[Docs] [txt|pdf] [draft-ietf-sip- ] [Tracker] [Diff1] [Diff2] [IPR] PROPOSED STANDARD Network Working Group J. Rosenberg Request for Comments: . Network Working Group J. Rosenberg Request for Comments: dynamicsoft Category: Standards Track H. Schulzrinne Columbia University August Canonical URL: aralgocunes.ga; File formats: icon for text file icon for PDF icon for HTML; Status: PROPOSED STANDARD; Authors: J.
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RFC An Extension to the SIP for. Symmetric Response Routing. (rport: receive port parameter). Page 2. aralgocunes.ga 2. Signal Flow Diagram. Page 3. rfc pdf RFC DOWNLOAD Setting it to yes forces RFC behavior and enables symmetric RTP support. Setting it to no only enables RFC behavior if the . RFC SIP: Session Initiation Protocol (PS) Upd by RFC, RFC An Extension to SIP for Symmetric Response Routing (PS).
Event package for dialog state. In TS IMS allows any of the three mechanisms to be used, or combinations depending on circumstances.
All three mechanisms are transparent to proxy components, so supported by Clearwater. Also, need to proxy History-Info headers transparently. Clearwater supports this. However, s9. Clearwater does not currently do this so if other parts of the network are not compliant, Clearwater will not fill in for them and should. In IMS, this is only required for presence events, and is only mandatory for UEs supporting presence or presence servers, otherwise it is optional.
Should be transparent to proxies, so supported by Clearwater. Mandatory according to TS Reading Rel 9, this strongly suggests that the only nodes that need to actually invoke these mechanisms certain types of application servers, such as conference servers or message servers that support message distribution lists so the function is to guard against people being added to these lists without their consent.
Therefore the only function required in the core is to pass the messages and headers through transparently. Clearwater already supports this minimal set of function. The function is mandatory in an IMS message list server, but not required anywhere else in the network.
Mandatory for IMS conference app servers. One use case for this could be to send a single REFER to a conference server to get it to invite a group of people to a conference. This header is supported by Clearwater and included on requests sent to application servers. Supported by Clearwater for NAT traversal, except for the Flow-Timer header which tells the client how often to send keepalives.
Clearwater used RFC double-record routing in Bono nodes when transitioning between the trusted and untrusted zones on different port numbers. Transparent to proxies anyway, so supported by Clearwater. Framework for passing geo-location information within SIP messages. According to TS Supported by Clearwater as headers will be passed transparently. Clearwater will forward these headers if specified by other nodes in the signaling path, so this is supported.
Mandatory in proxy components according to TS Supported in Clearwater. You are welcome to post more questions or configuration or logs for other community members to look at but if your issue requires a fix via Polycom you must go via the official support structure. For the first it often helps to change the rfc to port preserving routerfor the latter the Auto or Always mode works better. The Rfc stack of the telephony system then discarded the packet rrfc the received Contact header was not the same as the sent one.
Leave a Reply Cancel reply Your email address will not be published. Such problems can only be found with a detailed look at network traces e. In this chapter some problems we had in ffc past are mentioned. No Rfc type detection is made. The called party sends new requests within the dialog directly to the peer the callere. In addition, the port rfc changed in many cases.
RFC PDF Everything is fine, until it happens that the port needs to be changed, because it is already in use rfc another host or was used before by the same host and the binding has not timed out yet. This Rfc type detection works with most, but not all routers that are available. This state information is called binding. These protocols allow a client behind a NAT to learn the IP address and port that a NAT will allocate for a particular request, in order to use this information in application layer protocols.
Using the "rport" parameter defined here and the "received" parameter defined in RFC [ 1 ] in the topmost Via header field value of a response, a client sending a request can learn its address as it was seen by the server which sent the response.
There are two uses of this information. The first is for registrations. The client must provide, in its registration, the address at which it should receive incoming SIP requests from the proxy. However, since the client is located behind a NAT, none of the addresses on any of its interfaces will be reachable from the proxy. If the client can provide the proxy with an address that the proxy can reach, the client can receive incoming requests. The client can then perform an additional registration, using this address in a Contact header.
In many cases, the server to whom the registration is sent won't be the registrar itself, but rather a proxy which then sends the request to the registrar.
In such a case, any incoming requests for the client must traverse the proxy to whom the registration was directly sent. The Path header extension to SIP [ 3 ] allows the proxy to indicate that it must be on the path of such requests. The second usage is for record routing, to address the same problem as above, but between two proxies.
This address can be placed into the Record-Route header field of requests sent to that server. Because of this potential usage, this document must consider the issues raised in [ 5 ]. A short term fix should not be generalized to solve other problems; this is why "short term fixes usually aren't". The better short term fixes are the ones that will naturally see less and less use as the appropriate technology is deployed.
The SIP working group has recognized that the usage of this specification to support registrations and record-routing through NATs is not appropriate.
It has a number of known problems which are documented below. The way to eliminate potential usage of this specification for address fixing is to provide a proper solution to the problems that might motivate the usage of this specification for address fixing. Specifically, appropriate solutions for registrations and record-routing in the presence of NATs need to be developed.
These solutions would not rely on address fixing. Requirements for such solutions are already under development [ 6 ]. Implementors of this specification are encouraged to follow this work for better solutions for registrations and record-routing through NAT. For example, approaches that involve using data at multiple network layers create more dependencies, increase debugging challenges, and make it harder to transition.
This specification, if used for address fixing, introduces several points of brittleness into a SIP system: o If used for UDP registrations, a client will need to frequently re-register in order to keep the NAT bindings fresh. In many cases, these registrations will need to take place nearly one hundred times more frequently than the typical refresh interval of a registration.
This introduces load into the system and hampers scalability. Therefore, there may be periods of unreachability that occur between the time a binding expires and the next registration or OPTIONS refresh is sent. This may result in missed calls, messages, or other information. If that server is one of many servers in a cluster, the client may not be able to receive requests from other servers in the cluster. This server behavior is not mandated by RFC [ 1 ], although it appears to be common in practice.
There is not an easy and reliable way for the server to determine that the Path header should be used for a registration. Using Path when the address in the topmost Via header field is a private address will usually work, but may result in usage of Path when it is not actually needed.
Requirements for a Long Term Solution From [ 5 ], any UNSAF proposal must provide: Identify requirements for longer term, sound technical solutions -- contribute to the process of finding the right longer term solution.
The brittleness described in Section 9. Registrations and record routing require the client to specify the address at which it should receive requests.
A sound technical solution should allow a client to explicitly specify that it wants to receive incoming requests on the connection over which the outgoing request was sent.
In this way, the client does not need to specify its address. The solution must deal with clusters of servers. In many commercially deployed SIP systems, there will be multiple servers, each at different addresses and ports, handling incoming requests for a client.
The solution must explicitly consider this case. The solution must not require increases in network load. There cannot be a penalty for a sound technical solution.