Avoiding Registration Storms by adapted Registration Behavior for Voice Cloud Applications
draft-schott-sip-avors-02
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Roland Schott , Michael Kreipl , Bastian Dreyer , Roland Jesske | ||
| Last updated | 2024-09-19 | ||
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draft-schott-sip-avors-02
ART R. Schott
Internet-Draft M. Kreipl
Intended status: Informational B. Dreyer
Expires: 23 March 2025 R. Jesske
Deutsche Telekom
19 September 2024
Avoiding Registration Storms by adapted Registration Behavior for Voice
Cloud Applications
draft-schott-sip-avors-02
Abstract
This document describes the AVORS (Avoiding Registration Storms)
concept that allows the resumption of active UE (User Equipment)
registrations on other SIP Proxies within the SIP voice architecture.
The concept can be mapped on any architecture having a distributed
structure and could work for different protocols. In this document,
the concept is exemplary explained regarding an architecture for
voice and could also be mapped on a 3GPP (3rd Generation Partnership
Project) architecture. The AVORS concept increases service
continuity, improves network resilience and offers savings potential.
Additionally, this document gives an outlook regarding stateless
voice architectures, load calculation aspects, and Service Based
Interfaces (SBI) with session data base interworking. Security
aspects are considered in the security chapter. As stated above the
AVORS principle is not only limited to the SIP protocol and could be
adopted by other protocols.
Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 23 March 2025.
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Rationale of the usage of AVORS mode for SIP sessions . . . . 4
4. Architecture Overview of AVORS Concept . . . . . . . . . . . 4
5. AVORS Procedure for SIP . . . . . . . . . . . . . . . . . . . 7
6. Functions of Registration Resumption Feature . . . . . . . . 10
7. Related work . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Security and operational considerations . . . . . . . . . . . 10
9. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 10
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
12.1. Normative References . . . . . . . . . . . . . . . . . . 11
12.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The AVORS "Avoiding Registration Storms" concept in context of SIP
and IMS (IP-Multimedia Subsystem) respectively helps, as the name
suggests, to reduce registration storms in case of an outage
especially site outages. Nowadays, registration storms are mitigated
by overcapacity. This overcapacity can be used by other
applications, if applicable or it is idling until an outage occurs.
The idling is causing electricity cost even in the case of
intelligent power management. In stateless architectures the
registration context is stored in a session data base and normally
all instances could access this session data base. According to
[TS_23.228] Service Based Architecture (SBA) and Service Based
Interfaces (SBI) offer in principal access to the session data base
for voice cloud-based applications. Regarding the current
standardized registration behavior the UE (User Equipment) MUST
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initiate a new initial registration. This registration needs to pass
the outbound proxy (SIP Proxy) and the registrar (SIP Server) before
reaching the data base. With the AVORS principle the outbound proxy
(SIP Proxy) has a dip into the session data base and recognizes that
a UE is already registered and is able to resume the registration.
Resuming of a registration of a session is feasible because the
registration session context can be stored in a session data base.
Instead of sending an initial registration in case of an outage the
UE will send a re-register message to the secondary outbound proxy
namely a failover SIP Proxy. This SIP Proxy could be a geo-redundant
one. The latter is able to retrieve the session information out of
the session data base and is able to resume the registration without
sending the message via the registrar. This works especially when
the registrar is fully stateless and shortens the amount of messages
being sent in case of a failover scenario. The idea of resumption of
a registration or a session is working also for other protocols than
SIP e.g., TLS 1.2 [RFC5246] or TLS 1.3 [RFC8446]. AVORS use the idea
of session resumption for SIP via a session data base dip from the
SIP Proxy as an alternative approach to optimize registration
behavior especially in case of heavy outages and registration storms.
The mechanism does not obsolete the original or classical
registration behavior and is complementary. The UE or end devices
can run either in classical or AVORS mode in order to trigger
registration resumption. The SIP core systems can operate in
classical and AVORS mode in parallel. In this case only the UE
supporting the AVORS mode, trigger the registration resumption
feature. The AVORS mode is also working in the case that the
failover SIP Proxy (secondary outbound proxy) uses a different IP
address compared to the primary one. The mechanism can be combined
with TLS resumption in the wireline case. The aim of this document
is to specify how resumption for SIP registration works in
combination with a session data base. The focus of this document is
on the aspect of registrations and recovery time in case of outages
e.g., site outages. A fully session resumption including resumption
of media streams needs to be analyzed in an additional work. This
principle is described above for the geo-redundancy use case and also
works for local redundant instances or in combination.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119].
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3. Rationale of the usage of AVORS mode for SIP sessions
By using the AVORS mode for SIP sessions the overcapacity within the
SIP Core or voice systems can be reduced because the amount of
message flows are reduced when the SIP Proxy is able to resume the
registration directly. The approach fits into the SBA of 3GPP and
the introduction of a session data base in context of 5G. Recovery
time of the system is also optimized and shortened which is
beneficial for the users. In future cloud based SIP applications
will run as virtual instances or in containers and will have a
session data base anyway. Therefore, it is reasonable to provide an
adapted registration or re-registration mechanism when migrating the
SIP systems into the cloud.
Regarding the UE there are two paths possible:
* UE agnostic approach requiring that the voice SIP core applies the
AVORS mode to all register messages. No special indication is
given by the UE that it works in either the classical or the AVORS
mode.
* UE AVORS approach where the UE sends an AVORS header or parameter
indicating that it is working in AVORS mode. Without sending this
AVORS parameter, it is assumed that the UE is working in classical
registration mode and the voice core does not apply the AVORS mode
to the regarding register messages.
Depending on the installed basis of the operator or the operational
requirements both options are valid approaches. In case the UE
indicates that it operates in AVORS mode an AVORS header needs to be
specified.
4. Architecture Overview of AVORS Concept
This section gives an overview of the registration resumption concept
for SIP sessions. As stated above the classical registration
mechanism in case of a failure of a site or a SIP Proxy failure is to
start a new initial registration towards the secondary outbound proxy
and SIP Proxy respectively. The registration process invokes SIP
Proxy, SIP Server and the session data base. With AVORS the SIP
Proxy is able to resume a registration by handling a normal re-
register message of the UE. Instead of starting a new initial
registration the UE sends the normal re-registration message to the
secondary outbound proxy namely SIP Proxy. The SIP Proxy gets the
session registration context out of the data base where the session
context is stored, i.e., session data base. In case of using a TLS
session the session resumption process can be implemented for both
protocols, TLS and SIP, making the recovery and failover process more
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efficient. The spare overcapacity needed for processing the initial
registration process can be reduced and the recovery mechanism is
kept efficient. TCP session resumption is no prerequisite for TLS
session resumption in case a TCP session is used instead of UDP.
The AVORS architecture is described in the following figures.
Figure 1 describes the geo-redundancy use case.
Initial register.
+---------+
+-------+ | |
| | |SIP Proxy|
| DNS | | Site #1 |
| | /| | \
+-------+ / +---------+ \
| / \
| / \
| / sip \
| / initial +---------+
+-------+ / register | Session |
| |/ | Data |
| UE | | Base |
| | | |
+-------+ +---------+
/
+---------+ /
| | /
|SIP Proxy| /
| Site #2 |/
| |
+---------+
Registration resumption in case of a failover to
the secondary outbound proxy or SIP Proxy respectively.
\ /
+---------+
+-------+ | \ / |
| | |SIP Proxy|
| DNS | | Site #1 |
| | | / \ | \
+-------+ +---------+ \
| / \ \
| \
| \
| +---------+
+-------+ | Session |
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| | | Data |
| UE |\ | Base |
| | \ | |
+-------+ \ +---------+
\ /
\ +---------+ /
sip \ | | /
registration\ |SIP Proxy| /
resumption \| Site #2 |/
| |
+---------+
Figure 1: AVORS Geo-Redundancy.
Figure 2 describes the local-redundancy use case.
Initial register.
+---------+
+-------+ | |
| | |SIP Proxy|
| DNS | | Inst.#1 |
| | /| | \
+-------+ / +---------+ \
| / \
| / \
| / sip \
| / initial +---------+
+-------+ / register | Local |
| |/ | Data |
| UE | | Base |
| | | |
+-------+ +---------+
/
+---------+ /
| | /
|SIP Proxy| /
| Inst.#2 |/
| |
+---------+
Registration resumption in case of a failover to
the secondary local SIP Proxy instance.
\ /
+---------+
+-------+ | \ / |
| | |SIP Proxy|
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| DNS | | Inst.#1 |
| | | / \ | \
+-------+ +---------+ \
| / \ \
| \
| \
| +---------+
+-------+ | Local |
| | | Data |
| UE |\ | Base |
| | \ | |
+-------+ \ +---------+
\ /
\ +---------+ /
sip \ | | /
registration\ |SIP Proxy| /
resumption \| Inst.#2 |/
| |
+---------+
Figure 2: AVORS Local-Redundancy.
5. AVORS Procedure for SIP
AVORS (Avoidance of Registration Storms): The following sections
describes the procedures for AVORS which allows a seamless switch
over of UE in case of a faulty connection towards the first SIP proxy
where the UE is connected. When changing the SIP proxy a simple
(Re-) REGISTER is needed to reconnect instead of an challenged
initial registration procedure.
The following SIP option tag shall apply: This amendment specifies a
single option tag, avors. The required information for this
registration, as specified in [RFC3261], is:
Name: avors
Description: This option tag is for the procedure used to send a re-
register instead of a register when changing the first network proxy
due to network failure/proxy failure. To allow this procedure the
network will indicate if this procedure is implemented.
The next part describes a possible process. It is requested to
include the SIP Instance-ID in the Contact-Header. For TCP based
protocols TFO (TCP Fast Open) according to [RFC7413] shall be
supported. Latter is relevant for the SIP Proxy instances. For TLS
based transport protocols TLS session resumption according to
[RFC8446] is used at the failover SIP Proxy instance. Additionally,
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the "avors" option tag in order to query SIP Proxy support for
Registration Recovery Procedure or registration resumption,
respectively, is introduced.
The following procedures shall apply:
1. The UE determines a SIP Proxy instance by a standard SIP Proxy
discovery mechanism.
2. The UE performs an initial SIP registration at the SIP Proxy.
a. In addition, the UE sends an option tag "avors" in the
Supported header field in any SIP register request message.
b. The UE expects an option tag "avors" in the Supported header
field in the 200 OK response to a SIP registration from
the SIP Proxy. If the SIP Proxy supports AVORS, the UE receives
an option tag "avors" in the Supported header field
of the 200 OK.
3. For all cases that require the UE to change to a different
SIP Proxy instance and a registration was successfully
negotiated, the following behavior applies:
Note: For AVORS, a re-register on a new SIP Proxy is
considered as new request in an existing dialog.
Note: The Contact header field may contain no port number
or port number according to {{RFC3261}}.
For UEs supporting AVORS, the Contact header field must not
be changed on a re-register to a new SIP Proxy.
Note: It is requested that the UE supports SIP Instance-ID
and includes it in the Contact header field.
Note: For AVORS, any re-register sent to a new SIP Proxy
MUST also perform re-registration procedures regarding
commitment to nonce, retaining the call-id and increase of
the CSeq by at least the value 1.
a. If TLS was used as a transport protocol:
i. If TCP session used by the TLS transport fails and
the „Timer F“ has not expired, the UE shall not immediately
try to send a Re-register message to the secondary
SIP Proxy until the re-registration timer is expired.
This avoids a mass registration at the secondary
SIP Proxy, the re-registration gets spread over the
UE re-registration time of a defined value of e.g., x min.
ii. In case of a failed TCP session the UE shall attempt
a TLS session resumption according to {{RFC8446}} on the
new SIP Proxy instance using the TLS session data
obtained from the initial handshake on the original
SIP Proxy instance.
The UE shall delete the TLS session data determined
during the initial TLS handshake with the original
SIP Proxy from its internal memory when a new initial
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register for this contact has to be executed or if the
timers belonging to the TLS session have expired
or the TLS resumption failed.
iii.The UE will send a re-register request to the new SIP Proxy
instance instead of an initial register message.
b. If UDP is used between UE and SIP Proxy:
i. If a SIP message is not answered or in case that a
keepalive is failed, the UE will send a re-register
request to the new SIP Proxy instance instead of
a register.
ii. The UE shall not immediately try to send a re-register message
to the secondary SIP Proxy until the Re-registration timer
is expired. This avoids a mass registration at the
secondary SIP Proxy, the re-registration gets spread over the
UE re-registration time of a defined time e.g., x min.
c. If TCP is used between UE and SIP Proxy:
i. If TCP session used with or without TLS fails and
the „Timer F“ has not expired, the UE shall not
immediately trying to send a Re-register message to the
secondary SIP Proxy until the Re-Registration timer is expired.
This avoids a mass registration at the secondary SIP Proxy,
the Re-Registration gets spread over the UE Re-Registration
time of a defined value of x min.
ii. In case of a failed TCP session the UE shall attempt a TCP
session resumption (TCP Fast Open (TFO)) according to
{{RFC7413}} on a new SIP Proxy instance using the TFO session
cookie obtained from the initial handshake on the original
SIP Proxy instance.
iii. The UE shall delete the TFO session cookie determined during
the initial TCP handshake with the original SIP Proxy from its
internal memory when the user de-registers or gets
de-registered by the network or if the timers belonging to
the TFO session cookie have expired or the TCP session
resumption failed.
iv. The UE will send a Re-Register request to the new SIP Proxy
instance instead of an initial Register message.
4. Optional “Re-register on not answered Invite message”
i. If an Invite message to primary SIP Proxy receives no response,
the UE shall send a re-register to secondary SIP Proxy and,
after receiving 200 OK, shall send the Invite message to
secondary SIP Proxy.
Note: Upon receiving a 503 (Service Unavailable) response
to an initial invite request containing a Retry-After header
field, then the originating UE shall not automatically
reattempt the request until after the period
indicated by the Retry-After header field contents.
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5. UE behavior if SIP Proxy doesn’t support AVORS
i. If SIP Proxy doesn’t support option tag "avors" in the
Supported header field in the 200 OK of a
SIP registration, an initial registration
has to be performed when
switching to a new SIP Proxy IP address
(no change to current behavior).
6. Functions of Registration Resumption Feature
This document is focusing on the introduction of registration
resumption in a SIP (Session Initiation Protocol) environment. The
method can be used for SIP-Proxies and SIP-Registrars. It also works
in context of 3GPP SBA (Service Based Architecture) and with a
session data base [TS_29.598]. In a second step, one can consider
using a similar advanced mechanism for complete session resumption.
The procedure and functions described here are part of a stateless
voice architecture and are suitable for use in a cloud environment.
7. Related work
Related work can be found in the referenced standards.
8. Security and operational considerations
Registration or session resumption leads to a situation where
security plays a role to avoid unauthenticated and unauthorized
access to the platform. The security can be hardened in case the sip
session resumption is combined with a TLS session resumption. The
AVORS mechanism helps in special failure situations to increase the
recovery of the platform. It is up to the implementation to request
a new initial registration after a longer time interval. Such kind
of mechanism would increase security. In case of TCP or TLS the IP
address spoofing is not or difficult to achieve. In case of UDP a
nonce and next-nonce mechanism with short re-registration timer
ensures security. This is also valid in case of using AVORS.
Other security considerations will be addressed in future versions of
the document.
9. Abbreviations
+=========+==============================+
| Abbrev. | Description |
+=========+==============================+
| AVORS | Avoiding Registration Storms |
+---------+------------------------------+
| IAD | Integrated Access Device |
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+---------+------------------------------+
| RG | Residential Gateway |
+---------+------------------------------+
| UE | User Equipment |
+---------+------------------------------+
Table 1
10. IANA Considerations
TBD
11. Acknowledgements
This work has been supported by various contributors. Special thanks
to them. TBD
12. References
12.1. Normative References
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, DOI 10.17487/RFC2246, January 1999,
<https://www.rfc-editor.org/info/rfc2246>.
[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>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC6223] Holmberg, C., "Indication of Support for Keep-Alive",
RFC 6223, DOI 10.17487/RFC6223, April 2011,
<https://www.rfc-editor.org/info/rfc6223>.
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<https://www.rfc-editor.org/info/rfc7413>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
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12.2. Informative 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>.
[TS_23.228]
"IP Multimedia Subsystem (IMS); Stage 2", October 2020.
[TS_24.224]
"IP Multimedia Call Control Protocol based on Session
Initiation Protocol (SIP) and Session Description Protocol
(SDP); Stage 3", July 2020.
[TS_29.598]
"Unstructured Data Storage Services; Stage 3", June 2024.
Authors' Addresses
Roland Schott
Deutsche Telekom
Deutsche-Telekom-Allee 9
64295 Darmstadt
Germany
Email: roland.schott@telekom.de
URI: https://www.telekom.de
Michael Kreipl
Deutsche Telekom
Dieselstraße 43
90441 Nuremberg
Germany
Email: michael.kreipl@telekom.de
Bastian Dreyer
Deutsche Telekom
Budapester Straße 18
20359 Hamburg
Germany
Email: Bastian.Dreyer@telekom.de
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Roland Jesske
Deutsche Telekom
Deutsche-Telekom-Allee 9
64295 Darmstadt
Germany
Email: r.jesske@telekom.de
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