An End-to-End Service Architecture r Provide assured service, premium service, and best effort service (RFC 2638) Assured service: provide reliable service even in time of network congestion r SLA specifies the rate and burst size for assured traffic r Customer decides how the applications share the bandwidth

Assured Service: Leaf Router Functionality r Leaf router: the router directly connected to a host in a customer network r Leaf routers configured with the traffic profile (rate and burst size) for assured flows r Leaf routers perform classification (based on packet header) and marking on arriving packets before forwarding them. r Marking: m A token present: packet considered as in profile, A-bit set to 1 m A token not present: packet considered as out of profile, A-bit set to 0

Assured Service: Leaf Router Functionality Marker function

Assured Service: Queue Management r All packets are put into an Assured Queue (AQ) managed by RIO (RED with In and Out) r RED (Random Early Detection): discarding packets before buffer space is exhausted m Router maintains a running average of the queue length m When the average queue length exceeds a threshold, pick a packet at random and drop it  TCP flow control mechanisms at different end hosts will reduce send rates at different time. r RIO: two thresholds t1 an t2 for each queue. m When the queue length L < t1, no packets are dropped m When t1 < L < t2, only out packets are randomly dropped m When L > t2, both in and out packets are randomly dropped, but out packets are dropped more aggressively.

Premium Service r Provide low-delay and low-jitter service r The SLA specifies a peak rate for premium traffic r Customer responsible for not exceeding the peak rate: excess traffic will be dropped. r Customer decides how the applications share the bandwidth r Desirable for ISPs to support both static SLAs and dynamic SLAs. m Admission control needed for dynamic SLAs.

Implementation of Premium Service r The leaf routers perform classification and marking. r Marking: m Token present: packet has P-bit set m No token present: packet held until a token arrives (shaping) m Token bucket depth limited to one or two packets  create very regular traffic patterns and small queues. r All packets with the P-bit set enter a Premium Queue (PQ). m Packets in the PQ sent before packets in the AQ. r The exit routers of the customer domain may reshape the traffic to ensure that the traffic does not exceed the peak rate specified by the SLA. r Need Limit the total bandwidth requested by Premium traffic. Why?

Premium Service: Leaf Router Functionality Marker function

Border Router Functionality r The agreement between adjacent administrative domains specify a peak rate on P traffic and a rate & burst for A traffic r A Profile Meter (constructed from a token bucket) is required at the border routers of an ISP to ensure that packet flows are in compliance with their agreed-upon rates & burst sizes. m Non-compliant packets of Premium flows are discarded m Noncompliant packets of Assured flows have their A-bits reset. r Each input interface at a border router has its own profile meter corresponding to a particular class across the boundary.

Profile Meter at Border Router

Service Allocation in Customer Domains r Service allocation: deciding how the hosts in a customer domain share the services specified by the SLA r Bandwidth broker (BB) used to allocate resources in a customer domain r Before a host starts sending packets, it sends a message to BB to request for desired service m A request includes a service type, a target rate, a maximum burst, and the time period when service is required. m BB checks if there is sufficient bandwidth to meet the request m If BB grants the request, it sets the classification and marking rules at the leaf router directly connected to the sender r Dynamic SLA: BB must use a signaling protocol (e.g., RSVP) to request resources on demand from the ISP.

Resource Allocations in ISP Domains r Given the SLAs, ISP must configure the border routers with the classification and policing rules r Static SLA: border routers are manually configured r Dynamic SLA: m BB in customer domain sends a PATH message to BB in its ISP m BB in ISP makes an admission control decision Grant: send PATH message to BB in the destination domain Deny: send back error message m If BB in destination domain accepts the request, it configures its border router and sends RESV message back to BB in the ISP m When BB in the ISP receives the RESV message, it configures the border router and sends RESV to BB in customer domain m When BB in the customer domain receives RESV, it configures the leaf router

Uneven traffic r by admission control, the amount of premium traffic can be limited to a small percentage (say 10%) of the bandwidth of input links. r excess packets are dropped at the ingress routers of the networks  Non-conformant flows cannot impact the performance of conformant flows. r premium packets are forwarded before packets of other classes  they can potentially use 100% of the bandwidth of the output links. r if premium traffic is distributed evenly among the links, these three factors should guarantee that the service rate of the PQ is much higher than the arrival rate  The delay or jitter experienced by premium packets should be very low.

Uneven traffic r uneven distribution of premium traffic may cause a problem for Premium Service. aggregation of premium traffic in the core may invalidate the assumption that the arrival rate of premium traffic is far below the service rate. r Differentiated Traffic Engineering/Constraint Based Routing must be used to avoid such congestion caused by uneven traffic distribution.