Cpr E 458558 RealTime Systems RealTime Networks WAN

Cpr. E 458/558: Real-Time Systems Real-Time Networks – WAN Channel establishment Cpr. E 458/558: Real-Time Systems (G. Manimaran) 1

Qo. S metrics: types of constraint Metrics and their nature • End-to-end delay: additive metric, path metric • Delay jitter: additive metric, path metric • Bandwidth: convex (min), link metric • Packet loss: multiplicative, path metric Theorem: A problem with two or more path constraints is NP-Complete, assuming the constraints are independent and the values are real. Cpr. E 458/558: Real-Time Systems (G. Manimaran) 2

Qo. S routing problem instances Given a graph G(V, E), with each edge labeled with (cost, delay, available bw). • Bandwidth-constrained least-cost routing – Polynomial time problem – Solution: Remove edges that don’t satisfy BW constraint and then run shortest path algorithm on the reduced graph. • Delay-constrained, BW-constrained, least-cost routing – NP-complete problem – Heuristics exists Cpr. E 458/558: Real-Time Systems (G. Manimaran) 3

Channel establishment – Qo. S routing • Source Routing – Source computes the routing path – Obtaining global state is difficult – Not scalable • Distributed Routing (hop-by-hop) – Each node decides what is the next hop – Lack of global knowledge inferior paths – Scalable • Hierarchical Routing – Based on aggregate state information – Scalable (works well for inter-domain routing) – Compromise between source and distributed routings Cpr. E 458/558: Real-Time Systems (G. Manimaran) 4

Choose the Source Routing entire path from source to destination Connection 1 S 1 D • The source has the entire network state information (cost, delay, etc. . of each edge) Cpr. E 458/558: Real-Time Systems (G. Manimaran) 5

Distributed / Hop-by-hop Routing Connection 1 S 1 D Cpr. E 458/558: Real-Time Systems (G. Manimaran) 6

Hierarchical Routing S D Cpr. E 458/558: Real-Time Systems (G. Manimaran) 7

Hierarchical Routing 1 S based on precise state Routing based on aggregate state Routing based on precise state D Cpr. E 458/558: Real-Time Systems (G. Manimaran) 8

Qo. S Source Routing Choose the path from Connection 1 With some S Qo. S requirements 1 source to destination that satisfies the Qo. S requirements based on some heuristic function D • The source has the entire network state information (cost, delay, etc. . of each edge) Cpr. E 458/558: Real-Time Systems (G. Manimaran) 9

Qo. S Hop-by-hop Connection setup Connection 1 With some S Qo. S requirements 1 No outgoing edge satisfies the required Qo. S Therefore, back off D Cpr. E 458/558: Real-Time Systems (G. Manimaran) 10

Channel establishment – Resource reservation • Once a feasible path is found, resources such as bandwidth, buffers are reserved along the path • Resource Reservation Protocol (RSVP) – Receiver-driven protocol – Supports multicast as well as unicast – Provides different type of reservation styles Cpr. E 458/558: Real-Time Systems (G. Manimaran) 11