The UPSTREAMS Protocol for HFC Networks

Transcription

1 matmos::fm:protocol UPSTREAMS book:title The UPSTREAMS Protocol for HFC Networks Mark Laubach, Editor Inc. 750 Tasman Drive Milpitas, CA Voice: FAX: Revision History Standards Version Version Date Who What IEEE P /152 -na- 23 Oct95 Mark Laubach Birthday version of formal proposal submitted to P for the November, 1995 IEEE 802 Plenary meeting. IEEE P /152 and ATM_Forum/ IEEE P /152R1 and ATM_Forum/ R1 Future IEEE P /152R2 and ATM_Forum/ R2 -na- 1 Nov 95 Mark Laubach Created informational contribution for the ATM Forum. -na- 14 Jan 96 Mark Laubach Updated binary tree walk and truncated exponential binary backoff to directed exponential backoff. Updated acquisition protocol definition and state machine. Updated contention state FSM specification for station. Merged IEEE P /153 into this document. Modified and added additonal management messages. Further specified physical profile templates. Updated station states and definitions. Add physical channel definitions. Added interface support for ATM Forum Residential Broadband ADT and AIU Mar 96 Mark Laubach Removed LOAD and ASSIGN states. Fixed messages. Fixed typos and clarity of certain sections. Added C21 version. Modified: June 23, :44 am (V ) SCTE Contribution SCTE-DSS-97-xx

2 The UPSTREAMS Protocol for HFC Networks Standards Version Version Date Who What Future IEEE P /152R2 and ATM_Forum/ R2 Future IEEE P /152R2 and ATM_Forum/ R2 Future IEEE P /152R2 and ATM_Forum/ R2 IEEE P /152R2 and future ATM_Forum/ R2 SCTE Contribution SCTE-DSS SCTE Contribution SCTE-DSS-97-xx Mar 96 Mark Laubach Added specification for INVITE_INFO message to be sent using a preassigned multicast stration identifier. Change OAM format messages from a 1octet MTYPE to a 2 octet MTYPE. All messages have been change to realign fields to align to 16-bit and 32 bit boundaries Mar 96 Mark Laubach Created external standards version of the community protocol Aug 96 Mark Laubach Updated state machines and messages based on internal redesign work for performance improvements. Chapters 7 and 8 replaced with new chapters Sep 96 Mark Laubach Updated description of various chapters Oct 96 Mark Laubach Version of document for SCTE submission. Includes more descriptive text for layer services. Details on security have been added June 97 Mark Laubach Version of document for formal SCTE call fo submissions on 23 June 97. Page ii (V ) SCTE Contribution SCTE-DSS-97-xx

3 Table of Contents 1.0 Introduction Contact Information SCTE Data Standards Subcommittee Statement IEEE Working Group Statement SCTE Data Standards Subcommittee Executive Summary Meeting the 15 Criteria of SCTE-DSS Substantially Complete Protocol Summary UPSTREAMS Overview Basic Concepts CATV Node Models Architectural Perspectives Architecture Organization Layer Interfaces Application Areas Notation State Diagram Conventions Service Specification Method and Notation Classification of Service Primitives PHY Profiling References Overview Head-End Controller Subscriber Terminal Equipment or Stations Subnetwork Downstream and Upstream Architecture Media Access Control Protocol Summary Acquisition and Registration Overview Bandwidth Management for the Upstream Resources Station Responsibilities Head-End Controller Responsibilities ATM Forum Residential Broadband Support Head-End Controller Functional Architecture UPSTREAMS Head-End MAC Layer Functions ATM Transmission Convergence Emulation Function Physical Layer Functions Transmission System Transmission Layer Convergence Function Physical Layer Management Entity (PHY-LME) Head-End MAC Layer Functions ATM and Common Functions Bandwidth and Session Manager ATM AAL5 Common Part Convergence Functions MAC Ethernet Service Specific Convergence Function Page iii SCTE Contribution SCTE-DSS-97-xx (V )

4 Layer Management Functions Station Functional Architecture UPSTREAMS Station MAC Layer Functions ATM Transmission Convergence Emulation Function Physical Layer Functions Transmission System Transmission Layer Convergence Function Physical Layer Management Entity (PHY-LME) Station MAC Layer Functions ATM, Common, and Scheduling Functions ATM AAL5 Common Part Convergence Functions Ethernet Service Specific Convergence Function Layer Management Functions Convergence Sublayer Services Specification Scope and Field of Operation MAC Ethernet / Bridge Service General Description of Services Provided by the Sublayer Model Used for the Service Specification Overview of Interactions Basic Services and Options Detailed Service Specification ETHER_FRAME.request ETHER_FRAME.confirm ETHER_FRAME.indication ATM Sublayer Services Specification General Description of Services Provided by the Sublayer Model Used for the Service Specification Overview of Interactions Basic Services and Options Detailed Service Specification _UNITDATA.request _UNITDATA.indication _RESERVATION.request Physical Layer Services Specification Scope and Field of Operation PHY Service General Description of Services Provided by the Sublayer Model Used for the Service Specification Overview of Interactions Basic Services and Options Detailed Service Specification PHY_UNITDATA.request PHY_UNITDATA.indication PHY_RESERVATION.request PHY_RESERVATION.indication PHY_INFO.indication Physical Channel Specifications Downstream RF Page iv (V ) SCTE Contribution SCTE-DSS-97-xx

5 5.1.1 Modem signal characteristic FEC and Interleaving Head End Modulator Station Receiver Demodulator RF signalling characteristics General specification Head End Transmitter RF specification Station Receiver RF specification Physical Interface Upstream RF Modem signal characteristic FEC Station Modulator Head-end Demodulator Burst Receiver Upstream RF signalling characteristics Physical Interface Transport layer Protocol Data Unit Structures MAC Station Identifier Format Individual Identifier Station Unique Identifier Station Upstream Identifier Restrictions Group Identifier Receiver Group Identifier ATM Cell Overview Downstream ATM Cell Format Upstream ATM Cell Structure PHY Channel Framing Detail Downstream Slot Format Upstream Slot Structure UPSTREAMS Layer Operation Head End Controller States OFF-LINE RESET ACTIVE Head End Bandwidth and Station Management Null Cell Idle Bandwidth Manager Acquisition Process Station States Common Elements INVITE State INVITE State Message Primitives INVITE Message Flow SET State SET State Message Primitives SET State to Normal Protocol Operation State Message Flow SET State to HOLD State Message Flow Page v SCTE Contribution SCTE-DSS-97-xx (V )

6 Head-End INVITE and SET Message State Transitions HOLD State HOLD State Message Primitives IDLE State IDLE State Message Primitives ACTIVE Details ACTIVE State Message Primitives CONTENTION Details CONTENTION State Message Primitives CONTENTION WAIT Details CONTENTION WAIT State Message Primitives RESET Details RESET State Message Primitives Station State Summary Station Grant Processing Requirements Grant Processing Delay Null Grant Reception STU MAC Identifier Recognition Message Formats UPSTREAMS VCI Assignment UPSTREAMS Protocol Management Messages OAM-Like General Format Parameter Format Signed and Unsigned Integer Type, Length, Value (TLV) Grant Messages Grant Message Format Packing Grants into an ATM OAM Cell Grant Message OAM Cell Field Details Cell Slot Synchronization (CS_SYNC) Protocol Management Commands Protocol Management Group Message Assignments GO_RESET Message INVITE_CONFIG Message INVITE_INFO Message GO_SET Message GO_SET_ACK Message SET_DONE SET_DONE_ACK SET_NEW_DOWNSTREAM GO_HOLD Message General Management Commands MGMT_STATION_PING MGMT_STATION_INFO MGMT_HEADEND_PING MGMT_HEADEND_INFO UPSTREAM s Encryption System Requirements Key management methods Page vi (V ) SCTE Contribution SCTE-DSS-97-xx

7 9.2.1 Symmetric-key encryption for key distribution Public-key encryption for key management CFB DES ECB mode CFB encryption CFB decryption CFB applied to UPSTREAM Downstream details Head-End encryption details station decryption details Upstream details station encryption details Managing Key Lists Key Exchange Protocol Diffie-Hellman key exchange Algorithm Key exchange messages A Secure Key Generator for station and Head-End Overview Encryption Messages Security Info Req Security Info Security Info Ack Head-End Public Number station Public Number station Unicast Verify Head-End Unicast Verify Multicast Key Multicast Key Ack Multicast Verify Unicast Key Exchange Multicast Key Exchange Page vii SCTE Contribution SCTE-DSS-97-xx (V )

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9 Introduction 1.0 Introduction This document is called The UPSTREAMS Protocol for Sharing Transmission Resources among Entities using an ATM-based Messaging System (UPSTREAMS) Protocol for HFC Networks. This document is intended to be a specification document whose content will be shared with the SCTE Data Standards Subcommittee, the ATM Forum Residential Broadband Working Group, and the IEEE Cable TV MAC and PHY Working Group as part of the ATM over HFC standards proposal and definition process. UPSTREAMS should be considered as a Media Access Control (MAC) Protocol and a PHY specification for HFC networks. The specifications presented in this document should be considered as low risk. has products deployed successfully the field at many sites worldwide at this time that are based on this protocol. The demonstrated success of operational systems assures that products built to this specification will work as intended. NOTE: The specifications presented in this document are reducible to practice and meet the goals of both efficiency and good economics. In addition, the UPSTREAMS MAC algorithms (not including station management) are implementable in Application Specific Integrated Circuit (ASIC) technology. 1.1 Contact Information The UPSTREAMS protocol is a contribution of. The contact for this contribution is: Mark Laubach, Editor (408) Voice VP Technology (408) Main, Inc. (408) FAX 750 Tasman Drive laubach@com21.com Milpitas, CA SCTE Data Standards Subcommittee Statement This is a formal submission to the SCTE HIgh Speed Data Working Group as part of the call for submissions for 23 June An executive summary for this SCTE submission follows on the next page. It is not the intent of this submission to compete with the MCNS submission. Rather, the intent of this submission by is to have SCTE consider endorsing this protocol as one that meets the SCTE criteria for high speed data communications systems which support integrated services. is awaiting an intellectual property policy statement from the SCTE Data Standards Subcommittee before issuing any release statement. Normally, will release its intellectual property for licensing on a non-discriminatory basis for a reasonable fee consistent with the policy found in other public standard organizations. Note: due to the history of this protocol being submitted into , this document contains many words and phrases consistent with an proposal. Please translate any isms into SCTE isms or general isms as necessary. Page 1 SCTE Contribution SCTE-DSS-97-xx (V )

10 Introduction Note: The specifications contained in this document should be considered as Version 1 of the UPSTREAMS protocol. This base protocol provides support for a variety of services. Future services and/or extensions can be built upon the Version 1 specification. maintains ownership of this protocol. However, if the SCTE process elects to endorse this protocol will consider augmenting this specification based on the public input received during the SCTE call for submission process with the requirement that the Version 1 base protocol operation is maintained as the default and backward compatibility is maintain so that support for existing deployed systems and subscriber terminal units (stations) is guaranteed. 1.3 IEEE Working Group Statement Version 1 of this protocol proposal was submitted to the IEEE Cable TV MAC and PHY Working Group on 23 October The, Inc. intellectual property content of this proposal has been released for licensing on a non-discriminatory basis for a reasonable fee to the IEEE 802 Committee s Working Group CATV MAC and PHY standards development effort as per a separate letter. As per the passed motion at the IEEE P meeting during the plenary meeting in Maui, Hawaii, in July 1995: it is believed that this proposal contains sufficient information regarding bits, bytes, and operational details such that modeling and simulation of the UPSTREAMS protocol can be performed. 1.4 SCTE Data Standards Subcommittee Executive Summary Meeting the 15 Criteria of SCTE-DSS-96-6 The following section provides responses to the 15 criteria as documented in SCTE- DSS-96-6 as required by the SCTE DCS 23 June 1997 call for submissions. 3.1 Downstream PHY In the downstream direction, the data over cable system shall be capable of operating within the limits of any standard, HRC or IRC 6-MHz NTSC TV channel between 50 and 800 MHz defined by EIA Standard 542. The additional band above 750 MHz is to permit operation in the roll-off region of 750-MHz systems where group delay and losses permit. CMTS equipment might be offered in two overlapping frequency ranges within the upper range 300 to 800 MHz. The downstream modulation type shall be 64/ 256 QAM, per ITU-R Recommendation J.83 Annex B, plus variable-depth interleaving selectable by the operator and discovered by the CM. By nature of the ATM interface between the system components, the architecture provides a Physical Transmission Convergence (PHY-TC) sublayer for the downstream channel. This version supports the following downstream channel specifications: ITU-R Recommendation J.83 Annex B: Parameter Value Center Frequency 88 to 800 Mhz Page 2 (V ) SCTE Contribution SCTE-DSS-97-xx

11 Introduction Parameter Value Level Modulation Type Adjustable over the range of 50 to 61 dbmv 64 QAM Symbol Rate (nominal): 64 QAM Msym/sec The UPSTREAMS protocol allows extensibility. Future versions can easily support any of the following options: ITU-R Recommendation J.83 Annex B with the optional variable-depth interleaving, with options to accommodate requirements by the SCTE DVS standards working group and MCN ITU-R Recommendation J.83 Annex A and C, with options or extensions to accommodate requirements of DAVIC/DVB Optional use of MPEG2-TS PID multiplexing The layer independence provided by the PHY-TC sublayer to the MAC sublayer permits the addition of future downstream channel specifications. Any such additions are beyond the scope of this initial specification. Additions can be incorporated via future revisions to this document. 3.2 Upstream PHY In the upstream direction, the data over cable system shall be capable of operating on any frequency within the band 5 to 40 MHz, with variable channel widths. The upstream modulation type shall be QPSK or 16 QAM. These parameters shall be configurable by the operator and discovered by the CM. An evolution strategy to future new upstream PHYs should be taken into account. This specification employs a Physical Transmission Convergence (PHY-TC) sublayer for the upstream channel. The specification supports QPSK only, with frequency ranges from 5 to 40 MHz, with the following symbol rates and channel widths: Symbol Rate (ksym/sec) Channel Width (khz) a a. Channel width is the -30dB bandwidth The layer independence provided by the PHY-TC sublayer to the MAC sublayer permits the addition of future upstream channel specifications. Any such additions are beyond the scope of this specification. Additions can be incorporated via future releases of new version. Note that advanced modulation techniques, multicarrier or spread spectrum can be easily incorporated into the system. 3.3 Forward Error Correction FEC shall be provided in the downstream FEC, and should be considered for specification in the upstream direction. The operation of FEC in either direction shall be selectable by the operator and discovered by the CM. Page 3 SCTE Contribution SCTE-DSS-97-xx (V )

12 Introduction This specification provides FEC in the downstream channel according to ITU-R Recommendation J.83 Annex B based on the initial specification. As such, the FEC is not selectable in the first version. This specification provides FEC in the upstream channel on a burst basis. The amount of FEC is fixed for the upstream burst. Future versions of this protocol can add in selectable FEC. 3.4 Downstream Frequency Acquisition On initialization or after signal loss, the CM should scan the downstream 6-MHz channels for a valid downstream signal. If it has retained in memory the settings from previous operation, it should start with those. If none are in memory or it does not find a valid corresponding downstream signal, then it should scan a configurable quantity of preselected downstream channels within 2 minutes, and then the entire downstream band, until it finds a valid downstream signal. When it has found a valid downstream signal, it should store the parameters for later power-up. This specification includes a registration procedure for automatically acquiring and registering a station with the headend controller. The specification requires that certain parameter values are retained in non-volatile storage in the station. Among these parameters are the last downstream channel acquired parameters. Details on the registration procedure are contained later in this specification. 3.5 Link-Level Encryption Link-level encryption required in both directions. This specification provides link encryption on the downstream channels and on the upstream channels. The specification provides DES support with 40 bit or 56 bit keys. Diffie-Hellman is used for public key exchange. Details are provided in the Security chapter. 3.6 Layer Decoupling The PHY and MAC layers shall be completely decoupled in the two directions. The architecture provides a layer independent model consistent with IEEE 802 and OSI layer models. The MAC sublayer is independent from the PHY layer (upstream and downstream) in both the headend controller and the station. Upstream channels are decoupled from other upstream channels Downstream channels are decoupled from other downstream channels 3.7 Signaling The downstream MAC and PHY protocols shall support in-band signaling for upstream frequency and level control. The MAC messaging supports inband control of station operation, including support for upstream channel profile parameter selection, power level, frequency, and timing offset (ranging) control. Page 4 (V ) SCTE Contribution SCTE-DSS-97-xx

13 Introduction 3.8 Configuration of Channels The operator shall be able, at a CMTS, to configure an arbitrary quantity of forward channels partitioned in space/frequency associated with an arbitrary quantity of reverse channels partitioned in space/frequency. This document specifies a single downstream channel with multiple upstream channels. The specification does not preclude the use of multiple downstream channels. Future work will address the use of multiple downstream channels. 3.9 Levels of Service The PHY and MAC protocols shall support various levels of service, including contention-based ABR, and several intermediate "soft" guaranteed services. The operator shall be able to select these service levels on a modem-by-modem basis and/or on an service-by-service basis. It is expected that the design of the MAC protocol will pay particular attention to providing underlying support for IETF standards for real time traffic (i.e., RTP, RSVP, IPng flows). Hooks shall be provided for evolution to continuous bit rate services and ATM. There should be control of the maximum allowed upstream and downstream data rates per modem. This specification provides an ATM cell relay service. The MAC and PHY have been designed and engineered to support the Traffic Management Version 4.0 services classes for Constant Bit Rate (CBR), Variable Bit Rate (VBR), Available Bit Rate (ABR), and Unspecified Bit Rate (UBR), and their associated bandwidth delivery and Quality of Service (QoS) requirements. The specific scheduling support for these services is left to the vendor. The flexible scheduling support and allocation nature of the MAC and PHY allow support for the less-stringent needs of the IETF integrated services for guaranteed and elastic services Traffic Filtering The CM shall filter the traffic into the HFC. The CM shall support multiple PCs on a single 10baseT interface, and the maximum number of PCs allowed on a given minihub for a particular CM shall be selectable by the operator. This system is a cable television RF MAC and PHY protocol which permits the layering of other services, such as IEEE 802.1D bridging services. The specific filtering features of these bridging services is beyond the scope of this document Spectrum Management The operator shall be able to retune a CMTS and CMs to new spectrum slices. This specification will provide the necessary management support in every sublayer for incorporation into a MIB agent for external management of a system based on this specification. Specific operations of retuning to new RF spectrum slices is supported. Note: the UPSTREAMS MIB is not contained in this document Automatic Ranging A CM shall continuously monitor its timing with respect to the CMTS, and automatically adjust its transmission timing based on distance from the CMTS. The registration procedure provides for the initial automatic adjustment of timing offset (ranging). In addition, each upstream channel is required to produce timing offset infor- Page 5 SCTE Contribution SCTE-DSS-97-xx (V )

14 Introduction mation for each received burst allowing a management system to continuously monitor and adjust timing Automatic Power Adjustment A CM shall continuously monitor its transmission power with respect to the HFC losses to the CMTS, and automatically adjust its transmission power level. The registration procedure provides for the initial automatic adjustment of station transmission power. In addition, each upstream channel is required to produce received power information for each received burst allowing a management system to continuously monitor and adjust station transmission power Authentication Registration and Self-Discovery A new CM shall establish an authenticated relationship with the corresponding CMTS.The process will be completely automatic, with no data needed to be provided by either the operator or the user. The CM and the CMTS shall automatically discover the network location of the new CM and establish the authenticated relationship. The security authentication and registration procedures presented in this specification are intended to be automatic Support of Higher Levels of Capability Upon registration, or in response to a reset command sent from the head end, the cable modem shall revert to operation at a specified set of physical layer parameters and handshake with the head end. Following the handshake, a negotiation shall take place that configures the CM to operate compatibly with the headend at the highest possible level of performance. If necessary, the result of the negotiation and reconfiguration may be to reassign the cable modem to a new set of frequencies so that the system can allow older, less capable, CMs to continue to be supported by the system. This specification allows the head-end controller to tune stations for highest performance, including, but not limited to: Use of available bandwidth on a single upstream or downstream channel Load balancing of stations across multiple channels Automatic frequency hopping of stations to channels for error performance reasons Optimizing resource allocation for established Quality of Service (delay, jitter, loss) requirements for single and integrated services provided through the station Substantially Complete The UPSTREAMS protocol presented in this specification is substantially complete for a MAC and a PHY protocol specfication. The call for submissions for SCTE DSS requires a substantially complete submission however, the specific scope of completeness was not specified at the Orlando DSS meeting on 3 June Therefore, we are hoping that a substantially complete MAC and PHY specification meets the understanding of substantially complete. Page 6 (V ) SCTE Contribution SCTE-DSS-97-xx

15 Introduction 1.5 Protocol Summary The UPSTREAMS MAC and PHY protocols are only components of a fully deployed system compatible with the and/or ATM Forum Residential Broadband future standards directions. UPSTREAMS is an ATM over HFC Media Access Control (MAC) protocol. The UPSTREAMS protocol itself is not a traffic management scheduler, but rather a protocol messaging system that can support one of several bandwidth management models; e.g., a best effort Ethernet-like management model and/or a scheduling model with constant and best effort bit rate. An example of a bandwidth manager is presented in this document. UPSTREAMS resource management support is capable of integrating with an ATM layer to provide the full suite of ATM traffic management classes: CBR, Variable Bit Rate (VBR), Available Bit Rate (ABR), and UBR. The proposal specifies a downstream PHY and an upstream PHY. The PHY mod/ demod specifications are based on commercially available components. The head-end controller is responsible for all bandwidth management and all resource management of the segment, including profile assignment, modulation, frequency, bandwidth, and power assignment. The protocol is designed to support all Hybrid Fiber-Coax (HFC) models, i.e., combined returned and separate return systems over a homes passed size of 500 up to 1200 homes, and then possibly up to a maximum of 4K homes. With the assumption of one subscriber terminal equipment unit per home. An extension to support Telco-Return is discussed. The downstream is divided into ATM cell sized slots. The upstream is divided into slots which contain ATM cells. A request and grant style of bandwidth allocation is used to allocate slots in the upstream. A contention protocol slot is used to reduce polling requirements and improve upstream latency for making requests. An ATM Network-to-Network Interface (NNI) cell format is used as the basic information exchange data unit for both the downstream and upstream traffic flows. The larger 12-bit Virtual Path Identifier (VPI) of the NNI cell maps directly to a the MAC protocol station address. Station addresses are issued during the initial registration and acquisition process. Unicast, multicast, and broadcast addressing is supported in the downstream. Single-cell ATM messages are used for all downstream traffic, including but not limited to normal user data traffic, upstream resource management traffic, encryption management traffic, Operations, Administration, and Management (OAM) traffic, etc. Per cell overhead is limited to: 1 octet of security envelope overhead in the downstream, and 1 octet of both security envelope and station request information in the upstream. The UPSTREAMS MAC is independent of the Physical (PHY) layer, so long as the Physical Transmission Convergence (TC) layer supports specific basic framing functionality and a one-transmitter to many-receiver model is supported in the Page 7 SCTE Contribution SCTE-DSS-97-xx (V )

16 Introduction downstream and a many-transmitter to one-receiver model is supported in the upstream. Downstream and upstream encryption key management for the ATM payload is supported; although the actual encryption is done in the PHY TC layer. Encryption is transparent to the user data flow. Ethernet, 802.3, LLC, IP, and other service overlays are accomplished using an ATM AAL5 Segmentation and Reassembly (SAR) function. IEEE 48-Bit Link Layer Control (LLC) MAC addresses are used to identify all stations and is communicated between stations during registration acquisition and in all Ethernet/LLC frames. 1.6 UPSTREAMS Overview Basic Concepts The UPSTREAMS media access method is a means by which two or more stations share a common set of transmit and receive radio frequencies (RF) over a Hybrid Fiber- Coax Cable TV (CATV) subnetwork segment for the purposes of exchanging ATM messages. Stations are deployed along the physical CATV plant, each being a discoverable propagation delay distance from the head-end controller. A subnetwork segment has one designated controller which resides at a CATV network distribution point called a head-end location. This controller has responsibility for managing all resources supplied to it and in particular, the allocation of downstream and upstream message resources over the PHY interfaces assigned to it. The notion of a subnetwork segment is a basic building block, similar in concept to an Ethernet or IEEE subnetwork segment. The sharing discipline on the downstream RF channel is a one-to-many method, where the head-end transmitter broadcasts to all stations on the common RF channel. Messages from the head-end controller may either be unicast, multicast, or broadcast. The sharing discipline on the upstream RF channel is a many-to-one method, in that many stations are sharing the same upstream RF channel. Messages are always unicast and sent from the station to the head-end controller. To transmit, a station must have permission from the head-end controller to use a portion of the upstream RF channel resources. These permissions are allocated in the form of a contention grant, direct grant, or as an acquisition grant. The basic method of operation is that each station must request upstream resources, using a resource request message. Resource requests are transmitted to the head-end controller as a response to a contention grant, or as part of the overhead with each message sent as a response to a direct grant. The head-end controller accumulates resource requests from all stations and apportions upstream resources appropriate to meeting the fair needs of all stations. Station responses to contention grants are processed using a version of an adaptive p- persistent protocol called directed exponential backoff for the 1 contention mechanism in the slot(s) assigned in the grant. Direct grants are non-shared allocations, each to a specific station. An acquisition grant is used as part of the new station registration process. 1. In general, the same mechanism as specific in IEEE Page 8 (V ) SCTE Contribution SCTE-DSS-97-xx

17 Introduction All grants assign resources based on the location of an upstream frame which is common knowledge to all active stations. The upstream frame is synchronized to a downstream frame. For each station, the relation of its notion of the upstream logical frame timing to the downstream frame reception is set as part of the acquisition process. A Time Division Multiplexing (TDM) technique is used on the upstream channel; i.e., the upstream is slotted, an UPSTREAMS message is placed within a slot and upstream slots are numbered. All grants then specifically assign a small window of resources based on the notion of slot number and number of slots to use for the grant. All grants are renewable, in that they expire immediately after their grant window. All grants are sent as ATM messages in the downstream channel. One ATM message may contain many direct grants, each to a different station. All stations on an UPSTREAMS segment are assigned a unique logical station identifier as part of the acquisition process. This is called the Station Unique Identifier (SUID). This identifier is then used to send messages to that station. Station identifiers are not persistent, in that each time a station is powered up, is will be assigned its station identifier during the acquisition process. Stations are also assigned one or more station multicast addresses. The IEEE 48-bit MAC address of the station is discovered by the headend during the acquisition process. The head-end controller maintains a mapping of MAC address to logical station address. Each UPSTREAMS message contains only the logical subnetwork station identifier. IEEE 802 frames are transmitted between the head-end and all stations using ATM Adaptation Layer 5 (AAL5). Specifically, this proposal requires that all stations participating in supporting any 802 layer frame transmission are required to use AAL5 segmentation and reassembly techniques over the ATM facilities provided by the UPSTREAMS protocol. This is a proposal for Local Area Networks employing UPSTREAMS as the access method for network segments. This proposal is intended to encompass several PHY media types and techniques for upstream and downstream RF channel rates from 1.5 Mbps to 30 Mbps. This edition of this proposal provides the necessary specification and related parameter values for a 30 Mbps downstream channel which is associated with up to several individual 2.5 Mbps upstream channels. It is expected that subsequent editions of this proposal will provide similar specifications for the specific PHY types selected by the working group CATV Node Models The UPSTREAMS protocol has been designed to operate in HFC architectures that have either single return, or combined return plants. Single/combined return plants shown in Figures 1 and 2, and the separated return plant is shown in Figure 3. It should be noted that the separated return plant requires that the PHY must support one downstream channel and at least four separate upstream PHY channels, one from each physical return plant. Page 9 SCTE Contribution SCTE-DSS-97-xx (V )

18 Introduction Figure 1 HFC Node Case 1: Single Return Plant, One Geographic Area Head-End / Distribution Hub Optical Distribution Network Coaxial RF CATV Distribution Network To: A Mhz e/o AM Fiber Fiber Node o/e From: A 5-42 Mhz e/o AM Fiber o/e A Geographic Area: 500 homes each area (Examples:Cablelabs High Speed Cable Modem Service RFP homes served) Figure 2 HFC Node Case 2: Combined Return Plant, Four Geographic Areas Head-End / Distribution Hub Optical Distribution Network Coaxial RF CATV Distribution Network To: A-D From: A-D Mhz 5-42 Mhz e/o e/o AM Fiber AM Fiber Fiber Node 1:4 optical split A o/e o/e o/e B o/e o/e + C Geographic Areas: 125 to 500 homes each 500 to 2000 homes total D (Examples: TCI Cable Modem RFP - HFC1200 Model homes passed) Page 10 (V ) SCTE Contribution SCTE-DSS-97-xx

19 Introduction Figure 3 HFC Node Case 3: Separate Return Plant, Four Geographic Areas: Head-End / Distribution Hub Optical Distribution Network Coaxial RF CATV Distribution Network To: A-D From: A From: B From: C From: D Mhz 5-42 Mhz Each De- Mux e/o e/o AM Fiber AM Fiber Fiber Node 1:4 optical split o/e o/e o/e o/e o/e Mux A B C D Geographic Areas: 120 to 500 homes each 480 to 2000 homes total (Example: TCI Cable Modem RFP - HFC300 Model homes passed total) (Example: PacTel Cable Modem RFI homes passed total) 1.7 Architectural Perspectives There are two important ways to view local area network design corresponding to 1. Architecture, emphasizing the logical divisions of the system and how they fit together 2. Implementation, emphasizing actual components, their packaging and interconnection. This proposal is organized along architectural lines, emphasizing the large-scale separation of the system into two fundamental sublayer parts: the Media Access Control (MAC) sublayer of the Data Link Layer, and the Physical Layer. Following the ATM layering model, the MAC sublayer will be divided into ATM sublayer components, and the PHY sublayer will be divided into a Transmission Convergence (TC) sublayer and an Physical Media Dependent (PMD) sublayer. These layers are intended to correspond closely to the lowest layers of the ISO Model for Open Systems Interconnection (See Figure 4 on page 12). The IEEE Logical Link Control (LLC) sublayer, optional IEEE 802.1D MAC Bridging sublayer, and MAC sublayer together encompass the functions intended for the Data Link Layer as defined in the OSI model. The MAC layer is subdivided into a number of sublayers which are ATM specific. (See Figure 5 on page 13). A Service-Specific Convergence Sublayer (SSCS) could be used to support a Service Access Point (SAP) with the LLC layer. The SSCS layer is supported by the AAL5 Common Part Convergence Sublayer (CPCS), which in turn is supported by the Segmentation and Reassembly (SAR) sublayer, which in turn is support by the ATM sublayer. Page 11 SCTE Contribution SCTE-DSS-97-xx (V )

20 Introduction Figure 4 UPSTREAMS Relationship to the OSI Reference Model OSI REFERENCE MODEL LAYERS IEEE 802 LAN APPLICATION PRESENTATION SESSION HIGHER LAYERS LLC LOGICAL LINK CONTROL TRANSPORT NETWORK DATA LINK PHYSICAL 802.1D BRIDGING MAC UPSTREAMS ATM TC TRANSMISSION CONVERGENCE PMD PHYSICAL MEDIUM-DEPENDENT CATV MEDIA Page 12 (V ) SCTE Contribution SCTE-DSS-97-xx

21 Introduction Figure 5 ATM AAL5 Structure Relationship to UPSTREAMS MAC IEEE 802 LAN ATM AND AAL5 STRUCTURE HIGHER LAYERS LLC LOGICAL LINK CONTROL MAC UPSTREAMS ATM TC TRANSMISSION CONVERGENCE SERVICE SPECIFIC CONVERGENCE SUBLAYER COMMON PART OF CONVERGENCE SUBLAYER SEGMENTATION AND REASSEMBLY CONVERGENCE SUBLAYER AAL5 PMD PHYSICAL MEDIUM-DEPENDENT ATM LAYER CATV MEDIA The PHY layer subdivides into the TC sublayer and the PMD sublayer. Their respective responsibilities are show in Table 1:. Note that this list is not complete. The transmission Transmission Convergence Sublayer Physical Media Dependent Sublayer Slot and Cell delineation, downstream based on ITU I µsec clock recovery (subscriber terminal only) a Header Error Check (HEC) generation/verification Encryption / decryption of the ATM cell payload Forward Error Correction Downstream and Upstream Framing Upstream bandwidth request Bit timing RF Modulation Physical Medium Table 1: Physical Layer Functions (U-Plane) a. May be a requirement for ATM over HFC from the ATM Forum. Page 13 SCTE Contribution SCTE-DSS-97-xx (V )

22 Introduction system is proposed to be based on a PMD independent framing structure which provides the transport of ATM cells. It also provides overhead bytes for the carriage of encryption header and resource request information Architecture Organization An architectural organization of the standard has two main advantages: 1. Clarity. A clean overall division of the design along architectural lines makes the standard clearer. 2. Flexibility. Segregation of the medium-dependent aspects in the Physical Layer allows the LLC and MAC sublayers to apply to a family of CATV transmission media. Partitioning the Data Link Layer (into LLC and MAC) allows various media access methods within the IEEE 802 family of Local Area Network standards. Using ATM cells as the basic message unit across TC sublayer directly supports the use of ATM over Hybrid Fiber-Coax systems; i.e. ATM over The architectural model is based on a set of interfaces that may be different from those emphasized in implementations. One critical aspect of the design however shall be addressed largely in terms of the implementation interfaces: compatibility Layer Interfaces In the architectural model used here, the layers interact by way of well defined interfaces, providing services as specified in Chapter 2. In general, the interface requirements are as follows: 1. The interface between the MAC sublayer and the LLC sublayer includes facilities for transmitting and receiving frames, and provides per-operation status information for use by higher-level error recovery procedures. 2. The interface between the MAC sublayer and the PHY-TC sublayer includes facilities for transmitting and receiving ATM cells, transmitting and receiving resource management requests, and for determining frame timing and sequencing. These interfaces will be different for the head-end controller and for the station. Additional interfaces are necessary to allow higher level network-management facilities to interact with these layers to perform operation, maintenance, and planning functions, including but not limited to RF modem frequency selection, encryption key management, and the like. Network management functions will be discussed in a future version of this proposal. These interfaces will be described more precisely in later version of the UPSTREAMS document Application Areas The applications environment for the HFC LAN is intended to be home and small business environments. Use of HFC LANs in other environment, while not precluded, is not considered within the scope of this standard proposal. Page 14 (V ) SCTE Contribution SCTE-DSS-97-xx