffic aggregate where the departure rate of the aggregate’s packet from any DS node must equal or exceed a configurable rate. • Can preempt other traffic • Simple priority queuing • Codepoint 101110 • Implementation guideline • Simple priority queue with a token bucket.

6. Packet classification • Divides an incoming packet stream into multiple groups. • Behavior aggregate (BA) or multifield (MF) • BA classifies packets based on the DSCP field. • MF uses one or more of the five-tuple • Can support more complex policies, marking packets based on application types, marking packets based on particular source and destination address, etc. • Multidimensional range matching • Requirement: speed, scalability • Algorithms: geometric approach and trie approach

7. Traffic policing • Metering and marking • Use token bucket. • Dual token bucket algorithm • Two regulators P and C, P is regulated by peak information rate (PIR) and peak burst size (PBS), C is regulated by committed information rate (CIR) and commited burst size (CBS) • Green if a packet passes the tests of P and C • Yellow if a packet passes P but not C • Read if a packet failed both tests

8. PIR: Peak information Rate PBS: Peak Burst size CIR: Committed Information Rate CBS: Committed Burst Size pkt_size: packet size pkt_arrival: arrival time of previous packet p_tk: the token counter for bucket P c_tk: the token counter for bucket C Token calculation: elapse_time = time_now() – ptk_arrival; p_tk = min[(p_tk+elapsed_time * PIR), PBS]; c_tk = min[(c_tk+elapsed_time * CIS), CBS]; pkt_arrival = Time_now()

9. If p_tk < pkt_size then mark the packet as RED Else if c_tk < pkt_size then mark the packet as YELLOW p_tk = p_tk – pkt_size; else mark the packet as GREEN p_tk = p_tk – pkt_size; c_tk = c_tk – pkt_size; End if