1. Differentiated Services for the Internet Selma Yilmaz

2. Current paradigm Same type of service to all traffic Goal Give better service to some applications Why? some applications need it, such as voice and video some users need better traffic control, such as ISPs will lead to healthy economic and service environment

3. Idea Combine two existing schemes: Assured service and Premium service Use one bit of IP header for service differentiation Bandwidth is a resource that is being requested and allocated Allocate bandwidth to different users in a controllable and predictable way during the network congestion Keep complexity to edges Keep forwarding path simple

4. Assured Service (Expected capacity framework ) better best effort Define a service profile for each user: –Traffic specifications what is provided to the customer (ex: 5Mbps average throughput) –Scope to where this service is provided (ex: specific destination, group of destinations ) -Probability of assurance level of assurance of the provided service Monitor the traffic of each user as it enters the network

5. Assured Service (cont.) Tag packets as In or Out of their service profiles (Profile meter) At each router, if congestion occurs, preferentially drop packets whose tag is Out (RIO) The packets of all users are aggregated into one queue BUT different users have different quantities of In packets depending on their profile

6. Assured Service (cont.) RIO: Random Early Drop Gateways with In/Out bit Discriminates against Out packets in times of congestion Uses twin RED algorithms: one for Ins and one for Outs P(drop-in) min_in max_in 1 P(drop_out) 1 avg_in avg_total min_outmax_out 1) min_out<min_in 2) Pmax_out>Pmax_in 3) max_out<max_in Pmax_in Pmax_out

7. Does not describe a strict guarantee The assurance that user gets: Assured service traffic flow is unlikely to be dropped as long as it stays within the profile. Excess traffic does not have the same assurance level Assured Service (cont.)

8. Premium Service (Virtual Line) Service levels are specified as a desired peak- bit-rate for a specific flow The user contract with network not to exceed the peak rate Network contract with user the contracted bandwidth will be available when traffic is sent

9. Premium Service (cont.) H9 H8 H7 Leaf 2 H4H5H6 H3H2H1 Leaf 3 Leaf 1 Border router ISP border router Egress point Ingress point A trust region Policies marked aggregate traffic to purchased amount, discard excess amount

10. Premium Service (cont.) First-hop routers has been configured to match a flow from host’s and destination’s IP address set P-bit of flows that match a premium service specification do traffic shaping to smooth bursts before they enter the network Routers along the path (within an intranet) use two levels of priority queuing and send marked packets first

11. Adjacent administrative domains have agreement on packet rate of aggregate P-traffic and discard packets that exceed the rate An egress border router may do some reshaping on aggregate premium traffic to conform the rate agreed upon An ingress border router drop the packets that are exceeding the rate (token bucket) Premium Service (cont.)

12. Two-bit differentiated services architecture There is demand for both services Not conflicting each other Allow both services together: A-bit, P-bit in IP header Design Constraints - Scaling Push all the state to the edges Force all per-flow work to the edges (like shaping and policing) Premium Service (cont.)

13. Leaf router input functionality Packet classifier – which packet belongs to which flow based on IP header Marker –configured from usage profile for that flow –service class (P/A), peak rate for P and rate –permissible burst size for A Packet classifier Clear A & P bits Arriving packets Best-effort Marker 1 Marker N Forwarding Engine Flow 1 Flow N Premium Service (cont.)

14. Markers to implement the two different services Token bucket fills at the flow rate specified in usage profile For a premium flow, marker will hold packets when necessary to enforce their configured rate (Packets may be dropped) Wait for token Set P bit Packet input Shaped traffic Packet input Test if token Set A bit Token No token (Out profile) Burst size Premium Service (cont.)

15. Router output interface P-bit set ? yes no High-priority Low-priorityIf A-bit is set, A_count++ RIO queue management If A-bit is set, A_count-- Packets out Must have two queues: Service premium packets first Premium Service (cont.)

16. Inter-domain traffic Agreement between adjacent administrative domains must specify –peak rate for all P traffic –rate and burst for A traffic Profile meter at the ingress of a trust region enforces the rates by using token bucket

17. Border router input interface Profile Meters Arriving packet Is packet marked? Token available ? Token available ? Drop packet Clear A bit Forwarding engine Not marked P set A set No Token No Premium Service (cont.)

18. Discussion Shapers are at the edge of the network: Per flow state info is at the edge Routers internal to a trust region do not need to do traffic shaping priority queuing and preferential drops Border routers may need/desire to do shape the aggregate flow of marked packets at egress Premium Service (cont.)

19. If these services becomes insufficient, add other kinds of service levels: –More queue levels can be added for P-traffic, more drop priority levels may be added to A bit traffic What if after implementing an architecture for both services, experience shows that only one is needed? –Unnecessary implementation cost Premium Service (cont.)

20. How to allocate the level of marked traffic? Allocation: process of making marked traffic commitments “Per-call” dynamic set up Good resource efficiency, poor cost control Pre-configuring of usage profiles Good cost control, bad resource efficiency Both are extremes –Aggregate demand can always be split into two components: predictable and exceptions Premium Service (cont.)

21. Bandwidth Brokers (BB) Repository of a policy database that keeps the information who can do what and when within a trust region Only BB can configure the leaf routers If dynamic allocation is possible, each adjacent domains’ BB negotiate and configure the rate and a service class (P/A) across the shared boundary Premium Service (cont.)

22. H9 H8 H7 Leaf 2 H4H5H6 VH3H2H1 Leaf 3 Leaf 1 Border router ISP border router BB BB setting profiles in Leaf Routers

23. H9 H8 H7 Leaf 2 H4H5H6 VH3H2H1 Leaf 3 Leaf 1 Border router ISP border router BB V:4 to D:8 P@128kb/s 1pm-3pm signed:V

24. BB setting profiles in Leaf Routers H9 H8 H7 Leaf 2 H4H5H6 VH3H2H1 Leaf 3 Leaf 1 Border router ISP border router BB V:4 to D:8 P@128kb/s 1pm-3pm signed:V V:4>d:8 P@128kb/s Classifier Rate Type V:4>D:8 128kb/s P

25. End-to-end example with static allocation LBL ESNet NEARNet MIT BB V D 10 kbs to D ok 100 10 to D 1050 ok Peer Policy Total Used NearNet ask 10 10 LBL <50 ok 100 30 Peer Policy Total Used ESNet ask 0 0 MIT <50 ok 50 20

26. References A Two-bit Differentiated Services Architecture for the Internet K. Nichols, V. Jacobson, L. Zhang Explicit Allocation of Best Effort Packet Delivery Service D. Clark, W. Fang