Internet Topology

1
Internet Topology

• By
• Apan Qasem
• Edwin A. Melendez

2
Overview

• Internet Topology
• Difficulty of Internet Topology Discovery
• Different Algorithms available
• Comparison

3
What is Internet Topology?

• Internet Topology
• A representation of the interconnection between
  directly connected peers on the Internet

4
This is a representation of the EDU Domain
5
Why do we want to know the topology of the
Internet?

• Simulation
• Network Management
• find bottlenecks and failures
• Adding new routers
• Topology-aware algorithms
• improve performance

6
Topology Discovery is a Challenging Task

• Heterogeneous network
• Different hardware and network software
• Different Administration
• Different operational and security policies
• Size of the Internet
• Dynamic nature of the Internet

7
Services Supported by Every Host on the Internet

• Ping
• Demo
• Traceroute
• Demo

8
Current Research

• Information Science Institute at the University
  of South California
• MERCATOR
• Cornell Network Research Group
• Backbone Topology Discovery Algorithm

9
Mercator

• Path Probing
• a modified version of traceroute
• Termination condition
• Hop-limited probes

Source
Destination
10
Mercator

• Source-routed Path Probing
• Directs path probes to discovered routers
• 8 of routers are source-route enabled

Domain A
Probe Source
Domain B
11
Mercator

• Alias Resolution
• Routers may have more than one interface
• Path probes discover router interfaces
• Solution
• Send alias probe to trigger ICMP PORT UNREACHABLE
  which contains source address

A
B
Mercator Host
12
Characteristics of Mercator

• Strengths
• Requires no input
• Can run in any location
• Weaknesses
• All routers are not discovered
• Few details of Sub-networks (e.g. Campus
  networks)
• Slow (few weeks)

13
Cornell Network Research Group Backbone Discovery

• Uses publicly available BGP routing tables
• BGP (Border Gateway Protocol)
• Contains IP addresses of many domains connected
  to the Internet Backbone
• Uses Traceroute to find routers and links

14
Background Topology Discovery

• Get BGP routing info
• Extract domains
• Choose an address
• Foreach address
• Traceroute
• Store all the links and nodes the traceroute
  returns
• Correlate the results

15
Background Topology Discovery

• Strength
• Faster than Mercator (48 hours)
• Weaknesses
• Run from multiple locations to detect cross-links
• Needs input (BGP routing table)

16
Comparison
17
Conclusion

• Internet Topology Discovery is an inherently
  difficult task
• Not enough algorithms
• Currently available algorithms do not produce a
  complete and accurate Internet Map

18
The End