Hi, Another open issue in the “Self-tuning DHT for RELOAD” draft (http://www.ietf.org/id/draft-ietf-p2psip-self-tuning-00.txt) is how to detect peer failure in the case that a peer exits the overlay without sending a Leave message (the leave rate estimation algorithm specified in the draft needs information about detected peer failures and departures in order to work correctly). We can think of at least two alternative ways to detect failed peers:
(1) Use the lack of received STUN keepalives as an indication of peer failure. RELOAD uses STUN for keepalives. STUN keepalives are Binding Indication transactions. Although Binding Indications do not generate a response, the fact that a peer has failed can be learned from the lack of packets (Binding Indications or RELOAD messages) received from the peer. As specified in ICE [1], a peer sends a STUN Binding Indication if there has been no packet sent on a connection for Tr seconds. Our proposal is that if no packets have been received on a connection during the past 2*Tr seconds, a RELOAD Ping request must sent to the remote peer. If the remote peer fails to reply, it will be considered to have failed. (2) Use application-level (i.e., RELOAD) keepalives. If there has been no packet sent on a connection for N seconds (N could be equal to Tr or it could be larger), a RELOAD keepalive message (e.g., Ping) must be sent to the remote peer. The downside of this approach is that the sizes of RELOAD keepalives are much larger than the sizes of STUN Binding Indications. Also, there will be additional ACKs (if the transport is unreliable) sent to acknowledge the reception of RELOAD keepalive requests and responses. Any thoughts on this? Our proposal is to go for alternative (1) since it generates less traffic. Cheers, Jouni [1] Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols draft-ietf-mmusic-ice-19 _______________________________________________ P2PSIP mailing list [email protected] https://www.ietf.org/mailman/listinfo/p2psip
