One document matched: draft-ietf-mmusic-kmgmt-ext-08.txt
Differences from draft-ietf-mmusic-kmgmt-ext-07.txt
Internet Engineering Task Force J. Arkko
MMUSIC Working Group E. Carrara
INTERNET-DRAFT F. Lindholm
Expires: February 2004 M. Naslund
K. Norrman
Ericsson
August 2003
Key Management Extensions for Session Description
Protocol (SDP) and Real Time Streaming Protocol (RTSP)
<draft-ietf-mmusic-kmgmt-ext-08.txt>
Status of this memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines general extensions for SDP and RTSP to carry
the security information needed by a key management protocol, in
order to secure the media. These extensions are presented as a
framework, to be used by one or more key management protocols. As
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such, its use is meaningful only when it is completed by the key
management protocol in use.
General guidelines are also given on how the framework should be used
together with SIP and RTSP.
TABLE OF CONTENTS
1. Introduction.....................................................2
1.1. Notational Conventions.........................................3
2. Extensions to SDP and RTSP.......................................4
2.1. SDP Extensions.................................................4
2.2. RTSP Extensions................................................4
3. Usage with SIP and RTSP..........................................5
3.1. General SDP processing.........................................5
3.2. SIP usage......................................................7
3.3. RTSP usage.....................................................8
3.4. Example scenarios..............................................9
4. Adding further Key management protocols.........................11
5. Security Considerations.........................................12
6. IANA Considerations.............................................13
6.1. SDP Attribute Registration....................................13
6.2. Protocol Identifier Registration..............................13
8. Acknowledgments.................................................14
9. Author's Addresses..............................................14
10. References.....................................................15
10.1. Normative References.........................................15
10.2. Informative References.......................................15
1. Introduction
[Editor remark] All instances of RFC xxxx should be replaced with
the RFC number of this document, when published. Furthermore, all
instances of RFC yyyy should be replaced with the RFC number of
the MIKEY (Multimedia Internet KEYing) document [MIKEY], when
published.
There has recently been work to define a security framework for the
protection of real-time applications running over RTP, [SRTP].
However, a security protocol needs a key management infrastructure to
exchange keys and security parameters, manage and refresh keys, etc.
A key management protocol is executed prior to the security protocol
execution. The key management protocol's main goal is to, in a secure
and reliable way, establish a security association for the security
protocol. This includes one or more cryptographic keys and the set of
necessary parameters for the security protocol, e.g., cipher and
authentication algorithm to be used. The key management protocol has
similarities with, e.g., SIP [SIP] and RTSP [RTSP] in the sense that
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it negotiates necessary information in order to be able to setup the
session.
The focus in the following sections is to describe a new SDP
attribute and RTSP header extension to support key management, and
the integration within SIP and RTSP. A framework is therefore
described in the following. This framework is completed by one or
more key management protocols, to describe how the framework is used,
e.g. which is the data to be carried in the extensions.
Some of the motivations to create a framework with the possibility to
include the key management in the session establishment are:
* Just as the codec information is a description of how to encode and
decode the audio (or video) stream, the key management data is a
description of how to encrypt and decrypt the data.
* The possibility to negotiate the security for the entire multimedia
session at the same time.
* The knowledge of the media at the session establishment makes it
easy to tie the key management to the multimedia sessions.
* This approach may be more efficient than setting up the security
later, as that approach might force extra roundtrips, possibly
also a separate set-up for each stream, hence implying more delay
to the actual setup of the media session.
* The possibility to negotiate keying material end-to-end without
applying end-to-end protection of the SDP (instead, hop-by-hop
security mechanisms can be used which may be useful if
intermediate proxies needs access to the SDP).
Currently in SDP [SDPnew], one field exists to transport keys, i.e.
the "k=" field. However, this is not enough for a key management
protocol as there are many more parameters that need to be
transported. The approach here is to use and extend the SDP
description to transport the key management offer/answer and also to
associate it with the media sessions. SIP uses the offer/answer model
[OAM] whereby extensions to SDP will be enough. However, RTSP
[RTSP]does not use the offer/answer model with SDP, so a new header
is introduced to convey key management data.
1.1. Notational Conventions
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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2. Extensions to SDP and RTSP
This section describes common attributes that are to be included in
an SDP description or in an RTSP header when an integrated key
management protocol is used. The attribute values MUST follow the
general SDP or RTSP guidelines (see [SDPnew] and [RTSP]).
For both SDP and RTSP, the general method of adding the key
management protocol is to introduce new attributes, one identifier to
identify the specific key management protocol, and one data field
where the key management protocol data is placed. The key management
protocol data contains the necessary information to establish the
security protocol, e.g., keys and cryptographic parameters. All
parameters and keys are protected by the key management.
2.1. SDP Extensions
This section provides an Augmented Backus-Naur Form (ABNF) grammar
(as used in [SDPnew]) for the key management extensions to SDP.
Note that the new definitions are compliant with the definition of an
attribute field, i.e.
attribute = (att-field ":" att-value) | att-field
One new attribute for SDP is defined:
key-mgmt = "key-mgmt: " prtcl-id keymgmt-data
prtcl-id = non-ws-string
; e.g. "mikey"
keymgmt-data = text
where non-ws-string and text are as defined in SDP [SDPnew]. The
attribute may be used at session level, media level, or at both
levels. An attribute defined at media level overrides an attribute
defined at session level. Note that the prtcl-id name will be case
sensitive and it is therefore RECOMMENDED that attributes registered
are in lower case letters. Section 3 describes in detail how the
attributes are used and how the SDP is handled in different usage
scenarios.
2.2. RTSP Extensions
To support the needed attribute, the following RTSP header is
defined:
KeyMgmt = "keymgmt" ":" 1#key-mgmt-spec
key-mgmt-spec = "prot" "=" token ";" "data" "=" quoted-string
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"token" and "quoted-string" are as defined in the RTSP specification
[RTSP].
The KeyMgmt header should be possible to use in the messages
described in the table below.
Method Direction Requirement
DESCRIBE C->S required
SETUP C->S required
ANNOUNCE C->S, S->C optional (required: if re-key is supported)
Note: Section 3 describes in detail how the RTSP extensions are used.
3. Usage with SIP and RTSP
This section gives recommendations of how/when to include the defined
key management attribute when SIP and/or RTSP are used together with
SDP.
When a key management protocol is integrated with SIP/SDP and RTSP,
the following requirements are placed on the key management:
* It MUST be possible to execute the key management protocol in at
most one roundtrip in case the answerer accepts the offer.
* It MUST be possible from the SIP/SDP and RTSP application, using
the key management API, to receive key management data, and
information of whether a message is accepted or not.
Today, the MIKEY protocol [MIKEY] has adopted the key management
extensions to work together with SIP and RTSP. Other protocols MAY
use the described attribute and header, e.g. Kerberos [KERB].
3.1. General SDP processing
When an SDP message is created, the following procedure should be
applied:
* The identifier of the key management protocol used (e.g. MIKEY or
Kerberos) MUST be placed in the prtcl-id field.
* The keymgmt-data field MUST be created as follows. The key
management protocol MUST be used to create the key management
message. This message SHALL be base64 encoded [RFC3548] by the SDP
application and then encapsulated in the keymgmt-data attribute.
The data may e.g. be a MIKEY message (see [MIKEY], Section 7) or
Kerberos ticket.
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A received SDP message that contains the key management attributes
SHOULD be processed in the following manner:
* The key management protocol is identified according to the prtcl-id
field.
* The key management data from the keymgmt-data field MUST be
extracted, base64 decoded to reconstruct the original message, and
then passed to the key management protocol. Note that depending on
key management protocol, some extra parameters might of course be
requested by the specific API, such as the source/destination
network address/port(s) for the specified media (however, this
will be implementation specific depending on the actual API).
* Depending on the outcome of the key management processing (i.e.
whether it was successful or not), the processing can proceed
according to normal rules (e.g. according to the offer/answer
model, see also Section 3.2).
Note that the key management attribute MAY be repeated more than once
(e.g., one at session level and one at media level). Consequently,
the process is repeated for each key management attribute detected.
However, in case of failure of the key management (on either session
or media level), the session setup SHALL be aborted (see also Section
3.2 and Section 3.3 for more details).
If more than one key management protocol is supported, multiple
instances of the key management attribute MAY be included in the
initial offer, each transporting a different key management data,
thus indicating supported alternatives.
If the sender includes more than one key management protocol
attribute at session level (analogous for the media level), these
SHOULD be listed in order of preference (the first being the
preferred). The receiver selects the key management protocol it
wishes to use and includes only that attribute in the answer. If the
receiver does not support any of the sender's suggested key
management protocols, the receiver returns an error message (see
section 3.2 and section 3.3), whereby the sender MUST abort the
current setup procedure.
Note that the placement of multiple key management offers in a single
message has the disadvantage that the message expands and the
computational workload for the offerer will increase drastically.
The possibility to support multiple key management protocols may
introduce bidding down attacks. To avoid this, the list of
identifiers of the proposed key management protocols MUST be
authenticated. The authentication MUST be done separately by each key
management protocol (see e.g. Section 7.1 in [MIKEY]).
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Accordingly, it MUST be specified (in the key management protocol
specification itself or in a companion document) how the list of key
management protocol identifiers can be authenticated from the offerer
to the answerer by the specific key management protocol. Note that
even if only one key management protocol is used, that still MUST
authenticate its own protocol identifier.
The list of protocol identifiers MUST be given to the selected key
management protocol by the SDP application with ";" separated
identifiers. All the offered protocol identifiers MUST be included,
in the same order as they appear in the corresponding SDP
description.
The protocol list can formally be described as
prtcl-list = prtcl-id *(";" prtcl-id)
prtcl-id = non-ws-string
For example, if the SDP is:
v=0
o=alice 2891092738 2891092738 IN IP4 lost.example.com
s=Secret discussion
t=0 0
c=IN IP4 lost.example.com
a=key-mgmt:mikey <data1>
a=key-mgmt:keyp1 <data2>
a=key-mgmt:keyp2 <data3>
m=audio 39000 RTP/SAVP 98
a=rtpmap:98 AMR/8000
m=video 42000 RTP/SAVP 31
a=rtpmap:31 H261/90000
The protocol list, "mikey;keyp1;keyp2", would be generated from
the SDP description and used as input to each specified key
management protocol (together with the data for that protocol).
If more than one protocol is supported by the offerer, it is
RECOMMENDED that all acceptable protocols are included in the first
offer, rather than making single, subsequent alternative offers in
response to error messages, see "Security Considerations".
3.2. SIP usage
When used with SIP and the offer/answer model, the offerer SHOULD
include the key management data within an offer that contains the
media description it should apply to. The answerer MUST check with
the key management protocol if the attribute values are valid, and
then obtain from the key management the data to include in the
answer.
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If the offer is not accepted, the answerer SHOULD return a "606 Not
Acceptable" message, including one or more Warning headers (at least
a 306 "Attribute not understood"). The session is then aborted (and
it is up to local policy or end user to decide how to continue).
Re-keying can be handled as a new offer, i.e. a re-INVITE should be
sent with the new proposed parameters. The answerer treats this as a
new offer where the key management is the issue of change. In
general, the re-INVITE (and the key exchange) must be finalized
before the security protocol can change the keys. The same key
management protocol used in the original INVITE SHALL also be used in
the re-INVITE carrying re-keying. If the re-INVITE carrying re-keying
fails (e.g., the authentication verification fails), the answerer
SHOULD send a "606 Not Acceptable" message, including one or more
Warning headers (at least a 306). The offer MUST then abort the
security setup.
3.3. RTSP usage
RTSP does not use the offer/answer model, as SIP does. This causes
some problems, as it is not possible (without abusing RTSP) to send
back an answer to the server (as the server will in most cases be the
one initiating the security parameter exchange). To solve this, a new
header has been introduced (Section 2.2). This also assumes that the
key management also has some kind of binding to the media, so that
the response to the server will be processed as required.
The initial key management message from a server should be sent to
the client using SDP. When responding to this, the client uses the
new RTSP header to send back an answer (included in the SETUP
message). If a server receives a SETUP message in which it expects a
key management message, but none is included, a 403 Forbidden SHOULD
be returned to the client, whereby the current setup MUST be aborted.
The processing of creating a key management header in RTSP SHOULD be
as follow:
* The identifier of the key management protocol used (e.g. MIKEY or
Kerberos) MUST be placed in the "prot" field of the header.
* The keymgmt-data field MUST be created as follows. The key
management protocol MUST be used to create the key management
message. This message SHALL be base64 encoded by the SDP
application and then encapsulated in the "data" field of the
header. The data may e.g. be a MIKEY message (see [MIKEY], Section
7) or Kerberos ticket.
A received key management header SHOULD be processed in the following
manner:
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* The key management protocol is identified according to the "prot"
field.
* The key management data from the "data" field MUST be extracted,
base64 decoded to reconstruct the original message, and then
passed to the key management protocol. Note that depending on the
key management protocol, some extra parameters might of course be
requested by the specific API, such as the source/destination
network address/port(s) for the specified media (however, this
will be implementation specific depending on the actual API).
* Depending on the outcome of the key management processing (i.e.
whether it was successful or not), the processing can proceed
according to normal rules (see also below).
The server MAY provide re-keying/updating facilities by sending a new
key management message in an ANNOUNCE messages. The ANNOUNCE message
contains an SDP message including the key management parameters. The
response message is put in the new RTSP header in the response from
the client to the server. Note that the ANNOUNCE messages MUST be
supported if this feature is to be used.
3.4. Example scenarios
Example 1 (SIP)
A SIP call is taking place between Alice and Bob. Alice sends an
Invite message consisting of the following offer:
v=0
o=alice 2891092738 2891092738 IN IP4 w-land.example.com
s=Cool stuff
e=alice@w-land.example.com
t=0 0
c=IN IP4 w-land.example.com
a=key-mgmt:mikey uiSDF9sdhs727ghsd/dhsoKkdOokdo7eWsnDSJD...
m=audio 49000 RTP/SAVP 98
a=rtpmap:98 AMR/8000
m=video 52230 RTP/SAVP 31
a=rtpmap:31 H261/90000
i.e. Alice proposes to set up one audio stream and one video stream
that run over SRTP. To set up the security parameters for SRTP, she
uses MIKEY. Note that MIKEY is negotiating the crypto suite for both
streams (as it is placed at the session level).
Bob accepts the offer and sends an answer back to Alice:
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v=0
o=bob 2891092897 2891092897 IN IP4 foo.example.com
s=Cool stuff
e=bob@foo.example.com
t=0 0
c=IN IP4 foo.example.com
a=key-mgmt:mikey skaoqDeMkdwRW278HjKVB...
m=audio 49030 RTP/SAVP 98
a=rtpmap:98 AMR/8000
m=video 52230 RTP/SAVP 31
a=rtpmap:31 H261/90000
Example 2 (SDP)
This example shows how Alice would have done if she wished to protect
only the audio stream.
v=0
o=alice 2891092738 2891092738 IN IP4 w-land.example.com
s=Cool stuff
e=alice@w-land.example.com
t=0 0
c=IN IP4 w-land.example.com
m=audio 49000 RTP/SAVP 98
a=rtpmap:98 AMR/8000
a=key-mgmt:mikey uiSDF9sdhs727ghsd/dhsoKkdOokdo7eWsnDSJD...
m=video 52230 RTP/AVP 31
a=rtpmap:31 H261/90000
Note that even if the key management attribute were specified at
session level, the video part would not be affected by this (as a
security profile is not used).
Example 3 (RTSP)
A client wants to set up a streaming session and requests a media
description from the streaming server.
DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0
CSeq: 312
Accept: application/sdp
From: user@example.com
The server sends back an OK message including an SDP description.
RTSP/1.0 200 OK
CSeq: 312
Date: 23 Jan 1997 15:35:06 GMT
Content-Type: application/sdp
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v=0
o=actionmovie 2891092738 2891092738 IN IP4 movie.example.com
s=Action Movie
e=action@movie.example.com
t=0 0
c=IN IP4 movie.example.com
a=key-mgmt:mikey uiSDF9sdhs727ghsd/dhsoKkdOokdo7eWsnDSJD...
m=audio 0 RTP/SAVP 98
a=rtpmap:98 AMR/8000
control:rtsp://movie.example.com/action/audio
m=video 0 RTP/SAVP 31
a=rtpmap:31 H261/90000
control:rtsp://movie.example.com/action/video
The client is now ready to setup the sessions. It includes the key
management data in the first message going back to the server (i.e.
the SETUP message).
SETUP rtsp://movie.example.com/action/audio RTSP/1.0
CSeq: 313
Transport: RTP/SAVP/UDP;unicast;client_port=3056-3057
keymgmt: prot=mikey; data="skaoqDeMkdwRW278HjKVB..."
The server processes the request including checking the validity of
the key management header.
RTSP/1.0 200 OK
CSeq: 313
Session: 12345678
Transport: RTP/SAVP/UDP;unicast;client_port=3056-3057;
server_port=5000-5001
The RTSP then proceeds as usual (with e.g. a SETUP message for the
video followed by a PLAY message).
4. Adding further Key management protocols
This framework cannot be used with all key management protocols. The
key management protocol needs to comply with the requirements
described in Section 3. To be able to use a key management protocol
with this framework, the following MUST be specified:
* the key management protocol identifier that should be used in the
protocol identifier fields in both SDP and RTSP (e.g. "mikey" for
MIKEY).
* the information the key management needs from SDP and RTSP (Section
3 gives a guideline of what SDP and RTSP needs from the key
management). The exact API is implementation specific, but it
SHOULD at least support to exchange the specified information.
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Note that in particular, the key management MUST always be given
the protocol identifier(s) of the key management protocol(s)
included in the offer in the correct order as they appear.
The key management data MUST be base64 encoded in the SDP and RTSP
fields. Therefore, considerations of possible conversion from the
normal key management representation to base64 SHOULD be taken into
account.
5. Security Considerations
The nature of this document is to allow SDP and RTSP to support
negotiation of the security of the media sessions. It is therefore
not a primary intention of this document to describe possible
security solutions or to define possible security problems. The
defined SDP and RTSP extensions are not believed to introduce any new
security risks to SDP and RTSP, if used as specified.
Note that the purpose of the key management fields is to provide
information to secure the media streams. Under the assumption that
the key management schemes are secure, the SDP can be passed along
unprotected without affecting the key management, and the media
streams will still be secure even if some attackers gained knowledge
of the SDP contents.
However, if the SDP messages are not sent authenticated between the
parties, it is possible for an active attacker to change attributes
without being detected. As the key management protocol may
(indirectly) rely on some of the session information from SDP (e.g.,
address information), an attack on SDP may have indirect consequences
on the key management. Even if the key management protocol does not
rely on parameters of SDP and will not be affected by manipulation of
these, different DoS attacks aimed at SDP (e.g. the SIMCAP
extensions) may lead to undesired interruption in the setup.
In general, it is therefore a good thing, not only to try to secure
the session, but also to secure the session setup. However, the
security of the session setup might not possible on an end-to-end
basis, but may require to be protected on a hop-by-hop basis (this is
generally the case for SIP/SDP when intermediate proxies needs to
obtain information about the sessions etc). In fact, the focus of
this framework is mainly when end-to-end protection of the session
setup is not used, but where the media streams needs to be end-to-end
protected.
Note that it is impossible to assure the authenticity of a declined
offer, since even if it comes from the true respondent, the fact that
the answerer declines the offer usually means that he does not
support the protocol(s) offered, and consequently cannot be expected
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to authenticate the response either. This means that if the initiator
is unsure of which protocol(s) the responder supports, we RECOMMEND
that the initiator offers all acceptable protocols in a single offer.
If not, this opens up the possibility for a "man-in-the-middle"
(MITM) to affect the outcome of the eventually agreed upon protocol,
by faking unauthenticated error messages until the initiator
eventually offers a protocol "to the liking" of the MITM. This is not
really a security problem, but rather a mild form of denial of
service that can be avoided by following the above recommendation.
6. IANA Considerations
6.1. SDP Attribute Registration
A new SDP attribute needs to be registered for the purpose of key
management protocol integration with SDP.
Contact: Fredrik Lindholm
mailto: fredrik.lindholm@ericsson.com
tel: +46 8 58531705
SDP Attribute ("att-field"):
Name: key-mgmt
Long form: key management protocol
Type of name: att-field
Type of attribute: Media and session level
Purpose: See RFC xxxx, Section 2.
Reference: RFC xxxx, Section 2.1
Values: See registrations below
6.2. Protocol Identifier Registration
This document defines one new name space associated with the above
registered key-mgmt attribute i.e., the protocol identifier (see also
Section 2.1 and Section 2.2).
A new registry needs to be set up for "prtcl-id" parameter of the
"key-mgmt" attribute, with the following registration created
initially: "mikey".
Contact: Fredrik Lindholm
mailto: fredrik.lindholm@ericsson.com
tel: +46 8 58531705
Value name: mikey
Long name: Multimedia Internet KEYing
Purpose: Usage of MIKEY with the key-mgmt attribute
Reference: Section 7 in RFC yyyy
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Further entries may be registered according to the "Specification
Required" policy as defined in [RFC2434]. Each new registration needs
to indicate the parameter name and the syntax of possible additional
arguments. Note that the parameter name is case sensitive and it is
recommended that the name should be in lower case letters. For each
new registration, it is mandatory that a permanent, stable, and
publicly accessible document exists that specifies the semantics of
the registered parameter, the syntax and semantics of its parameters
as well as all the requested details of interaction between the key
management protocol and SDP, as specified in this document.
8. Acknowledgments
Thanks to: Rolf Blom, Magnus Westerlund, and the rest involved in the
MMUSIC WG and the MSEC WG.
A special thanks to Joerg Ott and Colin Perkins.
9. Author's Addresses
Jari Arkko
Ericsson
02420 Jorvas Phone: +358 40 5079256
Finland Email: jari.arkko@ericsson.com
Elisabetta Carrara
Ericsson Research
SE-16480 Stockholm Phone: +46 8 50877040
Sweden EMail: elisabetta.carrara@ericsson.com
Fredrik Lindholm
Ericsson Research
SE-16480 Stockholm Phone: +46 8 58531705
Sweden EMail: fredrik.lindholm@ericsson.com
Mats Naslund
Ericsson Research
SE-16480 Stockholm Phone: +46 8 58533739
Sweden EMail: mats.naslund@ericsson.com
Karl Norrman
Ericsson Research
SE-16480 Stockholm Phone: +46 8 4044502
Sweden EMail: karl.norrman@ericsson.com
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10. References
10.1. Normative References
[OAM] Rosenberg, J. and Schulzrinne, H., "An Offer/Answer Model with
the Session Description Protocol (SDP)", IETF, RFC 3264.
[RTSP] Schulzrinne, H., Rao, A., and Lanphier, R., "Real Time
Streaming Protocol (RTSP)", IETF, RFC 2326.
[RFC2119] Bradner, S. "Key words for use in RFCs to Indicate
Requirement Levels", IETF, RFC 2119.
[SDPnew] Handley, M., Jacobson, V., and Perkins, C., "SDP: Session
Description Protocol", Internet Draft, IETF, Work in progress
(MMUSIC), draft-ietf-mmusic-sdp-new-13.txt.
[SIP] Handley, M., Schulzrinne, H., Schooler, E., and Rosenberg, J.,
"SIP: Session Initiation Protocol", IETF, RFC 3261.
[RFC2434] Narten, T. and Alvestrand, H., "Guidelines for Writing an
IANA Considerations Section in RFCs", IETF, RFC 2434.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", IETF, RFC 3548.
10.2. Informative References
[KERB] Kohl, J., Neuman, C., "The Kerberos Network Authentication
Service (V5)", IETF, RFC 1510.
[MIKEY] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and
Norrman, K., "MIKEY: Multimedia Internet KEYing", IETF, RFC yyyy,
[Internet Draft, Work in progress (MSEC)].
[SRTP] Baugher, M., Blom, R., Carrara, E., McGrew, D., Naslund, M,
Norrman, K., and Oran, D., "The Secure Real Time Transport Protocol",
Internet Draft, IETF, Work in Progress (AVT).
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
Arkko, et al. [Page 15]
INTERNET-DRAFT mmusic-kmgmt-ext-08 August 2003
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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This Internet-Draft expires in February 2004.
Arkko, et al. [Page 16]
| PAFTECH AB 2003-2026 | 2026-04-22 15:11:33 |