HLP: A Next Generation Interdomain Routing Protocol

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HLP A Next Generation Interdomain Routing
Protocol

• Lakshminarayanan Subramanian,
• Matthew Caesar, Cheng Tien Ee,
• Mark Handley, Morley Mao,
• Scott Shenker, Ion Stoica
• To be appeared in SIGCOMM 05

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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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Introduction

• BGP4 is the only inter-domain routing protocol in
  use.
• Inter-domain routing protocol should satisfy
  basic properties, such as scalability, robustness
  ,rapid convergence and policy routing.
• This paper describes a hybrid link-state and path
  vector protocol (HLP).

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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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Background

• (BGP recap)
• Path vector protocol
• Incremental Updates
• Policy Enforcement
• Classless Inter-Domain Routing

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Background

• (BGP Problems)
• Route flapping -It is a propagation problem.
• Security-BGP does not prevent an AS from
  advertising arbitrary prefixes
• Peer scaling - Each must have a peer connection
  to every other router creating a scaling
  problem as the number of connections increases
  exponentially with each new router added.

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Background (Cont.)

• BGP does not distribute policy information.
• HLP expose the common case of policies.
• Common and inferable relationship Provider and
  customer relationship.
• HLP leverages the common case policy behavior
  that BGP cannot hide and optimizes the protocol
  design.

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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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Design Philosophy

• Scalability
• 3000 ASs and 17,000 prefixes in 1997
• More than 50,000 ASs and 180,000 prefixes now
• Convergence and Route Stability
• Isolation Isolate local faults within a network.
• HLP Hide unnecessary routing updates across
  provider-customer hierarchies.
• HLP does not use BGPs prefix-deaggregation to do
  traffic engineering.

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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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Distinction between BGP and HLP
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Distinction between BGP and HLP (Cont.)

• Routing structure - HLP avoids error propagation
  by hiding some path information using
  hierarchical routing structures.
• Policy - 99 of the ASs follow two simple
  guidelines.
• Export-rule guideline Do not forward route
  advertised by one peer or a provider to another
  peer or another peer or provider.
• Route preference guideline Prefer
  customer-routes advertised by peers or providers.

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Distinction between BGP and HLP (Cont.)

• Routing Granularity - Number of distinct paths
  from a vantage point to destination is less than
  2 for more than 99.
• Routing Style-
• PV- Worst case convergence grows exponentially
  with the length of the path
• LS- Violates privacy of policies by revealing
  every activity to all destinations.
• HLP uses LS within a given hierarchy and uses PV
  across hierarchies.

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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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HLP Routing Model
Assumption No cycles in Provider-Customer
relationship
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HLP Routing Model
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HLP Routing Model (Cont.)

• (Summary)
• All ASs maintain a link-state database in their
  local hierarchy.
• FPV includes peering links but excludes the parts
  within the hierarchies.
• Cost metrics are added to the cost value in an
  FPV advertisement.

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HLP Routing Model (Cont.)
Explicit Information Hiding
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HLP Protocol Model
Prefix-level route selection. BGP uses
prefix-deaggregate for traffic engineering. HLP
uses information hiding.
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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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HLP Protocol Analysis

• (Quantification)
• Isolation-The number of ASs that can potentially
  be affected by a routing events.
• Churn-The total number of updates generated by an
  event.
• Topology 16774 ASs and 37066 inter-AS links.

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HLP Protocol Analysis
Churn reduction in HLP is due to a) using the
AS-prefix mapping b) cost hiding of route
updates.
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HLP Protocol Analysis
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HLP Protocol Analysis
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HLP Protocol Analysis
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HLP Protocol Analysis
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Roadmap

• Introduction
• Background
• Design Philosophy
• Distinctions between BGP and HLP
• HLP Routing Model
• HLP Protocol Analysis
• Conclusion

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Conclusion

• HLP performs better than BGP in isolation and
  churn reduction.
• HLP converges faster and it provides a better
  security than BGP .
• We shall wait and see whether BGP will be
  replaced or not since old habits are hard to die.