The RFC states that the browser has to assign a priority to ICE candidates. In my understanding, an ICE candidate may encompass a TURN server to use.
How the browser assigns this priority is left to the implementation. We would like to implement our own protocol.
If we can calculate such a priority, how can we influence the browser to use our priority when sending ICE candidates?
The priority of the TURN server is determined by the priority of the ICE candidate. That's right! And, as I googled, the text/document summarized for the priority of the ICE candidate was in Stack Overflow. Please read it once and refer to it:
How does WebRTC decide which TURN Servers to Use
Thank you.
Related
it might seem like this question can be easily found in google, however all I can see are theoretical answers and not practical ones.
When an SDP offer or answer is created, my clients start releasing ICE Candidates, which I save into an array and send to the other client I want to connect with, and vise versa.
Now, both clients have access to their own ICE Candidates, and the ICE Candidates of the client they want to connect with. But how do I choose the best one, and if not so, how can I try all of them and see which one works?
Thank you.
You shouldn't keep ICE candidates in array, but send each candidate immediately. WebRTC has own logic to select the best pair of candidates depending on various factors, like network cost (for example, WiFi candidate is more preferable than LTE).
I am implementing a TURN server specifically for WebRTC usage and have some questions regarding not supporting certain attributes (send an error response if the attribute is received) or simply ignore them or other doubts. Here they are:
EVEN-PORT If my SDP always signals a=rtcp-mux, will this attribute ever be used? And if so, would it be an error if it appears?
RESERVATION-TOKEN Does this play any role when TURN server is used in the WebRTC context?
SOFTWARE As in STUN, can this be safely ignored without any processing?
DONT-FRAGMENT Is there a preferred and well-accepted norm for this attribute in the WebRTC context?
What is the ideal length of NONCE in the WebRTC context?
Different issue. Are there any statistics available for use of TURN server for transports other than UDP? I am thinking of supporting only UDP for now.
webrtc typically requires rtcp-mux, at least in chrome so I would not care about even-port.
no
yes. It is FYI only.
no. WebRTC implementations typically don't do path-mtu discovery but assume 1200 bytes.
You mean the expiration? https://medium.com/confrere/gone-in-1100-seconds-hunting-bugs-on-the-edge-of-webrtc-132a186c45dd
see https://medium.com/the-making-of-whereby/what-kind-of-turn-server-is-being-used-d67dbfc2ff5d
In a Webrtc call, I am using sip signalling and sdp for media parameter negotiation.
Before call start, I do a stun-bind transaction and get reflexive candidates. I have put those reflexive candidates in sdp in addition to base and host candidates.
As soon as we get 200 OK for Invite, we need to start media. For media start, I need to know which candidate pair I need to use.
I hope to determine which candidate pair I need to use, we need to do connectivity check. I am not sure how to do connectivity check (like which message to send.. etc).
Can somebody help me in this to understand.
Also is there an open source (c, linux based), that gives ice/stun/turn support.
This information is given on RFC 5245. You need to read this RFC for implementing ICE. For your query about doing ICE connectivity check, read this section of the RFC.
Also is there an open source (c, linux based), that gives
ice/stun/turn support.
Search google for this and you will get your answer.
Related WebRTC, ICE protocol gives the which pair of addresses will work for direct media transfer between the pairs.
Let A and B are two endpoints
To choose which address will work for direct communication between A and B, Person A first gather candidates, encode candidate attribute, encode the SDP offer message, and send it to another endpoint.
When B get offer message from A,then person B gather candidates, encode the SDP answer message with its own list of candidates and send it to person A.
At this end of this process, each agent has a complete list of local candidates and Remote candidates. Its pairs them up, resulting in CANDIDATE PAIRS. To see, which pair work, each agent performs the connectivity checks using STUN req/resp.
How many connectivity checks are performed, to nominate valid candidate pair?
What are the remaining ICE connectivity checks are performed regarding webRTC call?
To develop ICE module for webRTC call, I have to follow each step in RFC5245 or any thing else?
How many connectivity checks are performed, to nominate valid
candidate pair?
The number of candidate pairs are the number of connectivity checks done by each side.
What are the remaining ICE connectivity checks are performed regarding
webRTC call?
There are no extra ICE connectivity checks for webRTC.
To develop ICE module for webRTC call, I have to follow each step in
RFC5245 or any thing else?
You have to implement or use existing implementation of DTLS protocol, RFC5763 and RFC5764. DTLS implementation can be found on OpenSSL library.
All these seems a lot of work but if you use openssl then its easy enough.
I newly wrote a simple chat application, but I didn't really understand the background of ICE Candidates.
When the peer create a connection they get ICE Candidates and they exchange them and set
them finally to the peerconnection.
So my question is, where do the ICE Candidates come from and how are they used and are they all really used ?
I have noticed that my colleague got less candidates when he executes the application on his machine, what could be the reason for different amount of Candidates ?
the answer from #Ichigo is correct, but it is a litte bit bigger. Every ICE contains 'a node' of your network, until it has reached the outside. By this you send these ICE's to the other peer, so they know through what connection points they can reach you.
See it as a large building: one is in the building, and needs to tell the other (who is not familiar) how to walk through it. Same here, if I have a lot of network devices, the incoming connection somehow needs to find the right way to my computer.
By providing all nodes, the RTC connection finds the shortest route itself. So when you would connect to the computer next to you, which is connected to the same router/switch/whatever, it uses all ICE's and determine the shortest, and that is directly through that point. That your collegue got less ICE candidates has to do with the ammount of devices it has to go through.
Please note that every network adapter inside your computer which has an IP adress (I have a vEthernet switch from hyper-v) it also creates an ICE for it.
ICE stands for Interactive Connectivity Establishment , its a techniques used in NAT( network address translator ) for establishing communication for VOIP, peer-peer, instant-messaging, and other kind of interactive media.
Typically ice candidate provides the information about the ipaddress and port from where the data is going to be exchanged.
It's format is something like follows
a=candidate:1 1 UDP 2130706431 192.168.1.102 1816 typ host
here UDP specifies the protocol to be used, the typ host specifies which type of ice candidates it is, host means the candidates is generated within the firewall.
If you use wireshark to monitor the traffic then you can see the ports that are used for data transfer are same as the one present in ice-candidates.
Another type is relay , which denotes this candidates can be used when communication is to be done outside the firewall.
It may contain more information depending on browser you are using.
Many time i have seen 8-12 ice-candidates are generated by browser.
Ichigo has a good answer, but doesn't emphasise how each candidate is used. I think MarijnS95's answer is plain wrong:
Every ICE contains 'a node' of your network, until it has reached the outside
By providing all nodes, the RTC connection finds the shortest route itself.
First, he means ICE candidate, but that part is fine. Maybe I'm misinterpreting him, but by saying 'until it has reached the outside', he makes it seem like a client (the initiating peer) is the inner most layer of an onion, and suggests the ICE candidate helps you peel the layers until you get to the 'internet', where can get to the responding peer, perhaps peeling another onion to get to it. This is just not true. If an initiating peer fails to reach a responding peer through the transport address, it discards this candidate and will try a different candidate. It does not store any nodes anywhere in the candidate. The ICE candidates are generated before any communication with the responding peer. An ice candidate does not help you peel the proverbial NAT onion. Also regarding the second quote I made from his answer, he makes it seem like ICE is used in a shortest path algorithm, where 'shortest' does not show up in the ICE RFC at all.
From RFC8445 terminology list:
ICE allows the agents to discover enough information
about their topologies to potentially find one or more paths by which
they can establish a data session.
The purpose of ICE is to discover which pairs of addresses will work. The way that ICE does this is to systematically try all possible pairs (in a carefully sorted order) until it finds one or more that work.
Candidate, Candidate Information: A transport address that is a
potential point of contact for receipt of data. Candidates also
have properties -- their type (server reflexive, relayed, or
host), priority, foundation, and base.
Transport Address: The combination of an IP address and the
transport protocol (such as UDP or TCP) port.
So there you have it, (ICE) Candidate was defined (an IP address and port that could potentially be an address that receives data, which might not work), and the selection process was explained (the first transport address pair that works). Note, it is not a list of nodes or onion peels.
Different users may have different ice candidates because of the process of "gathering candidates". There are different types of candidates, and some are obtained from the local interface. If you have an extra virtual interface on your device, then an extra ICE will be generated (I did not test this!). If you want to know how ICE candidates are 'gathered', read the 2.1. Gathering Candidates