Internet Engineering Task Force Gorry Fairhurst Internet Draft University of Aberdeen Document: draft-fairhurst-ipdvb-ule-ext-00.txt Category: Draft June 2006 Extension Formats for the ULE Encapsulation to support the Generic Stream Encapsulation (GSE) Status of this Draft By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes a set of Extension Headers. For the Unidirectional Lightweight Encapsulation (ULE). The Extension Header formats defined in this document provide new extensions that are common extensions to both ULE and the Generic Stream Encapsulation (GSE) defined by the second generation framing structure DVB-S2 standard (Channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications). Expires December 2006 [page 1] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 Expires June 2006 [page 2] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 Table of Contents 1. Introduction 2. Conventions used in this document 3. Description of method 4. Summary 5. IANA Considerations 6. Acknowledgments 7. Security Considerations 8. References 8.1 Normative References 8.2 Informative References 9. Authors' Addresses 10. IPR Notices 10.1 Intellectual Property Statement 10.2 Disclaimer of Validity 11. Copyright Statement 11.1 Intellectual Property Statement 11.2 Disclaimer of Validity Appendix A: Expires June 2006 [page 3] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 1. Introduction This document describes a set of Header Extensions for ULE [RFC4236] over the MPEG-2 Transport-Stream. The methods are also applicable to a link that uses the physical layer specified by DVB-S2 [ETSI-S2] in the Generic Mode (also known as the Generic Stream (GS)). The Generic Stream Encapsulation (GSE) [GSE] is currently a work item of the DVB-TM. The requirements for the Generic Stream are defined in [S2-REQ], [S2-REQ-RCS], and [ID-S2-REQ]. GSE maintains a design philosophy that presents a similar network interface to that of ULE and uses a similar construction for SNDUs. The important characteristics of this encapsulation are described in an Appendix to this document. The approaches seek to define well-founded methods that may be used with both ULE and GSE. This will present the same network layer interface over both physical layers. One method allows one or more TS-Packets [ISO-MPEG] to be sent within a ULE SNDU. In GSE this method may be used to provide then control plane information including the transmission of MPEG-2 Program Specific Information (PSI) for the Multiplex. A second method allows one or more PDUs to be sent within the same ULE SNDU. This method is designed for cases where a large number of small PDUs are directed to the same Network Point of Attachment (NPA) address. The method may improve transmission efficiency (by removing duplicated MAC layer overhead). It can also reduce processing overhead for receivers that are not addressed by the NPA, since these receivers may then skip several PDUs in one operation. The method is defined as a generic extension header and may be used for IPv4 or IPv6 packets. If and when a compression format is defined for ULE or Ethernet, the method may also be used in combination with this method. Future versions of this document are expected to provide recommendations on the interface between the Generic Stream Encapsulation (GSE) and the Internet Protocol Stack. The appendix is also expected to be enhanced to include a summary of key design issues and considerations based on the GSE Specification defined by the DVB-TM (e.g. [ID-S2-REQ]). Expires June 2006 [page 4] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 2. Conventions used in this document 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 RFC 2119 [RFC2119]. b: bit. For example, one byte consists of 8b. B: Byte. Groups of bytes are represented in Internet byte order. BBFrame payload [ETSI-S2]: The data field part of a Baseband frame that may be used for the communication of data. Typical BBFrames range in size from 3072 to 58192 bits according to the choice of modulation format and FEC in use. DVB: Digital Video Broadcast. A framework and set of associated standards published by the European Telecommunications Standards Institute (ETSI) for the transmission of video, audio, and data. Encapsulator: A network device that receives PDUs and formats these into Payload Units (known here as SNDUs) for output in the Generic Mode of DVB-S2. GS: Generic Stream. GSE: Generic Stream Encapsulation. MAC: Medium Access Control [IEEE-802.3]. A link layer protocol defined by the IEEE 802.3 standard (or by Ethernet v2). MPEG-2: A set of standards specified by the Motion Picture Experts Group (MPEG), and standardized by the International Standards Organisation (ISO/IEC 113818-1) [ISO-MPEG], and ITU-T (in H.220). Next-Header: A Type value indicating an Extension Header [RFC4236]. NPA: Network Point of Attachment [RFC4236]. In this document, refers to a destination address (resembling an IEEE MAC address) within the DVB-S2 transmission network that is used to identify individual Receivers or groups of Receivers. PDU: Protocol Data Unit [RFC4259]. Examples of a PDU include Ethernet frames, IPv4 or IPv6 datagrams, and other network packets. PSI: Programme Specific Information [ISO-MPEG]. SI Table: Service Information Table [ISO-MPEG]. In this document, this term describes a table that is been defined by another standards body to convey information about the services carried in a Expires June 2006 [page 5] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 SNDU: Subnetwork Data Unit [RFC4259]. In this document this is an encapsulated PDU sent using GSE. Stream: A logical flow from an Encapsulator to a set of Receivers. The addresses at the MAC/NPA level and IP level need to be unique within a specific stream (i.e. denoted by a common S.2 ISI value). TS: Transport Stream [ISO-MPEG], a method of transmission at the MPEG-2 level using TS Packets; it represents layer 2 of the ISO/OSI reference model. ULE: Unidirectional Lightweight Encapsulation (ULE) [RFC4236]. A scheme that encapsulates PDUs, into SNDUs that are sent in a series of TS Packets using a single TS Logical Channel. The encapsulation format defined by this document shares the same extension format, and basic processing rules and uses a common IANA Registry. Expires June 2006 [page 6] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 3. Description of the Method In ULE, a Type field value less than 1536 Decimal indicates an Extension Header. This section describes a set of two extension formats for the ULE encapsulation. 3.1 MPEG-2 TS-Concat Extension The MPEG-2 TS-Concat Extension Header is specified by an IANA assigned H-Type value of . This is a Mandatory Next-Header Extension. The extension is used to communicate 1 or more MPEG-2 TS Packets within a ULE SNDU. The number of TS Packets carried in a specific SNDU is determined from the size specified by the remainder of the Payload following the MPEG-2 TS Extension. A Receiver MUST silently discard any data, if present, between the last complete encapsulated MPEG-2 TS Packet and the size denoted in the Length field of the SNDU fragment base header. A value of D=1 indicates there is no NPA/MAC address in use. A value D=0 is also permitted, as defined in ULE. The extension may be used to communicate one or more MPEG-2 TS Packets of arbitrary content, interpreted according to [ISO-MPEG]. One expected use is for the transmission of MPEG-2 SI/PSI signalling and clock references over the ULE framing. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Length (15b) | Type = 0xtbd | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TS-Packet 1 | = = | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TS-Packet 2 (if Length > 2*188) | = = | etc. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (CRC-32) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: SNDU Format for a TS-Packet Payload (D=1) Expires June 2006 [page 7] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Length (15b) | Type = 0xtbd-concat | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receiver Destination NPA Address (6B) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | TS-Packet 1 | = = | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TS-Packet 2 (if Length > 2*188) | = = | etc. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (CRC-32) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: SNDU Format for a TS-Packet Payload (D=0) 3.2 PDU-Concat Extension The PDU-Concat Extension is specified by an IANA assigned H-Type value of . This is a Mandatory Next-Header Extension. It enables a sequence of (usually short) PDUs to be sent within a single SNDU payload. The base header contains the Length of the entire SNDU. This is set to the combined length of all PDUs to be encapsulated, including each set of encapsulation headers. Each PDU is prefixed by its length in bytes (shown as PDU-Length in the following diagrams) and a 16-bit ULE Type field. The most significant bit of the first byte MUST must be set to zero. The length of each PDU MUST be less than 32 768 bytes. The Type field (shown as PDU-Type in the following figures) may be any ULE- specified Type. The Receiver processes this Extension Header by extracting each PDU in turn. The Receiver first verifies the Length of each PDU, and ensures the sum of the Lengths of all processed PDUs is less than the Length specified in the SNDU base header. A Receiver MUST silently discard any data, if present, after the last complete encapsulated PDU. Expires June 2006 [page 8] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Length (15b) | Type = 0xtbd-concat | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| PDU-Length (15b) | PDU-Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ = PDU-1 = | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| PDU-Length (15b) | PDU-Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ = PDU-2 = | | More PDUs as required +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (CRC-32) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SNDU Format for a PDU-Concat Payload (D=1) A value of D=1 indicates there is no NPA/MAC address in use. This field MUST be carried (i.e. D=0) for IP unicast packets destined to routers that are sent using shared links (i.e., where the same link connects multiple Receivers). A sender MAY omit this field (D=1) for a set of packets delivered to a Receiver or group of receivers that are able to utilise a discriminator field (e.g. the IPv4/IPv6 destination address, or a bridged MAC destination address), which in combination with the PID value, could be interpreted as a Link-Level address. When the SNDU header indicates the presence of an SNDU Destination Address field (i.e. D=0), a Network Point of Attachment, NPA, field directly follows the fourth byte of the SNDU header. NPA destination addresses are 6 Byte numbers, normally expressed in hexadecimal, used to identify the Receiver(s) in a transmission network that should process a received SNDU. When present the Receiver MUST associate the same specified MAC/NPA address with all PDUs within the SNDU Payload. This MAC/NPA address MUST also be forwarded with each PDU, if required by the forwarding interface. Expires June 2006 [page 9] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Length (15b) | Type = 0xtbd-concat | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receiver Destination NPA Address (6B) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ||0| Length (15b) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Frag-Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | = PDU-1 = | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Length (15b) | Frag-Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ = PDU-2 = | | More PDUs as required +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (CRC-32) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: SNDU Format for a PDU-Concat Payload (D=1) 4. Summary This document defines a set of Next_Header options for the Unidirectional Lightweight Encapsulation (ULE). 5. IANA Considerations This document will require IANA involvement for the assignment of two new Next-Header Type values from the IANA ULE Next-Header Registry. These options are defined for specific use cases envisaged by GSE, but are compatible with ULE. The TS-Concat Extension is a Mandatory next-type extension header, specified in section 3.1 of this document. The value of this next- header is defined by an IANA assigned H-Type value of . The PDU-Concat Extension is a Mandatory next-type extension header specified in section 3.2 of this document. The value of this next- header is defined by an IANA assigned H-Type value of . 6. Acknowledgments The author gratefully acknowledges the inputs, comments and assistance offered by the members of the DVB-GBS ad hoc group on S2 Expires June 2006 [page 10] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 encapsulation, in particular contributions on networking aspects from Axel Jahn, Ulrik De Bie, and Bernhard Collini-Nocker.. 7. Security Considerations No specific security issues are raised within this document. Additional security control fields may be provided as a part of a link encryption Extension Header, e.g. to associate a PFU with one of a set of Security Association (SA) parameters. As a part of the encryption process, it may also be desirable to authenticate some/all of the headers. The method of encryption and the way in which keys are exchanged is beyond the scope of this specification, as also are the definition of the SA format and that of the related encryption keys. 8. References 8.1 Normative References [RFC2119] Bradner, S., "Key Words for Use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, 1997. [RFC4236] Fairhurst, G. and B. Collini-Nocker, "Unidirectional Lightweight Encapsulation (ULE) for transmission of IP datagrams over an MPEG-2 Transport Stream", RFC 4236, December 2006. 8.2 Informative References [ETSI-DAT] EN 301 192, "Specifications for Data Broadcasting", European Telecommunications Standards Institute (ETSI). [ETSI-S2] EN 302 307, "Digital Video Broadcasting (DVB); Second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications", European Telecommunication Standards Institute (ETSI). [GSE] "Generic Stream Encapsulation", Work in Progress, DVB Technical Module (GBS Group), 2006. [ID-S2-REQ] "Requirements for transmission of IP datagrams over DVB- S2", Internet Draft , Work in Progress. [ISO-MPEG] ISO/IEC DIS 13818-1:2000, "Information Technology; Generic Coding of Moving Pictures and Associated Audio Information Systems", International Standards Organisation (ISO). Expires June 2006 [page 11] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 [RFC4259] Montpetit, M.-J., Fairhurst, G., Clausen, H., Collini- Nocker, B., and H. Linder, "A Framework for Transmission of IP Datagrams over MPEG-2 Networks", RFC 4259, November 2006. [S2-Eval] "Procedure for Comparative Evaluation of IP/DVB-S2 Encapsulation Protocol over Generic Streams", Technical Note, Work in Progress, DVB TM-GBS. [S2-REQ] GBS0339, "Functional and performance requirements for IP/S2", DVB-TM GBS WG. [S2-REQ-RCS] "Requirements for S2", Document 529r1, DVB Technical Module (RCS WG). 9. Authors' Addresses Godred Fairhurst Department of Engineering University of Aberdeen Aberdeen, AB24 3UE UK Email: gorry@erg.abdn.ac.uk Web: http://www.erg.abdn.ac.uk/users/Gorry 10. IPR Notices 10.1 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. Expires June 2006 [page 12] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 10.2 Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 11. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. [RFC EDITOR NOTE: This section must be deleted prior to publication] DOCUMENT HISTORY Draft 00 This draft complements a study item in the DVB-GBS in this area to define a Generic Stream Encapsulation (GSE). Comments relating to this document will be gratefully received by the author(s) and may also be sent to ip-dvb mailing list at: ip-dvb@erg.abdn.ac.uk [END of RFC EDITOR NOTE] Expires June 2006 [page 13] INTERNET DRAFT Extension Formats for the ULE Encapsulation Jun 2006 APPENDIX: DVB-S.2 PDUs, (Ethernet Frames, IP datagrams or other network layer packets) are encapsulated to form a Subnetwork Data Unit (SNDU) [RFC4236] associated with a specific Stream at the link layer. The SNDU is transmitted over an DVB-S2 link by placing it either in a single BBFrame, or if required, an SNDU may be fragmented into a series of BBFrames [ID-S2-REQ]. A mode also permits an SNDU to be fragmented with the remaining fragments sent in a later BBFrame(s), while preserving the original order of each SNDU sent to a specific MAC/NPA address over a Stream. Where there is sufficient space, the method permits a BBFrame to carry more than one SNDU (or part there of), sometimes known as Packing. All parts comprising an SNDU are assigned to the same Stream. In ULE and MPE [ETSI-DAT], each SNDU carries a 32-bit CRC field in the last four bytes of the SNDU. The purpose of this CRC is to protect the SNDU (header, and payload) from undetected reassembly errors and errors introduced by unexpected software / hardware operation. This also serves to verify the delineation (framing) of PDUs and may detect the presence of uncorrected errors from the physical link When an SNDU is sent over a DVB-S2 subnetwork using GSE, the Integrity protection is provided by a CRC at the baseband frame level. Expires June 2006 [page 14]