Determining Grid machine and Network Topology

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Determining Grid machine and Network Topology

• -By Tarun Saxena

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Why, What for and when

• To be used initially before setting up of the
  grid to discover undocumented hosts on the
  network.
• Determining the route lengths between potential
  Grid resources. To optimize Grid structure.
• To assist in preventing collisions during the
  operation of bandwidth estimation algorithms.

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Goal of the project

• Complete and accurate discovery of hosts and
  distances within the local network .

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Scope and future extensions

• We will focus on discovery on interconnections on
  layer 3 i.e. the network layer. More specifically
  the IP protocol only. Ignoring the finer
  interconnections using switches etc.
• In future we may add extensions to support
  discovery at lower levels and add bandwidth
  estimation also. Support for other layer 3
  protocols like IPX can be added.

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Methods / tools for discovery

• SNMP
• Traceroute
• Ping
• DNS
• Proprietary protocols like NetFlow by Cisco
• ARP tables (Ethernet) and sniffing

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SNMP

• Simple Network Management Protocol
• Latest and perhaps the most powerful of all
  methods.
• Gather information from the MIB (Management
  Information Base) of every host.

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Traceroute

• Discover intermediate nodes to a known host,
  using short lived packets.
• These intermediate routers can be queried using
  SNMP or protocols used for router information
  transfer.
• Corresponding to their addresses their local
  networks could be guessed.
• These guessed hosts could be pinged and
  tracerouted.

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Ping

• Basic method to check if a host is reachable.
• Broadcast pings can be used to discover all hosts
  in a sub network. Can be used to guess and verify
  the subnet mask.

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Proprietary Protocols

• Routers exchange information using certain
  protocols. Like Cisco routers communicate using
  Netflow.
• The discovery system can act as a router and read
  information about the hosts servable by known
  routers.

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DNS

• Domain Name Server
• Zone transfer facility can be used to discover
  all hosts in a subnetwork.
• Ex. A zone transfer on iisc.ernet.in will give
  all sub-domains like serc.iisc.ernet.in etc.
• Reverse Name query on an IP can give domain name
  which can be used to guess other domain names.

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Approach

• Start with broadcast ping on local network.
• Get as much info as possible from the local
  router using SNMP and any proprietary protocols
  if available.
• Reverse DNS on known hosts and then zone transfer
  on the names. Ex. Reverse DNS on 144.16.79.50
  will give serc.iisc.ernet.in. Now try DNS on
  iisc.ernet.in and then on ernet.in and so on.
• Broadcast ping in subnets of each of the newly
  discovered hosts.

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Approach (contd)

• For larger radius of discovery try tracerouting
  to some known site like www.google.com.
• Broadcast in the guessed local networks of each
  of the discovered routers.
• Use other heuristics, like setting up a Grid in
  IISc would require discovery of hosts under
  144.16.x.y.

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References

• www.cc.gatech.edu/people/home/gantsich/Projects/CS
  7001_Project1/Report.html
• Discovering Internet Topology R.Siamwalla, R.
  Sharma and S.Keshav
• www.cs.cornell.edu/boom/1999sp/projects/Network20
  Topology/topology.html
• SNMP RFC 1157