Re: [Serusers] rtpproxy question

I like Maxims idea of inserting a flag in the SDP body most, because it seems to be easy to implement. The drawback is that all SIP providers have to support it - but this problem also occours with the other solutions. regards, klaus > -----Original Message----- > From: Jan Janak [mailto:jan@iptel.org] > Sent: Monday, November 03, 2003 7:11 PM > To: Klaus Darilion > Cc: Maxim Sobolev; serusers(a)lists.iptel.org > Subject: Re: [Serusers] rtpproxy question > > > I think the solution is to modify the RTP proxy. The RTP > proxy should be > symmetric only for user agents that belong to the domain of the proxy > and if the other direction is a foreign user, it should send > the data to > the IP taken from SDP and not wait for any incomming packets. > > Let's take iptel.org as a hypothetical example: > > If both caller and callee have iptel.org as their domain, the > RTP proxy > will work as usual. > > If caller is not from iptel.org but callee is, then the SIP proxy will > pass IP of the NAT box (known from Contact in usrloc) and IP > from SDP of > INVITE to RTP proxy. The RTP proxy will be symmetric for the > NAT IP and > non-symmetric for the IP from SDP. > > In the reverse direction, i.e. when callee is not from iptel.org and > caller is (i.e. the invite is coming from iptel.org to fwd, for > example), the SIP proxy will pass IP from the received > parameter for the > "symmetric side" and IP from SDP of 200 OK for the > "non-symmetric part". > > That way it is not ensured that there is just one RTP proxy > along the path, > but it should work. > > In other words, every SIP proxy provides "symmetric RTP proxy" for its > users only, it doesn't provide it for foreign users. > > Drawback of this approach is that it is not possible to use > only one RTP > proxy in cases like: > > UA---NAT---Sipphone---iptel.org---NAT---UA > > In that case both Sipphone and iptel.org must enforce RTP proxy, each > proxy is responsible for getting their users through NAT. > > Anyway, implement and deploy something like that is quite complex. > > Jan. > > On 03-11 18:49, Klaus Darilion wrote: > > But if UA1 ist not behind NAT, proxy 2 should activated its > rtpproxy to > > enable a communciation although there are more than 2 Via headers. > > > > I guess there is no solution yet which will work in all > scenarios as one > > SIP proxy will never know the NAT-traversal strategy of > other proxies. > > > > regards, > > klaus > > > > > -----Original Message----- > > > From: Maxim Sobolev [mailto:sobomax@portaone.com] > > > Sent: Monday, November 03, 2003 6:40 PM > > > To: Jan Janak > > > Cc: Klaus Darilion; serusers(a)lists.iptel.org > > > Subject: Re: [Serusers] rtpproxy question > > > > > > > > > There is another possible solution: modify nathelper to only > > > apply RTP > > > proxy redirection if there is only one Via in the > request. This will > > > ensure that in the situation when there are multiple SIP/RTP > > > proxies in > > > the path only first one will handle RTP. Unfortunately it > > > will not help > > > if there are any SIP B2BUAs on the way. > > > > > > -Maxim > > > > > > Jan Janak wrote: > > > > On 03-11 19:18, Maxim Sobolev wrote: > > > > > > > >>Klaus Darilion wrote: > > > >> > > > >> > > > >>>Hi! > > > >>> > > > >>>As the RTP relaying does not work with 2 RTP proxies, how > > > can a proxy > > > >>>detect > > > >>>if the RTP stream is already redirected to an RTP proxy? > > > >>> > > > >>>My problem is the following scenario: > > > >>> > > > >>>UA1 --NAT-- SIP proxy 1 -- SIP proxy 2 --NAT-- UA2 > > > >>> rtpproxy1 rtpproxy2 > > > >>> > > > >>>UA1 invites UA2. SIP proxy 1 detects that UA1 is behind > > > NAT and enables the > > > >>>rtpproxy1 and forwards the invite to SIP proxy2. SIP proxy > > > 2 knows that UA2 > > > >>>is also behind NAT. Usually, SIP proxy 2 would activate > > > the rtpproxy2, but > > > >>>in this case this would not work as there is already an > > > rtpproxy involved. > > > >>>How can the SIP proxy 2 detect that the IP address in the > > > SDP is the IP > > > >>>address of an RTP proxy? > > > >>> > > > >>> > > > >> > > > >>Known problem. I think that I'll modify nathelper, so that > > > >>force_rtp_proxy() will insert some flag into the SDP body, > > > which will > > > >>tell other proxies along the request route that there is no > > > need to put > > > >>another RTP relay into the RTP path. > > > > > > > > > > > > Another option would be to insert a header field telling > > > that another > > > > RTP proxy is being used already. > > > > > > > > The problem is that both solutions (header field and SDP > > > flags) will > > > > be not interoperable. > > > > > > > > Another option would be to modify the RTP proxy so > that it will be > > > > symmetric only for user agents that belong to the domain > > > of the proxy. > > > > That would probably complicate things a bit. > > > > > > > > Jan. > > > > > > > > > > > > > > > > > > >