Push Notification with the Session Initiation Protocol (SIP)
RFC 8599
| Document | Type | RFC - Proposed Standard (May 2019) Errata | |
|---|---|---|---|
| Authors | Christer Holmberg , Michael Arnold | ||
| Last updated | 2022-09-20 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| IESG | Responsible AD | Ben Campbell | |
| Send notices to | (None) |
RFC 8599
RFC 8599 SIP PUSH May 2019 When a proxy receives a 2xx response to the REGISTER request, if the proxy had indicated support of one or more types of PNSs in the REGISTER request (see above), the proxy MUST indicate support of the same set of types of PNSs in the response. In addition, if the proxy supports the VAPID mechanism for one or more types of PNSs, the proxy MUST indicate support of the mechanism for those PNSs in the response. 5.6.2. Initial Request for Dialog or Standalone Request The procedures in this section apply when a SIP proxy has indicated that it will request that push notifications are sent to the SIP UA. When the proxy receives a SIP request for a new dialog (e.g., a SIP INVITE request) or a standalone SIP request (e.g., a SIP MESSAGE request) addressed towards a SIP UA, if the Request-URI of the request contains a 'pn-provider', a 'pn-prid', and a 'pn-param' (if required for the specific PNS provider) SIP URI parameter, the proxy requests that a push notification be sent to the UA using the information in the 'pn-*' SIP URI parameters. The proxy then places the SIP request in the SIP Request Push Bucket. The push notification will trigger the UA to send a binding-refresh REGISTER request that the proxy will process as described in Section 5.6.1. In addition, the proxy MUST store the Contact URI of the REGISTER request during the lifetime of the REGISTER transaction. NOTE: If the proxy receives a SIP request that does not contain the 'pn-*' SIP URI parameters listed above, the proxy processing of the request is based on local policy. If the proxy also serves requests for UAs that do not use the SIP push mechanism, the proxy can forward the request towards the UA. Otherwise, the proxy can reject the request. When the proxy receives a 2xx response to the REGISTER request, the proxy performs the following actions: o The proxy processes the REGISTER response as described in Section 5.6.1. o The proxy checks whether the SIP Request Push Bucket contains a SIP request associated with the REGISTER transaction by comparing (Section 5.3) the Contact header field URI in the REGISTER response with the Request-URIs of the SIP requests in the bucket. If there is a match, the proxy MUST remove the SIP request from the bucket and forward it towards the UA. Holmberg & Arnold Standards Track [Page 20] RFC 8599 SIP PUSH May 2019 The reason the proxy needs to wait for the REGISTER response before forwarding a SIP request towards a UA is to make sure that the REGISTER request has been accepted by the registrar, and that the UA that initiated the REGISTER request is authorized to receive messages for the Request-URI. If the proxy receives a non-2xx response to the REGISTER request, the proxy compares the Contact URI stored from the REGISTER request (see above) with the Request-URIs of the SIP requests in the SIP Request Push Bucket. If there is a match, the proxy SHOULD remove the associated request from the bucket and send an error response to the request. It is RECOMMENDED that the proxy sends either a 404 (Not Found) response or a 480 (Temporarily Unavailable) response to the SIP request, but other response codes can be used as well. However, if the REGISTER response is expected to trigger a new REGISTER request from the UA (e.g., if the registrar is requesting the UA to perform authentication), the proxy MAY keep the SIP request in the bucket. If the push notification request fails (see PNS-specific documentation for details), the proxy MUST remove the SIP request from the bucket and send an error response to the SIP request. It is RECOMMENDED that the proxy sends either a 404 (Not Found) response or a 480 (Temporarily Unavailable) response, but other response codes can be used as well. After the proxy has requested that a push notification be sent to a UA, if the proxy does not receive a REGISTER response with a Contact URI that matches the Request-URI of the SIP request before the Bucket Timer (Section 5.2) associated with the SIP request times out, the proxy MUST remove the SIP request from the SIP Request Push Bucket (Section 5.2) and send a 480 (Temporarily Unavailable) response. The Bucket Timer time-out value is set based on local policy, taking the guidelines below into consideration. As discussed in [RFC4320] and [RFC4321], non-INVITE transactions must complete immediately or risk losing a race, which results in stress on intermediaries and state misalignment at the endpoints. The mechanism defined in this document inherently delays the final response to any non-INVITE request that requires a push notification. In particular, if the proxy forwards the SIP request towards the SIP UA, the SIP UA accepts the request, but the transaction times out at the sender before it receives the successful response, this will cause state misalignment between the endpoints (the sender considers the transaction a failure, while the receiver considers the transaction a success). The SIP proxy needs to take this into account when it sets the value of the Bucket Timer associated with the transaction, to make sure that the error response (triggered by a Holmberg & Arnold Standards Track [Page 21] RFC 8599 SIP PUSH May 2019 Bucket Timer time out) reaches the sender before the transaction times out. If the accumulated delay of this mechanism combined with any other mechanisms in the path of processing the non-INVITE transaction cannot be kept short, this mechanism should not be used. For networks encountering such conditions, an alternative (left for possible future work) would be for the proxy to immediately return a new error code meaning "wait at least the number of seconds specified in this response and retry your request" before initiating the push notification. NOTE: While the work on this document was ongoing, implementation test results showed that the time it takes for a proxy to receive the REGISTER request, from when the proxy has requested a push notification, is typically around 2 seconds. However, the time might vary depending on the characteristics and load of the SIP network and the PNS. In addition to the procedures described above, there are two cases where a proxy, as an optimization, can forward a SIP request towards a UA without either waiting for a 2xx response to a REGISTER request or requesting that a push notification be sent to the UA: o If the proxy is able to authenticate the sender of the REGISTER request and verify that it is allowed by authorization policy, the proxy does not need to wait for the 2xx response before it forwards the SIP request towards the UA. In such cases, the proxy will use the Contact URI of the REGISTER request when comparing it against the Request-URIs of the SIP requests in the SIP Request Push Bucket. o If the proxy has knowledge that the UA is awake, and that the UA is able to receive the SIP request without first sending a binding-refresh REGISTER request, the proxy does not need to request that a push notification be sent to the UA (the UA will not send a binding-refresh REGISTER request) before it forwards the SIP request towards the UA. The mechanisms for getting such knowledge might be dependent on implementation or deployment architecture, and are outside the scope of this document. Some PNS providers allow payload in the push notifications. This specification does not define usage of such payload (in addition to any payload that might be required by the PNS itself). Holmberg & Arnold Standards Track [Page 22] RFC 8599 SIP PUSH May 2019 6. Support of Long-Lived SIP Dialogs Some SIP dialogs might have a long lifetime with little activity. For example, when the SIP event notification mechanism [RFC6665] is used, there might be a long period between the sending of mid-dialog requests. Because of this, a SIP UA may be suspended and may need to be awakened in order to be able to receive mid-dialog requests. SIP requests for a new dialog and standalone SIP requests addressed towards a UA with 'pn-*' SIP URI parameters allow the proxy to request that a push notification be sent to the UA (Section 5.6.2). However, 'pn-*' SIP URI parameters will not be present in mid-dialog requests addressed towards the UA. Instead, the proxy needs to support a mechanism to store the information needed to request that a push notification be sent to the UA, and to be able to retrieve that information when it receives a mid-dialog request addressed towards the UA. This section defines such a mechanism. The SIP UA and SIP proxy procedures in this section are applied in addition to the generic procedures defined in this specification. +--------+ +---------+ +-----------+ +-------------+ | | | | | | | SIP | | SIP UA | | Push | | SIP Proxy | | Registrar / | | | | Service | | | | Home Proxy | +--------+ +---------+ +-----------+ +-------------+ | | | | | PNS Register | | | |---------------->| | | | | | | | PRID | | | |<----------------| | | | | | | | SIP REGISTER (PRID) | | |===================================>| | | | |SIP REGISTER (PRID)| | | |==================>| | | | | | | +-----------------------+ | | | | Store PRID (key=PURR) | | | | +-----------------------+ | | | | | | | | SIP 200 OK | | | |<==================| | SIP 200 OK (PURR) | | |<===================================| | | | | | | | | | Holmberg & Arnold Standards Track [Page 23] RFC 8599 SIP PUSH May 2019 | SIP INVITE (PURR) | | |===================================>| | | | |SIP INVITE (PURR) | | | |==================>| | | | | | | | SIP 200 OK | | | |<==================| | SIP 200 OK | | | |<===================================| | | | | | | | | | | | | | | | |SIP UPDATE (PURR) | | | |<==================| | | | | | | +-----------------------+ | | | | Fetch PRID (key=PURR) | | | | +-----------------------+ | | | | | | |Push Request (PRID) | | |<-----------------| | |Push Message (PRID) | | |<----------------| | | | | | | | SIP REGISTER (PRID) | | |===================================>| | | | |SIP REGISTER (PRID)| | | |==================>| | | | | | | | SIP 200 OK | | | |<==================| | SIP 200 OK (PURR) | | |<===================================| | | | | | | SIP UPDATE | | | |<===================================| | | | | | ------- Push Notification API ======= SIP Figure 4: SIP Push Long-Lived Dialog Flow Holmberg & Arnold Standards Track [Page 24] RFC 8599 SIP PUSH May 2019 6.1. SIP UA Behavior 6.1.1. Initial Request for Dialog If the UA is willing to receive push notifications when a proxy receives a mid-dialog request addressed towards the UA, the UA MUST insert a 'pn-purr' SIP URI parameter (Section 6.2.1) in the Contact header field URI of the initial request for a dialog or the 2xx response to such requests. The UA MUST insert a parameter value identical to the last 'sip.pnspurr' feature-capability indicator (Section 6.2.1) that it received in a REGISTER response. If the UA has not received a 'sip.pnspurr' feature-capability indicator, the UA MUST NOT insert a 'pn-purr' SIP URI parameter in a request or response. The UA makes the decision to receive push notifications triggered by incoming mid-dialog requests based on local policy. Such policy might be based on the type of SIP dialog, the type of media (if any) negotiated for the dialog [RFC3264], etc. NOTE: As the 'pn-purr' SIP URI parameter only applies to a given dialog, the UA needs to insert a 'pn-purr' parameter in the Contact header field URI of the request or response for each dialog in which the UA is willing to receive push notifications triggered by incoming mid-dialog requests. 6.2. SIP Proxy Behavior 6.2.1. REGISTER If the proxy supports requesting push notifications triggered by mid- dialog requests being sent to the registered UA, the proxy MUST store the information (the 'pn-*' SIP URI parameters) needed to request that push notifications are sent to the UA when a proxy receives an initial REGISTER request for a binding from the UA. In addition, the proxy MUST generate a unique (within the context of the proxy) value, referred to as the PURR (Proxy Unique Registration Reference), that can be used as a key to retrieve the information. In order to prevent client fingerprinting, the proxy MUST periodically generate a new PURR value (even if 'pn-*'parameters did not change). However, as long as there are ongoing dialogs associated with the old value, the proxy MUST store it so that it can request that push notifications are sent to the UA when it receives a mid-dialog request addressed towards the UA. In addition, the PURR value MUST be generated in such a way so that it is unforgeable, anonymous, and unlinkable to entities other than the proxy. It must not be possible for an attacker to generate a valid PURR, to Holmberg & Arnold Standards Track [Page 25] RFC 8599 SIP PUSH May 2019 associate a PURR with a specific user, or to determine when two PURRs correspond to the same user. It can be generated, e.g., by utilizing a cryptographically secure random function with an appropriately large output size. Whenever the proxy receives a 2xx response to a REGISTER request, the proxy MUST insert a 'sip.pnspurr' feature-capability indicator with the latest PURR value (see above) in the response. 6.2.2. Initial Request for Dialog When a proxy receives an initial request for a dialog from a UA that contains a 'pn-purr' SIP URI parameter in the Contact header field URI with a PURR value that the proxy has generated (Section 6.2.1), the proxy MUST add a Record-Route header to the request to insert itself in the dialog route [RFC3261] before forwarding the request. When the proxy receives an initial request for a dialog addressed towards the UA, and the proxy has generated a PURR value associated with the 'pn-*' parameters inserted in the SIP URI of the request (Section 6.2.2), the proxy MUST add a Record-Route header to the request to insert itself in the dialog route [RFC3261] before forwarding the request. 6.2.3. Mid-dialog Request When the proxy receives a mid-dialog SIP request addressed towards the UA that contains a 'pn-purr' SIP URI parameter, and the proxy is able to retrieve the stored information needed to request that a push notification be sent to the UA (Section 6.2.1), the proxy MUST place the SIP request in the SIP Request Push Bucket and request that a push notification be sent to the UA. NOTE: The 'pn-purr' SIP URI parameter will either be carried in the Request-URI or in a Route header field [RFC3261] of the SIP request depending on how the route set [RFC3261] of the mid-dialog SIP request has been constructed. When the proxy receives a 2xx response to a REGISTER request, the proxy checks whether the SIP Request Push Bucket contains a mid- dialog SIP request associated with the REGISTER transaction. If the bucket contains such a request, the proxy MUST remove the SIP request from the SIP Request Push Bucket and forward it towards the UA. Note that the proxy does not perform a URI comparison (Section 5.3) when processing mid-dialog requests, as a mid-dialog request will not contain the 'pn-prid', 'pn-provider', and 'pn-param' SIP URI Holmberg & Arnold Standards Track [Page 26] RFC 8599 SIP PUSH May 2019 parameters. The proxy only checks for a mid-dialog request that contains the PURR value associated with the REGISTER 2xx response. As described in Section 5.6.2, while waiting for the push notification request to succeed, and then for the associated REGISTER request and 2xx response, the proxy needs to take into consideration that the transaction associated with the mid-dialog request will eventually time out at the sender of the request (User Agent Client), and the sender will consider the transaction a failure. When a proxy sends an error response to a mid-dialog request (e.g., due to a transaction time out), the proxy SHOULD select a response code that only impacts the transaction associated with the request [RFC5079]. 7. Support of SIP Replaces [RFC3891] defines a mechanism that allows a SIP UA to replace a dialog with another dialog. A UA that wants to replace a dialog with another one will send an initial request for the new dialog. The Request-URI of the request will contain the Contact header field URI of the peer. If a SIP proxy wants to be able to request that a push notification be sent to a UA when it receives an initial request for a dialog that replaces an existing dialog, using the mechanism in [RFC3891], the proxy and the UA MUST perform the following actions: o The proxy MUST provide a PURR to the UA during registration (Section 6.2.1). o The UA MUST insert a 'pn-purr' SIP URI parameter in the Contact header field URI of either the initial request for a dialog or a 2xx response to such requests (Section 6.1.1). This includes dialogs replacing other dialogs, as those dialogs might also get replaced. o The proxy MUST apply the mechanism defined in Section 6.2.3 to place and retrieve the request from the SIP Request Push Bucket. In addition, the operator needs to make sure that the initial request for dialogs, addressed towards the UA using the contact of the replaced dialog, will be routed to the SIP proxy (in order to request that a push notification be sent to the UA). The procedures for doing that are operator-specific and are outside the scope of this specification. Holmberg & Arnold Standards Track [Page 27] RFC 8599 SIP PUSH May 2019 8. Grammar 8.1. 555 (Push Notification Service Not Supported) Response Code The 555 response code is added to the "Server-Error" Status-Code definition. 555 (Push Notification Service Not Supported) is used to indicate that the server does not support the push notification service identified in a 'pn-provider' SIP URI parameter. The use of the SIP 555 response code is only defined for SIP REGISTER responses. 8.2. 'sip.pns' Feature-Capability Indicator The sip.pns feature-capability indicator, when inserted in a Feature- Caps header field of a SIP REGISTER request or a SIP 2xx response to a REGISTER request, indicates that the entity associated with the indicator supports the SIP push mechanism and the type of push notification service indicated by the indicator value. The values defined for the 'pn-provider' SIP URI parameter are used as indicator values. pns-fc = "+sip.pns" EQUAL LDQUOT pns RDQUOT pns = tag-value tag-value = <tag-value defined in [RFC3840]> 8.3. 'sip.vapid' Feature-Capability Indicator The sip.vapid feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, denotes that the entity associated with the indicator supports the Voluntary Application Server Identification (VAPID) [RFC8292] mechanism when the entity requests that a push notification be sent to a SIP UA. The indicator value is a public key identifying the entity that can be used by a SIP UA to restrict subscriptions to that entity. vapid-fc = "+sip.vapid" EQUAL LDQUOT vapid RDQUOT vapid = tag-value tag-value = <tag-value defined in [RFC3840]> 8.4. 'sip.pnsreg' Feature-Capability Indicator The sip.pnsreg feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, denotes that the entity associated with the indicator expects to receive binding-refresh REGISTER requests from the SIP UA associated with the binding before Holmberg & Arnold Standards Track [Page 28] RFC 8599 SIP PUSH May 2019 the binding expires, even if the entity does not request that a push notification be sent to the SIP UA in order to trigger the binding- refresh REGISTER requests. The indicator value conveys the minimum time (given in seconds) prior to the binding expiration when the UA MUST send the REGISTER request. pns-fc = "+sip.pnsreg" EQUAL LDQUOT reg RDQUOT reg = 1*DIGIT DIGIT = <DIGIT defined in [RFC3261]> 8.5. 'sip.pnsreg' Media Feature Tag The sip.pnsreg media feature tag, when inserted in the Contact header field of a SIP REGISTER request, indicates that the SIP UA associated with the tag is able to send binding-refresh REGISTER requests for the associated binding without being awakened by push notifications. The media feature tag has no values. pnsreg-mt = "+sip.pnsreg" 8.6. 'sip.pnspurr' Feature-Capability Indicator The sip.pnspurr feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, denotes that the entity associated with the indicator will store information that can be used to associate a mid-dialog SIP request with the binding information in the REGISTER request. pnspurr-fc = "+sip.pnspurr" EQUAL LDQUOT pnspurr RDQUOT pnspurr = tag-value tag-value = <tag-value defined in [RFC3840]> 8.7. SIP URI Parameters This section defines new SIP URI parameters by extending the grammar for "uri-parameter" as defined in [RFC3261]. The ABNF [RFC5234] is as follows: uri-parameter =/ pn-provider / pn-param / pn-prid / pn-purr pn-provider = "pn-provider" [EQUAL pvalue] pn-param = "pn-param" EQUAL pvalue pn-prid = "pn-prid" EQUAL pvalue pn-purr = "pn-purr" EQUAL pvalue pvalue = <pvalue defined in [RFC3261]> EQUAL = <EQUAL defined in [RFC3261]> Holmberg & Arnold Standards Track [Page 29] RFC 8599 SIP PUSH May 2019 The format and semantics of pn-prid and pn-param are specific to the pn-provider value. Parameter value characters that are not part of pvalue need to be escaped, as defined in RFC 3261. 9. PNS Registration Requirements When a new value is registered to the PNS subregistry, a reference to a specification that describes the usage of the PNS associated with the value is provided. That specification MUST contain the following information: o The value of the 'pn-provider' SIP URI parameter. o How the 'pn-prid' SIP URI parameter value is retrieved and set by the SIP UA. o How the 'pn-param' SIP URI parameter (if required for the specific PNS provider) value is retrieved and set by the SIP UA. 10. 'pn-provider', 'pn-param', and 'pn-prid' URI Parameters for Apple Push Notification service When the Apple Push Notification service (APNs) is used, the PNS-related SIP URI parameters are set as described below. For detailed information about the parameter values, see <https://developer.apple.com/library/archive/documentation/ NetworkingInternet/Conceptual/RemoteNotificationsPG/ CommunicatingwithAPNs.html> [pns-apns]. The value of the 'pn-provider' URI parameter is "apns". Example: pn-provider=apns The value of the 'pn-param' URI parameter is a string that is composed of two values separated by a period (.): Team ID and Topic. The Team ID is provided by Apple and is unique to a development team. The Topic consists of the Bundle ID, which uniquely identifies an application, and a service value that identifies a service associated with the application, separated by a period (.). For Voice over IP (VoIP) applications, the service value is "voip". Example: pn-param=DEF123GHIJ.com.example.yourexampleapp.voip Holmberg & Arnold Standards Track [Page 30] RFC 8599 SIP PUSH May 2019 NOTE: The Bundle ID might contain one or more periods (.). Hence, within the 'pn-param' value, the first period will be separating the Team ID from the Topic, and within the Topic, the last period will be separating the Bundle ID from the service. The value of the 'pn-prid' URI parameter is the device token, which is a unique identifier assigned by Apple to a specific app on a specific device. Example: pn-prid=00fc13adff78512 11. 'pn-provider', 'pn-param', and 'pn-prid' URI Parameters for Google Firebase Cloud Messaging (FCM) Push Notification Service When Firebase Cloud Messaging (FCM) is used, the PNS-related URI parameters are set as described below. For detailed information about the parameter values, see <https://firebase.google.com/docs/cloud-messaging/concept-options> [pns-fcm]. The value of the 'pn-provider' URI parameter is "fcm". The value of the 'pn-param' URI parameter is the Project ID. The value of the 'pn-prid' URI parameter is the Registration token, which is generated by the FCM SDK for each client app instance. 12. 'pn-provider', 'pn-param', and 'pn-prid' URI Parameters for RFC 8030 (Generic Event Delivery Using HTTP Push) When Generic Event Delivery Using HTTP Push is used, the PNS-related URI parameters are set as described below. The value of the 'pn-provider' URI parameter is "webpush". The value of the 'pn-param' URI parameter MUST NOT be used. The value of the 'pn-prid' URI parameter is the push subscription URI. See RFC 8030 [RFC8030] for more details. Note that encryption for web push [RFC8291] is not used; therefore, parameters for message encryption are not defined in this specification. Web push permits the sending of a push message without a payload without encryption. Holmberg & Arnold Standards Track [Page 31] RFC 8599 SIP PUSH May 2019 13. Security Considerations The security considerations for the use and operation of any particular PNS (e.g., how users and devices are authenticated and authorized) are out of scope for this document. [RFC8030] documents the security considerations for the PNS defined in that specification. Security considerations for other PNSs are left to their respective specifications. Typically, the PNS requires the SIP proxy requesting push notifications to be authenticated and authorized by the PNS. In some cases, the PNS also requires the SIP application (or the SIP application developer) to be identified in order for the application to request push notifications. Unless the PNS authenticates and authorizes the PNS, a malicious endpoint or network entity that managed to get access to the parameters transported in the SIP signaling might be able to request that push notifications are sent to a UA. Such push notifications will impact the battery life of the UA and trigger unnecessary SIP traffic. [RFC8292] defines a mechanism that allows a proxy to identify itself to a PNS by signing a JSON Web Token (JWT) sent to the PNS using a key pair. The public key serves as an identifier of the proxy and can be used by devices to restrict push notifications to the proxy associated with the key. Operators MUST ensure that the SIP signaling is properly secured, e.g., using encryption, from malicious network entities. TLS MUST be used unless the operators know that the signaling is secured using some other mechanism that provides strong crypto properties. In addition to the information that needs to be exchanged between a device and the PNS in order to establish a push notification subscription, the mechanism defined in this document does not require any additional information to be exchanged between the device and the PNS. The mechanism defined in this document does not require a proxy to insert any payload (in addition to possible payload used for the PNS itself) when requesting push notifications. Operators MUST ensure that the PNS-related SIP URI parameters conveyed by a user in the Contact URI of a REGISTER request are not sent to other users or to non-trusted network entities. One way to convey contact information is by using the SIP event package for registrations mechanism [RFC3680]. [RFC3680] defines generic security considerations for the SIP event package for registrations. As the PNS-related SIP URI parameters conveyed in the REGISTER Holmberg & Arnold Standards Track [Page 32] RFC 8599 SIP PUSH May 2019 request contain sensitive information, operators that support the event package MUST ensure that event package subscriptions are properly authenticated and authorized, and that the SIP URI parameters are not inserted in event notifications sent to other users or to non-trusted network entities. 14. IANA Considerations 14.1. SIP URI Parameters This section defines new SIP URI Parameters that extend the "SIP/SIPS URI Parameters" subregistry [RFC3969] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). 14.1.1. pn-provider Parameter Name: pn-provider Predefined Values: No Reference: RFC 8599 14.1.2. pn-param Parameter Name: pn-param Predefined Values: No Reference: RFC 8599 14.1.3. pn-prid Parameter Name: pn-prid Predefined Values: No Reference: RFC 8599 14.1.4. pn-purr Parameter Name: pn-purr Predefined Values: No Reference: RFC 8599 Holmberg & Arnold Standards Track [Page 33] RFC 8599 SIP PUSH May 2019 14.2. SIP Response Codes 14.2.1. 555 (Push Notification Service Not Supported) This section defines a new SIP response code that extends the "Response Codes" subregistry [RFC3261] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). Response Code Number: 555 Default Reason Phrase: Push Notification Service Not Supported 14.3. SIP Global Feature-Capability Indicator 14.3.1. sip.pns This section defines a new feature-capability indicator that extends the "SIP Feature-Capability Indicator Registration Tree" subregistry [RFC6809] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). Name: sip.pns Description: This feature-capability indicator, when inserted in a Feature-Caps header field of a SIP REGISTER request or a SIP 2xx response to a REGISTER request, denotes that the entity associated with the indicator supports the SIP push mechanism and the type of push notification service conveyed by the indicator value. Reference: RFC 8599 Contact: IESG (iesg@ietf.org) 14.3.2. sip.vapid This section defines a new feature-capability indicator that extends the "SIP Feature-Capability Indicator Registration Tree" subregistry [RFC6809] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). Name: sip.vapid Description: This feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, denotes that the entity associated with the indicator supports the Voluntary Application Server Identification (VAPID) mechanism when the entity requests that a push notification be sent to a SIP UA. Holmberg & Arnold Standards Track [Page 34] RFC 8599 SIP PUSH May 2019 The indicator value is a public key identifying the entity, which can be used by a SIP UA to restrict subscriptions to that entity. Reference: RFC 8599 Contact: IESG (iesg@ietf.org) 14.3.3. sip.pnsreg This section defines a new feature-capability indicator that extends the "SIP Feature-Capability Indicator Registration Tree" subregistry [RFC6809] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). Name: sip.pnsreg Description: This feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, denotes that the entity associated with the indicator expects to receive binding-refresh REGISTER requests for the binding from the SIP UA associated with the binding before the binding expires, even if the entity does not request that a push notification be sent to the SIP UA in order to trigger the binding-refresh REGISTER requests. The indicator value conveys the minimum time (given in seconds) prior to the binding expiration when the UA MUST send the REGISTER request. Reference: RFC 8599 Contact: IESG (iesg@ietf.org) 14.3.4. sip.pnspurr This section defines a new feature-capability indicator that extends the "SIP Feature-Capability Indicator Registration Tree" subregistry [RFC6809] under the SIP Parameters registry (https://www.iana.org/assignments/sip-parameters). Name: sip.pnspurr Description: This feature-capability indicator, when inserted in a SIP 2xx response to a SIP REGISTER request, conveys that the entity associated with the indicator will store information that can be used to associate a mid-dialog SIP request with the binding information in the REGISTER request. The indicator value is an identifier that can be used as a key to retrieve the binding information. Holmberg & Arnold Standards Track [Page 35] RFC 8599 SIP PUSH May 2019 Reference: RFC 8599 Contact: IESG (iesg@ietf.org) 14.4. SIP Media Feature Tag 14.4.1. sip.pnsreg This section defines a new media feature tag that extends the "SIP Media Feature Tag Registration Tree" subregistry [RFC3840] under the "Media Feature Tags" registry (https://www.iana.org/assignments/ media-feature-tags). Media feature tag name: sip.pnsreg Summary of the media feature indicated by this feature tag: This media feature tag, when inserted in the Contact header field of a SIP REGISTER request, conveys that the SIP UA associated with the tag is able to send binding-refresh REGISTER requests associated with the registration without being awakened by push notifications. Values appropriate for use with this feature tag: none Related standards or documents: RFC 8599 Security considerations: This media feature tag does not introduce new security considerations, as it simply indicates support for a basic SIP feature. If an attacker manages to remove the media feature tag, push notifications will not be requested to be sent to the client. Contact: IESG (iesg@ietf.org) 14.5. PNS Subregistry Establishment This section creates a new subregistry, "PNS", under the SIP Parameters registry (https://www.iana.org/assignments/ sip-parameters). The purpose of the subregistry is to register SIP URI 'pn-provider' values. When a SIP URI 'pn-provider' value is registered in the subregistry, it needs to meet the "Specification Required" policies defined in [RFC8126]. Holmberg & Arnold Standards Track [Page 36] RFC 8599 SIP PUSH May 2019 This subregistry is defined as a table that contains the following three columns: Value: The token under registration Description: The name of the Push Notification Service (PNS) Document: A reference to the document defining the registration This specification registers the following values: Value Description Document ------- -------------------------------------- ---------- apns Apple Push Notification service RFC 8599 fcm Firebase Cloud Messaging RFC 8599 webpush Generic Event Delivery Using HTTP Push RFC 8599 15. References 15.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, <https://www.rfc-editor.org/info/rfc3261>. [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, DOI 10.17487/RFC3840, August 2004, <https://www.rfc-editor.org/info/rfc3840>. [RFC3891] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation Protocol (SIP) "Replaces" Header", RFC 3891, DOI 10.17487/RFC3891, September 2004, <https://www.rfc-editor.org/info/rfc3891>. Holmberg & Arnold Standards Track [Page 37] RFC 8599 SIP PUSH May 2019 [RFC3969] Camarillo, G., "The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)", BCP 99, RFC 3969, DOI 10.17487/RFC3969, December 2004, <https://www.rfc-editor.org/info/rfc3969>. [RFC5079] Rosenberg, J., "Rejecting Anonymous Requests in the Session Initiation Protocol (SIP)", RFC 5079, DOI 10.17487/RFC5079, December 2007, <https://www.rfc-editor.org/info/rfc5079>. [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, <https://www.rfc-editor.org/info/rfc5234>. [RFC6809] Holmberg, C., Sedlacek, I., and H. Kaplan, "Mechanism to Indicate Support of Features and Capabilities in the Session Initiation Protocol (SIP)", RFC 6809, DOI 10.17487/RFC6809, November 2012, <https://www.rfc-editor.org/info/rfc6809>. [RFC8030] Thomson, M., Damaggio, E., and B. Raymor, Ed., "Generic Event Delivery Using HTTP Push", RFC 8030, DOI 10.17487/RFC8030, December 2016, <https://www.rfc-editor.org/info/rfc8030>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [RFC8292] Thomson, M. and P. Beverloo, "Voluntary Application Server Identification (VAPID) for Web Push", RFC 8292, DOI 10.17487/RFC8292, November 2017, <https://www.rfc-editor.org/info/rfc8292>. [pns-apns] Apple Inc., "Local and Remote Notification Programming Guide: Communicating with APNs", <https://developer.apple. com/library/archive/documentation/NetworkingInternet/Conce ptual/RemoteNotificationsPG/CommunicatingwithAPNs.html>. [pns-fcm] Google Inc., "Firebase Cloud Messaging", <https://firebase.google.com/docs/cloud-messaging/ concept-options>. Holmberg & Arnold Standards Track [Page 38] RFC 8599 SIP PUSH May 2019 15.2. Informative References [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, DOI 10.17487/RFC3264, June 2002, <https://www.rfc-editor.org/info/rfc3264>. [RFC3680] Rosenberg, J., "A Session Initiation Protocol (SIP) Event Package for Registrations", RFC 3680, DOI 10.17487/RFC3680, March 2004, <https://www.rfc-editor.org/info/rfc3680>. [RFC4320] Sparks, R., "Actions Addressing Identified Issues with the Session Initiation Protocol's (SIP) Non-INVITE Transaction", RFC 4320, DOI 10.17487/RFC4320, January 2006, <https://www.rfc-editor.org/info/rfc4320>. [RFC4321] Sparks, R., "Problems Identified Associated with the Session Initiation Protocol's (SIP) Non-INVITE Transaction", RFC 4321, DOI 10.17487/RFC4321, January 2006, <https://www.rfc-editor.org/info/rfc4321>. [RFC5626] Jennings, C., Ed., Mahy, R., Ed., and F. Audet, Ed., "Managing Client-Initiated Connections in the Session Initiation Protocol (SIP)", RFC 5626, DOI 10.17487/RFC5626, October 2009, <https://www.rfc-editor.org/info/rfc5626>. [RFC6665] Roach, A., "SIP-Specific Event Notification", RFC 6665, DOI 10.17487/RFC6665, July 2012, <https://www.rfc-editor.org/info/rfc6665>. [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. [RFC8291] Thomson, M., "Message Encryption for Web Push", RFC 8291, DOI 10.17487/RFC8291, November 2017, <https://www.rfc-editor.org/info/rfc8291>. Holmberg & Arnold Standards Track [Page 39] RFC 8599 SIP PUSH May 2019 Acknowledgements Thanks to Paul Kyzivat, Dale Worley, Ranjit Avasarala, Martin Thomson, Mikael Klein, Susanna Sjoholm, Kari-Pekka Perttula, Liviu Chircu, Roman Shpount, Yehoshua Gev, and Jean Mahoney for reading the text and providing useful feedback. Authors' Addresses Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: christer.holmberg@ericsson.com Michael Arnold Metaswitch Networks 100 Church Street Enfield EN2 6BQ United Kingdom Email: Michael.Arnold@metaswitch.com Holmberg & Arnold Standards Track [Page 40]