1 Routing as a Service Karthik Lakshminarayanan (with Ion Stoica and Scott Shenker) Sahara/i3 retreat, January 2004

2 Problem Applications demand greater flexibility in route selection –Resilience: RON, Tapestry –Performance: Detour Applications need different routing functionality –Multicast: ESM, Overcast –DDoS defense: SOS, Mayday –Anycast: Gia Difficult to change any routing-level component in the Internet today!

3 Current approach Overlay networks –Layer above IP –Deployability Problems: –Ossification: overlay solutions again ossify routing in the protocol; hard to modify once deployed on large scale (lessons from the Internet) –Efficiency: replicate packets multiple times along a physical link; inefficient route construction –Lack of control for ISPs: traffic hard for ISPs to control; circumvent ISPs’ policies

4 Routing in transportation network Multiple route providers

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6 Multiple route metrics

7 Time taken Distance

8 Our thesis Push routing out of infrastructure Argument for “edge-controlled” routing –Related: NIRA (NewArch group, MIT/ISI) Our contribution: –Fine-grained control over routing –Control plane for achieving this

9 System architecture 1.Forwarding infrastructure –Provides basic routing (referred to as default routing) –Exports primitives for inserting routes

10 System architecture 2. NEWS/Route selector –Aggregates network information –Selects routes on behalf of applications NEWS-1 NEWS-2 Network information Performance-based, policy-based routing (span multiple ISPs)

11 System architecture 3. End-hosts –Queries NEWS to setup paths NEWS-1 NEWS-2 Network information Query/reply routing info. Setup routes Client A Client D Client B Client C

12 Architectural position Separate control plane and data plane by using clean abstractions Host Infrastructure Internet & Infrastructure overlays Data plane Control plane P2P & End-host overlays Data plane Control plane Our proposal Data planeControl plane

13 Challenges Open, multi-provider system (design of primitives) –Unlike intra-domain, e.g. GSMP –Security: control provided should not be used for attacking the system –Trust: between entities of the system, e.g. what information does system give to NEWS Large-scale system (route selection) –Scalability: monitoring; service to end-hosts –Stability: should not lead to oscillations Deployability: ISP control

14 Infrastructure primitives Label-switching-like primitive –Allows insertion of forwarding entries (id 1, id 2 ), where id 1, id 2 are labels –id = [ NodeID : LocalID ] Establishing paths – Loose virtual path (LVP) –Composition of label switches: T = (id 1, id 2, …, id n ) is composed as (id 1, id 2 ), …, (id n-1, id n ) –Construct different topologies –Aggregation can be performed at the level of tunnels that end at infrastructure nodes

15 1. Trust Infrastructure provides network information to NEWS Network infrastructure NEWS Verification: NEWS should be able to verify this –Indirect measurement techniques using primitive alone –Metrics: Delay, loss, bandwidth

16 1. Trust NEWS provides routes across the network Network infrastructure NEWS Client C Verification: Network verifies correctness

17 2. Scalability Monitoring: –Monitor a subset of links –Update period depends on stability (exploit link stationarity) For e.g., updates can be sent when metric on the link changes by a factor of x Computation: –Incremental computation of best paths –Multiple paths are returned Querying: –Default paths are used if special routing is not needed –Hierarchical dissemination –Caching of results: TTL chosen to reflect stability of paths

18 3. Deployment Infrastructure nodes –Hosted at certain points within ISPs NEWS/Route selection –3 rd party provider like Akamai –Few in number –Determined by application requirements Trust relations –NEWS trusts infrastructure for information (verifiable) –ISPs trust paths that NEWS returns (verifiable) –Export links that obey the underlying policy constraints

19 Implementation status i3 primitives for setting up forwarding state Distributed NEWS implemented –Route computation based on delay, loss and bandwidth –Deployed on PlanetLab i3 proxy has been modified to query NEWS –Legacy applications can be used with NEWS

20 Summary of results Verification of measurement techniques –Delay: 97% of cases have error < 10% –Loss-rate: 90% in over 80% of the cases –Bandwidth: Within a factor of 1.5 in 60% of cases Scalability of monitoring –Simulation-based –Logarithmic-degree graph –Achieve 90% RDP of 2.3 (for delay) for TS-16384

21 Summary Routing control pushed outside the infrastructure Routes computed by third-party entities (NEWS) along with measurement information provided by the infrastructure Leads to “evolvable” networks –Deploy new routing schemes or optimize existing routing without changing the infrastructure