1 / 41

Routing as a Service

Routing as a Service. Karthik Lakshminarayanan (with Ion Stoica and Scott Shenker) Sahara/ i3 retreat, January 2004. Problem. Applications demand greater flexibility in route selection Resilience: RON, Tapestry Performance: Detour Applications need different routing functionality

miguelwong
Download Presentation

Routing as a Service

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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. Multiple route providers Routing in transportation network

  5. Multiple route metrics

  6. Time taken Distance

  7. 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

  8. System architecture • Forwarding infrastructure • Provides basic routing (referred to as default routing) • Exports primitives for inserting routes

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

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

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

  12. 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

  13. Infrastructure primitives • Label-switching-like primitive • Allows insertion of forwarding entries (id1, id2), where id1, id2 are labels • id = [ NodeID : LocalID ] • Establishing paths – Loose virtual path (LVP) • Composition of label switches: T = (id1, id2, …, idn) is composed as (id1, id2), …, (idn-1, idn) • Construct different topologies • Aggregation can be performed at the level of tunnels that end at infrastructure nodes

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

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

  16. 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

  17. 3. Deployment • Infrastructure nodes • Hosted at certain points within ISPs • NEWS/Route selection • 3rd 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

  18. 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

  19. 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

  20. 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

  21. Backup slides

  22. m1 m1 m1 m R NEWS: Round-trip delay n1 n2 • Use path selection primitive to send packet m along R→n1→R • Use path selection in conjunction with packet replication to send packet along R→n1→n2→n1→R • Difference yields the RTT of the link (n1↔n2) To measure: RTT(n1→n2)

  23. m1 m1 m1 m2 m NEWS: Measuring loss rate n2 n1 • Forwarding links • (n11→ n21) • (n11 → R) • (n21 → n12) • (n21 → R) • (n12 → R) R To measure loss(n1→n2)

  24. m1 m1 m1 m2 m m R NEWS: Measuring loss rate n1 n2 • Forwarding links • (n11→ n21) • (n11 → R) • (n21 → n12) • (n21 → R) • (n12 → R) To measure: loss(n1↔n2)

  25. m1 m1 m1 m2 m NEWS: Measuring loss rate n2 n1 • m2 used to differentiate loss on (n1→n2) from that on (n2→n1) • (m Λ ~m1 Λ ~m2)  loss on virtual link (n1→n2) • False positives • False negatives • Probability of false positives/negatives ≈ O(p2 ) R To measure loss(n1→n2)

  26. 1 1 Bottleneck? 1 NEWS: Available bandwidth n2 n1 • Delay-based bandwidth measurement (TCP Vegas like) • Increase sending rate till increase in delay is seen cwd=1 cwd=2 cwd=4 R T = received time – sent time T’ = smallest RTT seen thus far

  27. 1 1 1 1 NEWS: Available bandwidth n2 n1 • Use packet replication to identify if the bottleneck is on (n1→n2) or not cwd=2 cwd=3 R T = received time – sent time

  28. 1 1 1 1 1 NEWS: Available bandwidth n2 n1 • Use packet replication to identify if the bottleneck is on (n1→n2) or not cwd=2 R T = received time – sent time

  29. 2 2 1 1 1 d 2 NEWS: Bottleneck bandwidth n2 n1 Packet-pair-like technique Bottleneck R

  30. 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 2 2 2 d d d1>d 1 1 1 NEWS: Bottleneck bandwidth n2 n1 • BBW = k*p/d1, where k = deg of replication • More the degree of replication, greater is the possibility of error • Intervening packets would affect this Bottleneck R

  31. 1. Trust • Problem: Verify network information (delay, loss, bandwidth) provided by the network • Partial trust relations between the third party (NEWS) that computes routes and the infrastructure • Solution: Ability to measure network characteristics using the simple label-switching primitive alone • Infrastructure cannot differentiate data packets and measurement packets

  32. 2. Security • Problem: To prevent construction of illegitimate forwarding graphs using the primitives (e.g. loops) • Implicit mechanisms: • Cryptographic constraints on successive forwarding labels (described in Secure-i3) • Protects against forming loops, confluences in the forwarding graph • Explicit mechanisms: • NEWS servers ensure that computed paths are legal • NEWS signs the paths that it returns • Infrastructure trusts NEWS and inserts the signed paths • Can verify the validity of the paths that NEWS returns

  33. NEWS-2 NEWS-1 Scalability • Multiple vantage points for measurements/monitoring • Maintain a subset of links • Division of overlay graph to reflect underlying paths

  34. NEWS-2 NEWS-1 Scalability 2-level hierarchy • Random partitioning of nodes into buckets • Maintain few edges within the same bucket • Maintain few edges to every other bucket • If bucket size is √N, each measurement point responsible for only O(√N) links

  35. Implementation status • i3 primitives are used as the infrastructure primitives • Distributed NEWS is implemented and can perform route computation based on delay, loss and bandwidth • i3 proxy has been modified to query NEWS • Legacy applications can be used with NEWS

  36. Evaluation • Effectiveness of indirect measurements • Planetlab experiments • Scalability techniques

  37. NEWS: Delay Estimation • More than 97% of the samples have error < 10% • If we consider median over 10 consecutive samples, 99.3% of the samples have error < 10%

  38. NEWS: Loss-Rate Estimation • Accuracy of 90% in over 80% of the cases that have loss rate more than 0.1% • Performs well in identifying high lossy links

  39. NEWS: Avail-BW Estimation • Relative error < 0.5 in 60% of the cases • Underestimates for Far-Far • Overestimates for Far-Close in some cases • Compare with stable TCP bandwidth • Measurement points are classified on the basis of distance of two targets from the source of measurement

  40. Scalability • Delay based route selection • 90th percentile RDP is 2.33 (HRG), 3.74 (RG) and 1.16 (PRG) RG = Random gh PRG = Proximity random gh HRG = Hierarchical random gh Transit stub network 16384 nodes Average node degree = 20

More Related