+++ /dev/null
-.pl 10.0i
-.po 0
-.ll 7.2i
-.lt 7.2i
-.nr LL 7.2i
-.nr LT 7.2i
-.ds LF Riikonen
-.ds RF FORMFEED[Page %]
-.ds CF
-.ds LH Internet Draft
-.ds RH 15 May 2002
-.ds CH
-.na
-.hy 0
-.in 0
-.nf
-Network Working Group P. Riikonen
-Internet-Draft
-draft-riikonen-flags-payloads-00.txt 15 May 2002
-Expires: 15 November 2002
-
-.in 3
-
-.ce 2
-SILC Message Flag Payloads
-<draft-riikonen-flags-payloads-00.txt>
-
-.ti 0
-Status of this Memo
-
-This document is an Internet-Draft and is in full conformance with
-all provisions of Section 10 of RFC 2026. Internet-Drafts are
-working documents of the Internet Engineering Task Force (IETF), its
-areas, and its working groups. Note that other groups may also
-distribute working documents as Internet-Drafts.
-
-Internet-Drafts are draft documents valid for a maximum of six months
-and may be updated, replaced, or obsoleted by other documents at any
-time. It is inappropriate to use Internet-Drafts as reference
-material or to cite them other than as "work in progress."
-
-The list of current Internet-Drafts can be accessed at
-http://www.ietf.org/ietf/1id-abstracts.txt
-
-The list of Internet-Draft Shadow Directories can be accessed at
-http://www.ietf.org/shadow.html
-
-The distribution of this memo is unlimited.
-
-
-.ti 0
-Abstract
-
-This memo describes the data payloads associated with the SILC Message
-Flags, as defined in the SILC Packet Protocol Internet Draft [SILC2]. The
-purpose of the Message Flags is to augment the function of the Private
-Message Payload and Channel Message Payload by allowing the sender to
-tell the receiver what type of data the payload includes, and how the
-data should be processed. Some of the Message Flags may define additional
-payloads to be associated with the flag, and this memo describes these
-payloads.
-
-
-
-
-
-
-
-
-.ti 0
-Table of Contents
-
-.nf
-1 Introduction .................................................. 2
- 1.1 Requirements Terminology .................................. 2
-2 SILC Message Flags ............................................ 2
-3 SILC Message Flag Payloads .................................... 3
- 3.1 SILC_MESSAGE_FLAG_REQUEST ................................. 3
- 3.2 SILC_MESSAGE_FLAG_REPLY ................................... 3
- 3.3 SILC_MESSAGE_FLAG_SIGNED .................................. 4
- 3.4 SILC_MESSAGE_FLAG_DATA .................................... 4
-4 Security Considerations ....................................... 5
-5 References .................................................... 5
-6 Author's Address .............................................. 6
-
-
-.ti 0
-1. Introduction
-
-The Secure Internet Live Conferencing [SILC1] supports sending binary
-messages between users in the network. To make the data sending, and
-processing at the receiver's end as simple as possible the SILC defines
-Message Flags to the Private Message Payload and Channel Message Payload
-[SILC2], which can help the receiver to decide how the data is encoded,
-and how it should be interpreted. Some of the Message Flags may define
-additional payloads to be associated with the flag, but the [SILC2] does
-not define them. This memo defines the payloads for those Message Flags
-that was marked to include additional payloads in [SILC2].
-
-By defining the payloads for the Message Flags the SILC message payloads
-can be augmented to support any kind of data, which can be easily
-interpreted at the receiver end. For example, it would be possible to
-send audio stream, video stream, image files and HTML pages as messages,
-and the receiver can either choose to ignore the message or to process
-it, or to perhaps pass the message to some application for processing.
-Without specific payloads for Message Flags it is almost impossible for
-the receiver to interpret binary data from the payload.
-
-
-.ti 0
-1.1 Requirements Terminology
-
-The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
-MAY, and OPTIONAL, when they appear in this document, are to be
-interpreted as described in [RFC2119].
-
-
-.ti 0
-2 SILC Message Flags
-
-The Message Flags was added to the SILC protocol for the reason that SILC
-provides sending binary data as messages between users, and entities in
-the network, and interpreting pure binary data is almost impossible.
-With the flags the purpose, the reason, and the way the message is
-supposed to be interpreted can be told to the recipient. Other
-conferencing protocols which are usually ASCII based protocols do not have
-such problems since they do not generally support sending of binary data
-at all, or require encoding of the data before it can be sent over the
-network.
-
-SILC Private Message Payload and Channel Message Payload can have flags
-that can augment the function of the payload. The flags can tell for
-example that the message is a request, or a reply to an earlier received
-request. They can tell that the message is some action that the sender
-is performing, or they can tell that the message is an auto reply, or
-that it is explicitly digitally signed by the sender.
-
-The problem of Message Flags is that the space for flags mask is only 16
-bits, so there is a limited number of flags available. For this reason a
-flag that defines some generic way of sending any kind of data as a
-message, and that it can be easily interpreted at the receiver's end is
-important. For this reason the flag SILC_MESSAGE_FLAG_DATA was added to
-the protocol which can represent any data. This memo describe how this
-flag is used and how the associated payload is constructed and processed.
-This memo also describes payloads for all the other flags that can have
-associated payloads.
-
-
-.ti 0
-3 SILC Message Flag Payloads
-
-The [SILC2] defines the flags which may have associated payloads. This
-section will list these flags and define the payloads.
-
-
-.ti 0
-3.1 SILC_MESSAGE_FLAG_REQUEST
-
-Currently this flag can be used in the context of application specific,
-service specific or vendor specific requests, and the data payload type is
-dependent of this context. Therefore, payload is not defined for this
-flag in this memo. This flag may also be masked with some other flag in
-the message payload, including with some other flag that defines
-additional payload.
-
-
-.ti 0
-3.2 SILC_MESSAGE_FLAG_REPLY
-
-Currently this flag can be used in the context of application specific,
-service specific or vendor specific replies, and the data payload type is
-dependent of this context. Therefore, payload is not defined for this
-flag in this memo. This flag may also be masked with some other flag in
-the message payload, including with some other flag that defines
-additional payload.
-
-
-.ti 0
-3.3 SILC_MESSAGE_FLAG_SIGNED
-
-Not defined yet.
-
-
-.ti 0
-3.4 SILC_MESSAGE_FLAG_DATA
-
-This flag is used to represent any data as a message in the way that it
-can be easily interpreted by the recipient. This flag is used to send
-MIME objects as messages from the sender to the receiver. The MIME as
-defined in [RFC2045], [RFC2046], [RFC2047], [RFC2048] and [RFC2049] is
-well established protocol for sending different kind of data with many
-applications and protocols. It support dozens of different media types
-and encodings, and for this reason is ideal for sending data in SILC
-message payloads as well.
-
-When the receiver has checked that the message payload includes the
-SILC_MESSAGE_FLAG_DATA flag, it may then start parsing the MIME header.
-It would also be possible to pass the message to some application which
-can already interpret MIME objects. If the receiver does not support the
-media type received in the MIME header, it SHOULD be treated as
-"application/octet-stream". The receiver MAY also ignore and discard
-messages that it does not support.
-
-The MIME header MUST be at the start of the data area of the Private
-Message Payload or Channel Message Payload. The MIME header received in
-the data area of the payload SHOULD have the MIME-Version field at first
-and then Content-Type field. The MIME-Version field is not required to be
-present in each body part of multipart entity. Additionally the header
-MAY also include any other MIME compliant headers. The character encoding
-for the MIME Header strings inside the message payload is US-ASCII, as
-defined in [RFC2045]. The actual MIME object may define additional
-character sets or encodings for the data it delivers.
-
-Hence, the MIME Header in the message payload may be as follows:
-
-.in 8
-.nf
-MIME-Version: 1.0\\r\\n
-Content-Type: discrete/composite\\r\\n
-Content-Transfer-Encoding: binary\\r\\n
-\\r\\n
-.in 3
-
-The Content-Transfer-Encoding field behaves as defined in [RFC2045] and
-defines the encoding of the data in the MIME object. The preferred data
-encoding with SILC is "binary". However, many MIME media types defines
-their preferred encoding and they may be used if binary encoding is not
-suitable.
-
-When sending large amounts of traffic or large files as MIME objects the
-limits of the SILC Packet needs to be taken into consideration. The
-maximum length of SILC Packet is 2^16 bytes, and larger messages would
-need to be fragmented. MIME provides way of fragmenting and reassembling
-messages, and it is to be done with SILC as defined in [RFC2046]. The
-MIME fragmentation is defined for gateway usage, but in case of SILC the
-sender may also start sending fragmented MIME objects.
-
-This flag SHOULD NOT be masked with some other Message Flag that defines
-payloads. Generally this sort of setting would be impossible for the
-receiver to interpret. However, flags that does not define any specific
-payloads MAY be masked with this flag as well. For example, this flag
-could be masked also with SILC_MESSAGE_FLAG_REQUEST flag.
-
-
-.ti 0
-4 Security Considerations
-
-In case of SILC_MESSAGE_FLAG_DATA the implementors should pay special
-attention to the security implications of any media type that can cause
-the remote execution of any actions in the receiver's environment. The
-[RFC2046] and [RFC2048] discusses more MIME specific security
-considerations. Even though SILC provides secured messages, in case of
-MIME which can be used to transfer files and documents which are stored in
-the receiver's local environment, securing separately the MIME object may
-be desired. For example, augmenting the MIME support in SILC messages to
-support S/MIME may be desired in some implementations.
-
-
-
-.ti 0
-5 References
-
-[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
- Protocol Specification", Internet Draft, May 2002.
-
-[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
- May 2002.
-
-[RFC2045] Freed, N., et al., "Multipurpose Internet Mail Extensions
- (MIME) Part One: Format of Internet Message Bodies",
- Standards Track, RFC 2045, November 1996.
-
-[RFC2046] Freed, N., et al., "Multipurpose Internet Mail Extensions
- (MIME) Part Two: Media Types", Standards Track, RFC 2045,
- November 1996.
-
-[RFC2047] Moore K., "MIME (Multipurpose Internet Mail Extensions)
- Part Three: Message Header Extensions for Non-ASCII Text"
- Standards Track, RFC 2047, November 1996.
-
-[RFC2048] Freed, N., et al., "Multipurpose Internet Mail Extensions
- (MIME) Part Four: Registration Procedures", Standards
- Track, RFC 2048, November 1996.
-
-[RFC2049] Freed, N., et al., "Multipurpose Internet Mail Extensions
- (MIME) Part Five: Conformance Criteria and Examples",
- Standards Track, RFC 2049, November 1996.
-
-[RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
-
-
-.ti 0
-6 Author's Address
-
-Pekka Riikonen
-Snellmaninkatu 34 A 15
-70100 Kuopio
-Finland
-
-EMail: priikone@iki.fi
-
-This Internet-Draft expires 15 November 2002
projects / runtime.git / blobdiff