Topology Discovery Research

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Topology Discovery Research

• Suman Pandey

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Discovering Internet Topology

• R. Siamwalla, R. Sharma, and S. Keshav
• Cornell Network Research Group
• Department of Computer Science
• Cornell University, Ithaca, NY 14853
• rachit, sharma, skeshav_at_cs.cornell.edu ,IEEE
  INFOCOM 1999

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Discovering Internet Topology

• Ping/Broadcast Ping
• Traceroute
• Zone transfer from DSN server
• SNMP
• Subnet Guessing Algorithm

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Discovering Internet Topology
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Topology Discovery in Heterogeneous IP
NetworksThe NetInventory System

• Yuri Breitbart, Minos Garofalakis, Member, IEEE,
  Ben Jai, Cliff Martin, Rajeev Rastogi, and
• Avi Silberschatz,
• IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 12, NO.
  3, JUNE 2004 401

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General Ideas (NetInventory)

• Discover layer 2 and layer 3 devices
• Target multi vender ip networks. Relies on AFT
  Aij of each interface of the node ( in absence of
  AFT it used NetToMedia Table)
• AFT is made based on the Backward learning.

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AFT (NetInventory)

• This is the table associated to a port the MAC
  address of the hosts that can be reached through
  that port Aij
• Aij corresponds to the set of nodes in N that are
  reachable from Si via the interface Sij by a path
  in the switched domain spanning tree.
• This is calculated by using backward learning
• The AFT should be complete. For AFT to be
  complete there can be two approach used
• Generate extra traffic between nodes by sending
  icmp (echo request )
• Write a data collection program which can copy
  the AFT at regular intervals and does not age out
  the table entries as switch does.

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Basic formulas for connectivity (NetInventory)

• Switch to switch connectivity
• µ is set of MAC address corresponding to the
  switches and routers of subnet S.
• Interfaces Sij and Skl are directly connected to
  each other if and only if Aij U Akl µ and Aij n
  Akl F .
• There can not be a loop in the AFT because it is
  based on the spanning tree protocol.
• Switch to Router connectivity
• If for an interface of a switch Si there doest
  exist any other interface of any other switch
  then that becomes the leave interface.
• A router R is connected to an interface if and
  only if Sij is a leaf interface and Aij contains
  the MAC address of R

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Problem with Multiple Subnet (NetInventory)
A12 S4 A21 S1 A22 S3,S4 A31
S2,S1 A32 S4 A41 S1

• A switch may not always see adjacent switches
  belonging to a different subnet
• S1 does not see S2 and S3
• From previous lemma, one cannot deduce that S12
  and S21 are connected
• The union of A12 and A21 is not equal to the
  set of all MAC addresses
• A12 A32 and A21 A41

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Problem with Multiple Subnet (NetInventory)
A12 S4 A21 S1 A22 S4 A31 S1 A32
S4 A41 S1
S1
R1
S1
R1
S12
S12
4
4
S21
S31
1
1
S2
R2
S3
R3
S22
S32
4
4
S31
S21
1

• Impossible to distinguish between topologies 1
  and 2 based only on AFTs

1
R3
R2
S3
S2
S32
S22
4
4
S41
S41
1
1
S4
S4
Topology 1
Topology 2
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Formulas for Switched Domain on Multiple Subnet
(NetInventory)

• Ex So in this network S1, S4 and router R1
  belong to subnet 1 and S2, S3 and Router R2
  belong to subnet 2.
• valid Unions
• U1221 U3241 S1, S4, R1
• U2231 S1, S2, S3, S4, R1, R2
• Invalid Unions
• U1231 S1, S2, S4, R1, R2 , This is invalid
  according to rule 2, because it contains switch
  S2 but not S3 containing to the same subnet.
• U1241 S1, S4, R1 This is invalid
  according to rule 3 . As U1241 U1221 and
  switches S1 and S4 belong to same subnet. While
  S1 and S2 belong to different subnet.
• Conclusion
• S12 is connected to S21
• S22 is connected to S31
• S32 is connected to S41
• So the network shown in the above will be
  converted to the network shown in the picture
  below

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Results of NetInventory
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Results of NetInventory

• Dealing with completeness Requirement of AFT and
  the Heuristics.
• How to collect AFT of different vendors, is not
  explained
• They talk about heterogeneous implementation, and
  handling of Interfaces, fast Ethernet, ATM, FDDI,
  SONET and Frame Relay interface, but there are no
  explanation

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Topology Discovery for Large Ethernet Networks

• Bruce Lowekamp, David R. OHallaron, Thomas R.
  Gross , CMU

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CMU

• Proof by Contradiction
• Through sets
• The through sets contain the addresses that are
  forwarded through each port in other words, the
  addresses that are on other ports, for which the
  bridge will forward packets through itself. The
  through sets for each port are, in a sense, the
  complement of Fxi (Aij) and are denoted Txi
  (Tij),

NetInventry formula
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CMU

• Basic theorems
• Let a,b N. Suppose there exists exactly one
  pair of ports x and y such that Txa n Tyb F.
  Then ax and by are connected. Furthermore, if ax
  and by are connected, then Txa n Tyb F.

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CMU Formulas for connectivity

• Each bridge has an entry for the others address
  in its FDB, not including out-of-band ports or
  This condition is satisfied in the entire AFT
  table we have above.
• Bridge a has an entry for b in Fxa and ?k ! x
  Fyb n Fka ! F
• Forwarding entries for three nodes are shared
  between a and b, divided among at least two ports
  on one of a or b and three ports on the other
  bridge. x and y must be included in those ports.
  Formally, ?i, j, i ! j (Fxa n Fib ! F ? Fxa
  n Fjb ! F ), and ?k ! x Fyb n Fka ! F.

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Constella A Complete IP Network Topology
DiscoverySolution

• Fawad Nazir1,2,4, Tallat Hussain Tarar3,4, Faran
  Javed4, Hiroki Suguri5, Hafiz Farooq Ahmad4,5,
  Arshad Ali4
• 2007

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Constella Design
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Thank You ?