2 1.Why traffic shaping? Network knows what traffic to expect Network can determine if the flow should be allowed to sendNetwork monitor the flow’s traffic - confirm the flow’s behavior as promised
3 1.Why traffic shaping? 1. Regulating traffic - 100 MB / 1 s vs 1 KB / 10 µs2. Deciding weather to accept the flow’s data- can buffer 100 MB ?3. Policing a flow- detect misbehaving flows
4 1.Properties of good traffic shaping scheme Shaping scheme should describe wide range of schemesShaping rules should make it easy to describe traffic patternsShaping scheme should be easy to police
5 regular amounts of data emitted at regular intervals 2. Isochronous Shapingregular amounts of data emitted at regular intervals
6 2.1. Simple Leaky Bucket Each flow has its own bucket send rate ρbucket size βCell & datagram trafficEasy to implement & to describe.ex: FIFO + Timer
7 2.2. (r,T) Smooth Traffic Based on stop and go algorithm Send no more than r bits in any T time periodLimitation 2r sized datagram can’t be sentImplementation -simpleBit counter, refreshed every T bit times
8 2.3. Limitations of Isochronous Shaping Easy to implementEasy description & traffic policingThe range of behavior limited to fixed rate data flow. Var. rate flows request the peak rate -> wasting network capacity - peak values occurs rarely
9 3. Isochronous Shaping with Priority Schemes Uses bit patterns for priorityHow prioritizing is done:application: knows less important datanetwork: marks the incoming cells at exceeding rates
10 3. Isochronous Shaping with Priority Schemes Limitations of priority schemes:low priority packets don’t get throughbandwidth reservation for low priority trafficselectively discard packetsmany com. devices uses FIFOs - continuous memory~ sufficiently flexible~ used in first generation cell switches
11 4. Shaping Bursty Traffic Patterns Token BucketToken Bucket with Leaky Bucket Rate Control
12 4.1. Token Bucket Tokens inserted at rate ρ into bucket if bucket is full -> token is droppedsend allowed if there are b tokens in bucket, b*size ≥ packet-sizeβ+τ/ρ tokens worth data at any τ time intervallong term transmission rate is ≤ ρ
13 4.1. Token bucket - limitations No need for discard & priority policydiscards tokens and leaves to the flow the managing transmission queue if the flow overdrives the regulatoreasy to implement (counter + timer)policing -> bit more difficult - possibility for cheating in data rate
14 4.2. Token Bucket with Leaky Bucket Rate Control ρToken bucketßLeaky bucketcdataß
15 4.2. Token Bucket with Leaky Bucket Rate Control Token bucket combined with a simple leaky bucketC >> ρbehaves like token bucket:permits bursty traffic - but regulates max. traffic to rate Clong term transmission rate is ρ
16 5. ConclusionsMore accurate description of flow’s rate help network to effectively manage its resourcesSimplest shaping - leaky bucket - for fixed data ratespriority schemes - more general, combines H/L priority traffic in the same flowtoken bucket (with leaky bucket) -> more diverse traffic patterns
18 Flow Setup and Routing The Host’s role in flow setup Protocols to establish a flow - ST IIRouting - Multicasting flow
19 1. The Host’s role in flow setup Some mechanism/ protocol/data structure needed to ask the network for particular performance guaranteesTwo main ways:few variables identify a general class of req.video, voice, big file transfer flowsrouters preconfigured - new apps -> new classesmultivalued explicit specification of flow spec.bustiness, delay requirements, sensitivity to loss etc.
20 2. Network answers to requests Three main modes:simply yes / no answerestablish the best service available currently - if the best case is not acceptable the application can end the flownegotiations should be interactive - complexity at network & application
21 3.Protocols to establish a flow General requirements:setup protocol should accommodate multiple receivers for a single flowset up flows quicklyresult in robust reservationschange the flow properties after flow is establishedsupport advance reservations
22 3.1. Strawman proposalEnhance an existing internet protocol like IP by adding a flow ID field, and a flow spec option that can be sent as part of IP headerRouters forward IP datagrams as before, only if flow id is set forward based on information about flow requirements.If has no info forwards normally & ask sender for information
23 3.2. Version 2 of the Stream Protocol Most sophisticated / complex /complicated flow setup protocolTwo protocols:a datagram forwarding protocol STconnection management protocol ST Control Message Protocol SCMP17 SCMP messagesflow setup is done hop-by-hop
24 3.3. RSVP Resource ReSerVation Protocol not the sender is managing the flow but each recieverfilters are used:provide support for heterogeneity - receivers with slow links still can participate on flowsdynamic filtering allows receivers to modify flow properties - switching btw. listening of A and Btry to reduce load & improve bandwidth management.
25 4. RoutingHistorically routing: determining if path exists btw. two points in a networkRouting supporting flows (more difficult): determining if a path exists so to achieve a flow’s requirement
26 4.1. Routing Bellman-Ford Dijkstra’s alg. tries to minimize routing information by requiring routers to pass along information only about best routesImplemented in: RIPDijkstra’s alg.distributes complete routing information to all routing agentsImplemented in: OSPF, IS-IS
27 4.2. Multicasting and Multiobjective Routing not only finding a path but finding a delivery treesender or receiver based routing ?Q.E.D.
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