Discussion On Routing Modes IETF72 P2PSIP WG draft-jiang-p2psip-sep-01

1
Discussion On Routing ModesIETF72 P2PSIP WG
draft-jiang-p2psip-sep-01

• Jiang XingFeng Jiang.x.f_at_huawei.com
• Carlos Macian carlos.macian_at_upf.edu
• Victor Pascual victor.pascual_at_tekelec.com

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Routing Modes

• Symmetric Recursive
• Request and corresponding response follow the
  same path
• Adopted in the current RELOAD draft
• Direct Response
• Send response directly back if the requesting
  peer allows it (e.g. it is publicly reachable)
• Relay Peer
• With help from relay peers with unrestricted
  connections, the response could go through the
  relay peer to reach the request originator
• Forward Response
• Response is considered as a distinct transaction
  from request and routed through the overlay based
  on the Node ID of request originator, (i.e.
  routing based on the underlying P2P algorithm)
• Iterative
• where the intermediate peers merely return a
  response indicating the next hop, but do not
  actually forward the message to that next hop
  themselves

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Why Relay Peer And Direct Response? Improve
Success Rate

• NOT meant to REPLACE symmetric recursive
• Enhancement to symmetric recursive
• Could work together with symmetric recursive
• Main Benefit
• Reduce the number of hops of response path to
• Number of hops 1 - Direct Response
• Number of hops 2 - Relay Peer
• Improve success rate of P2PSIP transaction

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Where Is Relay/Direct Response Helpful? Dynamic
Scenarios

• Concerns about routing in P2P systems
• Nodes stability
• Connectivity stability between peers
• Where Symmetric MAY NOT Work Well
• Heavy churn
• Path with larger hop count
• The number of hops often follows a uniform
  distribution within 0, M M lookup complexity
  of the specific algorithm in use
• Symmetric works well with smaller hop count
• Stability of TURN peers has an impact on the
  connectivity stability between peers
• Overlays with large scales, for example, over
  1000 peers

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How Relay Peer Works - 1
X
Request Originator
A
Intermediate Peer
Y
Destination Peer
1
5
Relay Peer
8
5
B
Request
Z
Symmetric Recursive
5
D
4
7
2
Relay Peer
6
C
3
Pre-established connection
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How Relay Peer Works - 2

• A typical message sequence
• Originator discovers relay peers first
• Originator carries info about relay peers in the
  request to be routed around the overlay
• Destination peer sends the responses to the relay
  peers which forwards the response toward the
  request originator
• When Relay Peer is triggered
• The destination peer decides whether or not Relay
  Peer is used
• Possible criteria
• The request has traversed so many hops that it is
  highly probable that one of reverse connections
  broke down

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Concerns Relay Peer

• Relay Peer
• Considered as a kind of service, just like
  STUN/TURN service
• Unrestricted connection Identify Relay Peer
• Possible to decide whether a peer is on the
  public Internet in P2PSIP, for example, with the
  help from bootstrap peer or enrollment server who
  are already on public Internet
• While being on the public Internet, a peer can
  use Direct Response to determine whether or not
  it is behind a firewall or address-independent
  firewall

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Concerns DoS Attack

• Attack 1
• A large number of responses are sent to the Relay
  peer to overload the Relay peer
• Relay peer only forwards response to the peer
  with whom (peer) it has direct connections
• Attack 2
• Malicious peers send a great number of requests
  and the destination peer may try using Relay Peer
  and symmetric recursive routing at the same time,
  which will amplify the number of the response to
  the request originator
• Destination peer will base response on some
  criteria treated as a parameter, such as total
  hops the requests traversed, to decide whether
  relay peers are used to route the response
• This mitigates the impact from the response
  amplification

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Next Step

• Adopted as a WG item (Direct Response and Relay
  Peer)?
• Or
• The choice of Routing modes be a open issue and
  need more investigation? (including symmetric
  recursive)