Routing as a Service

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Routing as a Service

• Karthik Lakshminarayanan
• (with Ion Stoica and Scott Shenker)
• Sahara/i3 retreat, January 2004

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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!

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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

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Routing in transportation network
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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

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System architecture

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

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System architecture

• 2. NEWS/Route selector
• Aggregates network information
• Selects routes on behalf of applications

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System architecture

• 3. End-hosts
• Queries NEWS to setup paths

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Architectural position
Infrastructure
Host
Data plane
Internet Infrastructure overlays
Control plane
P2P End-host overlays
Data plane
Control plane
Our proposal
Data plane
Control plane

• Separate control plane and data plane by using
  clean abstractions

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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

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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

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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

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1. Trust

• NEWS provides routes across the network

• Verification Network verifies correctness

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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

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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

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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

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Summary of results

• Verification of measurement techniques
• Delay 97 of cases have error lt 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

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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

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Backup slides
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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)
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NEWS Measuring loss rate
n2
n1

• Forwarding links
• (n11? n21)
• (n11 ? R)
• (n21 ? n12)
• (n21 ? R)
• (n12 ? R)

R
To measure loss(n1?n2)
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NEWS Measuring loss rate
n1
n2

• Forwarding links
• (n11? n21)
• (n11 ? R)
• (n21 ? n12)
• (n21 ? R)
• (n12 ? R)

To measure loss(n1?n2)
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NEWS Measuring loss rate
n2
n1

• m2 used to differentiate loss on (n1?n2) from
  that on (n2?n1)
• (m ? m1 ? m2) ? loss on virtual link (n1?n2)
• False positives
• False negatives
• Probability of false positives/negatives O(p2 )

R
To measure loss(n1?n2)
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NEWS Available bandwidth
n2
n1

• Delay-based bandwidth measurement (TCP Vegas
  like)
• Increase sending rate till increase in delay is
  seen

cwd1
cwd2
cwd4
R
T received time sent time T smallest RTT
seen thus far
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NEWS Available bandwidth
n2
n1

• Use packet replication to identify if the
  bottleneck is on (n1?n2) or not

cwd2
cwd3
R
T received time sent time
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NEWS Available bandwidth
n2
n1

• Use packet replication to identify if the
  bottleneck is on (n1?n2) or not

cwd2
R
T received time sent time
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NEWS Bottleneck bandwidth
n2
n1
Bottleneck

• Packet-pair-like technique

R
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NEWS Bottleneck bandwidth
n2
n1

• BBW kp/d1, where k deg of replication
• More the degree of replication, greater is the
  possibility of error
• Intervening packets would affect this

Bottleneck
R
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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

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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

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Scalability

• Multiple vantage points for measurements/monitorin
  g
• Maintain a subset of links
• Division of overlay graph to reflect underlying
  paths

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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 vN, each measurement point
  responsible for only O(vN) links

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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

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Evaluation

• Effectiveness of indirect measurements
• Planetlab experiments
• Scalability techniques

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NEWS Delay Estimation

• More than 97 of the samples have error lt 10
• If we consider median over 10 consecutive
  samples, 99.3 of the samples have error lt 10

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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

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NEWS Avail-BW Estimation

• Compare with stable TCP bandwidth
• Measurement points are classified on the basis
  of distance of two targets from the source of
  measurement

• Relative error lt 0.5 in 60 of the cases
• Underestimates for Far-Far
• Overestimates for Far-Close in some cases

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Scalability
RG Random gh PRG Proximity random gh HRG
Hierarchical random gh Transit stub
network 16384 nodes Average node degree 20

• Delay based route selection
• 90th percentile RDP is 2.33 (HRG), 3.74 (RG) and
  1.16 (PRG)