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#Qtox connection problems how to

Figure 4 shows a basic connectivity check.

The result of both agents testing is a 4-way handshake on the exact same ports that will be used for media. Figure 3 shows the components of the candidate pairs that make up the UA check list. Each UA gathers these into check lists and schedules connectivity checks, STUN request/response transaction, to see which pairs work. Each UA takes the two lists of candidates and pairs them up to make candidate pairs. UA2 performs the same candidate gathering and sends a SDP response with it’s list of candidates.

Server Reflexive Candidate – translated address on the public side of the NAT (obtained from either a STUN server or a TURN server)įigure 2 shows the relationship of these candidates to the UA.Īfter UA1 has gathered all of its candidates, it arranges them in order of priority from highest to lowest and sends them to UA2 in attributes in an SDP offer message.

Relayed Candidate – transport address associated with a TURN server (can only be obtained from a TURN server).

Host Candidate – transport address associated with a UA’s local interface.

Transport addresses are a combination of IP address and port for a particular transport protocol. To execute ICE UAs have to identify all address candidates, transport addresses. ICE is used to discover which addresses can connect to each other and the method used to make that connection through the NAT. Both UAs have a list of transport addresses that can be used to communicate with another agent. In addition ICE uses STUN/TURN server(s), each UA can have it’s own or they can use the same one. They are capable of exchanging SDP messages through an offer/answer exchange used to setup media sessions between the UAs through a SIP server. The two UAs are each behind a NAT with unknown properties. ICE allows UAs, who are initially ignorant of their topologies, to discover enough topology information to find communications paths.

ICE use SIP, which means that the NAT traversal of SIP must be provided by another mechanism. Both of these IP addresses are meaningless outside the scope of each individual’s private local network and neither party will receive the other’s RTP packets.įigure 1 shows a typical ICE deployment with two User Agents (UAs) communicating via SIP (or other signaling protocol that performs an offer/answer exchange of SDP messages). Bob accepts Alice’s invite with his SDP containing his local IP address 192.168.0.10 and media port 1234. Alice calls Bob and Alice’s invite contains Session Description Protocol (SDP) with her local IP address 10.1.1.10 and media port 1234.

#Qtox connection problems how to

This private IP address is meaningless to a device on the public Internet and the registrar would not know how to reach Bob.Ī second example involves problems in sending Real-time Transport Protocol ( RTP) media. This tells the registrar that Bob can be reached at the IP address 192.168.0.10 at port 5060 (the default SIP port). The SIP device registers its location with the registrar as sip: :5060. The SIP device has a non-routable Private IP address 192.168.0.10. The presence of a Network Address Translator (NAT) presents problems for Voice over IP (VoIP) and WebRTC implementations.Ĭonsider the example using the Session Initiation Protocol ( SIP) where a SIP device with user Bob sits behind a NAT/Firewall and wants to register its location with a SIP registrar located on the public Internet. ICE uses a combination of methods including Session Traversal Utility for NAT ( STUN) and Traversal Using Relay NAT ( TURN). Interactive Connectivity Establishment (ICE) Protocol is used for NAT transversal.