Atomized Routing Analysis

1
Atomized Routing Analysis

• Duc Ngo (gte774t_at_mail.gatech.edu)
• Chau Vo (gt7923c_at_mail.gatech.edu)
• Ziru Zhu (ziru_at_cc.gatech.edu)

2
Agenda

• Introduction Background
• Related Works
• Atomized Routing
• Project Status
• QA

3
Introduction

• Autonomous System (AS)
• Single common administration
• Border Gateway Protocol (BGP)
• Backbone protocol of the Internet
• Inter-domain (AS) routing protocol
• Reachability information exchanged between
  adjacent BGP routers over TCP
• BGP Terminology
• ASPATH the advertisement path along
• which the update messages traverse
• Default-Free Zone (DFZ) consists of routers
• in which do not contain a default entry in the
• routing table

4
BGP Policy Routing

• BGP provides capability for enforcing various
  policies
• Policies are not part of BGP they are provided
  to BGP as configuration information
• BGP enforces policies by
• choosing paths from multiple alternatives, and
• controlling advertisement to other ASs

5
Policy Example

• Types of AS
• Stub
• Multi-homed
• Transit
• A multi-homed AS refuses to act as a transit
• An AS can favor or disfavor certain ASs for
  traffic transit from itself

6
BGP Policy Routing - Problems

• Rapid growth of BGP routing tables
• Overload of route update traffic
• Cumbersome policy configuration
• Complicated by engineering efforts like
  Multi-homing, NAT, and mobility
• Lacking verification tools prior to load
• No synchronization ability

7
Prefix Clustering

• Routing computations are applied on clustering
  group rather than on each prefix
• Updating to prefixes can be aggregated to one
  update per cluster
• Policy can be applied on cluster basis
• However,

Information reduction may imply a reduction in
granularity of policy control - after information
is collapsed, the same policies will apply to all
destinations and paths in the equivalence class.
RFC 1771
8
Related Works

• Classless Inter-Domain Routing (CIDR)
• Andersons Distance Metric Clustering
• Hustons Atoms
• Kastenholzs Aggregates
• Broido Claffys Atomized Routing

9
Classless Inter-Domain Routing (CIDR)

• Reconstruct IP address space to increase
  assignment efficiency
• Allows prefixes with variable length so address
  assignment can be fit to specific need (prefix
  format, addr/p)
• Support hierarchical route aggregation
• Allows adjacent destination address space
  aggregated into single entry in routing table
• Shrinks the routing table size reduces traffic
  overload

10
CIDR (Cont.)

• CIDR may fail when
• Multi-homing
• announce a global route through several upstream
  providers
• Load balancing of incoming traffic
• Prefixes with different attributes
• Fragmented address space

11
David Andersons Distance Metric Clustering

• Grouping prefixes based on similarities between
  the routes update times
• Capture the update patterns via 0/1 vectors
• Did an update happen in time t, t?t
• Measure the closeness of two update vectors
• Correlation coefficient

12
Distance Metric Clustering (Cont.)
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Distance Metric Clustering (Cont.)

• Learning prefix clusters only based on BGP
  dynamics
• No clear answer to what such clusters reflect in
  the reality
• Topology?
• Prefix assignment?
• ASPATH sharing
• Only useful for analysis

14
Geoff Hustons Atoms

• Group all prefixes within an AS into one big
  routing atom
• Perform topology calculation on atom IDs (AS
  numbers)
• No reduction on the number of routes or prefixes
• Lose some granularity of the possible policy
  control

15
Frank Kastenholzs Aggregates

• Observation
• the topology calculation is the problem
• Separates aggregate IDs from aggregate contents
• Known only by routers
• Used only for topology calculations
• To get to Aggregate A the next hop is router R
• Internal structure hidden Support
  sub-aggregation
• Not addressing
• How to form such aggregation?
• How to apply policies over the aggregates?

16
Atomized Routing

• Another form of Prefix Clustering
• Will be covered in detail by Duc

17
Policy Atoms

• First introduced by Broido and Claffy
• Two types
• Computed Atom
• Declared Atom

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Computed Atoms

• Prefixes that share the same set of AS PATHs
• Derived from the global picture of the routing
  system
• Observed or computed from the whole routing system

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Computed Atoms (cont.)
AS80 Prefix 3.0.0.0/8 ASPath 13129 1239
80 ASPath 7018 80 ASPath 9999 1239 80
Atom 1 Prefix 4.0.0.0/8 ASPath 13129
1239 80 ASPath 3549 1239 80 ASPath 7018
80 Atom 2 Prefix 5.0.0.0/8 ASPath
7018 80 Atom 3 Prefix 6.0.0.0/8
ASPath 13129 1239 80 ASPath 3549 1239 80
ASPath 7018 80 Atom 2
AS100
AS80
3.0.0.8/8
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Computed Atoms (cont.)
AS80 Prefix 3.0.0.0/8 ASPath 13129 1239
80 ASPath 7018 80 ASPath 9999 1239 80
Atom 1 Prefix 4.0.0.0/8 ASPath 13129
1239 80 ASPath 3549 1239 80 ASPath 7018
80 Atom 2 Prefix 5.0.0.0/8 ASPath
7018 80 Atom 3 Prefix 6.0.0.0/8
ASPath 13129 1239 80 ASPath 3549 1239 80
ASPath 7018 80 Atom 2
AS100
4.0.0.8/8
AS80
3.0.0.8/8
21
Computed Atoms (cont.)
AS80 Prefix 3.0.0.0/8 ASPath 13129 1239
80 ASPath 7018 80 ASPath 9999 1239 80
Atom 1 Prefix 4.0.0.0/8 ASPath 13129
1239 80 ASPath 3549 1239 80 ASPath 7018
80 Atom 2 Prefix 5.0.0.0/8 ASPath
7018 80 Atom 3 Prefix 6.0.0.0/8
ASPath 13129 1239 80 ASPath 3549 1239 80
ASPath 7018 80 Atom 2
AS100
4.0.0.8/8
6.0.0.8/8
AS80
3.0.0.8/8
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Computed Atoms (cont.)
AS80 Prefix 3.0.0.0/8 ASPath 13129 1239
80 ASPath 7018 80 ASPath 9999 1239 80
Atom 1 Prefix 4.0.0.0/8 ASPath 13129
1239 80 ASPath 3549 1239 80 ASPath 7018
80 Atom 2 Prefix 5.0.0.0/8 ASPath
7018 80 Atom 3 Prefix 6.0.0.0/8
ASPath 13129 1239 80 ASPath 3549 1239 80
ASPath 7018 80 Atom 2
AS100
4.0.0.8/8
6.0.0.8/8
AS80
5.0.0.8/8
3.0.0.8/8
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Declared Atoms

• Prefixes that share the same set of origin links
• e.g
• Derived from the local view of the Internet
• Declared by the origin AS

AS1
AS2
AS3
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Declared Atoms (cont.)
AS80 Prefix 3.0.0.0/8 OriginLinkSet 1239
80 OriginLinkSet 7018 80 Atom 1
Prefix 4.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1 Prefix
5.0.0.0/8 OriginLinkSet 7018 80 Atom 2
Prefix 6.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1
AS13129
AS7018
3.0.0.8/8
AS80
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Declared Atoms (cont.)
AS80 Prefix 3.0.0.0/8 OriginLinkSet 1239
80 OriginLinkSet 7018 80 Atom 1
Prefix 4.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1 Prefix
5.0.0.0/8 OriginLinkSet 7018 80 Atom 2
Prefix 6.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1
AS13129
AS7018
4.0.0.8/8
3.0.0.8/8
AS80
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Declared Atoms (cont.)
AS80 Prefix 3.0.0.0/8 OriginLinkSet 1239
80 OriginLinkSet 7018 80 Atom 1
Prefix 4.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1 Prefix
5.0.0.0/8 OriginLinkSet 7018 80 Atom 2
Prefix 6.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1
AS13129
AS7018
4.0.0.8/8
5.0.0.8/8
3.0.0.8/8
AS80
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Declared Atoms (cont.)
AS80 Prefix 3.0.0.0/8 OriginLinkSet 1239
80 OriginLinkSet 7018 80 Atom 1
Prefix 4.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1 Prefix
5.0.0.0/8 OriginLinkSet 7018 80 Atom 2
Prefix 6.0.0.0/8 OriginLinkSet 1239 80
OriginLinkSet 7018 80 Atom 1
AS13129
AS7018
4.0.0.8/8
5.0.0.8/8
3.0.0.8/8
AS80
6.0.0.8/8
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Atomized Routing Architecture

• Four major parts
• Atom computation
• Updates to routes of atoms
• Packet forwarding
• Membership protocol

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Atomized Routing Architecture

• Four major parts
• Atom computation
• Updates to routes of atoms
• Packet forwarding
• Membership protocol

30
Atomized Routing Architecture

• Four major parts
• Atom computation
• Updates to routes of atoms
• Packet forwarding
• Membership protocol

31
Atomized Routing Architecture

• Four major parts
• Atom computation
• Updates to routes of atoms
• Packet forwarding
• Membership protocol

ER
ER
Source
Destination
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Atomized Routing Architecture

• Four major parts
• Atom computation
• Updates to routes of atoms
• Packet forwarding
• Membership protocol

33
Atomized Routing Benefits

• Routing computations are performed per atom
  instead of per prefix
• Shrink the size of routing table
• Hide the route updates to prefixes
• Reduce the update traffic load

34
Project Status

• Goal
• Analyze the atomized routing architecture
• Compare the effectiveness of the two types of
  atoms
• Study how the BGP policy atoms can help to reduce
  the complexity of global routing policies
• Explore other alternatives

35
Current Implementation

• Download BGP routing table and update messages
  from RIPE
• Parse the BGP table
• Calculate the policy atoms based on their
  definitions

36
Next Steps

• Estimate number of policy atoms per AS
• Analyze the stability of policy atoms
• Analyze the reduction gains when prefixes are
  replaced with policy atoms
• Analyze the ratio of the number of routes
  covering complete atoms to the number of all
  routes within the same update message

37
Question?