Jack Chang, chief operating officer of SIP-based global Internet telephony service TelTel, takes on several issues and obstacles often associated with SIP P2P. These include Scaling and Reliability challenges, Denial of Service concerns, authentication, and NAT/Firewall traversal.
The last section is especially interesting. Chang describes some of the bandwidth limitations of Session Border Controllers, and comes down on the side of Interactive Connectivity Establishment, or ICE.
"The ICE algorithm uses existing protocols, Simple Traversal of UDP Through NAT (STUN) and Traversal Using Relay NAT (TURN), to discover and create mutual media connections," Chang writes. "Although this is a relatively new proposal, this methodology will allow clients to decide on the best connection for the media session."
Chang adds another argument for ICE. "It will create the session only if the media will work ensuring that successful signaling corresponds to a working media connection," he writes. "Deploying ICE will push the intelligence of determining the media pathway out to edge and make the deployment more inline to a peer-to-peer service."