1、ANSI INCITS 308-1997 (R2002)(formerly ANSI NCITS 308-1997)for Information Technology -Serial Storage Architecture Transport Layer 2 (SSA-TL2)American National Standardfor Information Technology -Serial Storage Architecture Transport Layer 2 (SSA-TL2)ANSI NCITS 308-1997SecretariatInformation Technolo
2、gy Industry CouncilApproved December 12, 1997American National Standards Institute, Inc.AbstractThis document describes the transport layer of the Serial Storage Architecture (SSA). SSA defines a se-rial interface hierarchy to be used for purposes within its distance and performance characteristics,
3、 includ-ing but not limited to storage subsystems.The Serial Storage Architecture fills a need in the evolution from parallel to serial interfaces for storagedevices. It meets the space constraints and cabling considerations for high-density storage arrays with acommensurate improvement in reliabili
4、ty and configurability. The reliability improvements are derivedfrom an architected error recovery, redundant paths to devices, a wrap mode for self-test, line fault detec-tion and a balanced signaling scheme that achieves a low error rate. The configurability results from theability to hot-plug dev
5、ices, the self-configuration capability, and the 20 meter length of cable segments.The algorithms for the web topology and transport mechanisms for the protocol services need to be de-fined in a manner that allows migration of the physical and protocol independently.Approval of an American National
6、Standard requires review by ANSI that therequirements for due process, consensus, and other criteria for approvalhave been met by the standards developer.Consensus is established when, in the judgement of the ANSI Board ofStandards Review, substantial agreement has been reached by directly andmateri
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11、standard. Purchasers of American National Standards mayreceive current information on all standards by calling or writing the AmericanNational Standards Institute.American National StandardPublished byAmerican National Standards Institute, Inc.11 West 42nd Street, New York, NY 10036Copyright 1998 by
12、 Information Technology Institute Council (ITI)All rights reserved.No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise,without prior written permission of the publisher.Printed in the United States of AmericaCAUTION:The developers of this standard
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14、 date of publication of this standard, following calls for the identification of patents thatmay be required for the implementation of the standard, notice of one or more claims has been re-ceived.By publication of this standard, no position is taken with respect to the validity of this claim or ofa
15、ny rights in connection therewith. The known patent holder has, however, filed a statement ofwillingness to grant a license under these rights on reasonable and nondiscriminatory terms andconditions to applicants desiring to obtain such a license. Details may be obtained from the pub-lisher.No furth
16、er patent search is conducted by the developer or the publisher in respect to any standardit processes. No representation is made or implied that licenses are not required to avoid in-fringement in the use of this standard.iContentsPageForewordvIntroduction . viii1Scope . 11.1 SSA-TL2 characteristic
17、s. 11.2 SSA family of standards . 22References . 32.1 Normative references . 32.2 Informative references 33Definitions, symbols, and abbreviations . 33.1 Definitions. 33.2 Symbols and abbreviations 54Conventions 65Data rate. 66Web 76.1 Strings 76.2 Loops 86.3 Complex Web containing switches. 878B/10
18、B code. 97.1 Data characters 97.2 Special characters 117.3 Initialization. 137.4 Code violations. 137.5 Permitted Special character sequences. 138Frames . 148.1 CONTROL field 158.2 STATUS field 178.3 EXT RSC field 178.4 PATH field 178.5 ADDRESS field. 178.6 DATA field 188.7 CRC field 189Protocol 199
19、.1 Router functions . 199.2 Web Routing. 199.3 Node routing. 229.4 Flow control 229.5 SAT. 259.6 Priority for transmission 3010Link management. 3010.1 Port attributes . 3010.2 Node based data structures . 35iiPage10.3 Beginning Communication process 3910.4 Speed Negotiation process 4010.5 Configurat
20、ion 4010.6 Resets 4111Error handling. 4411.1 Link ERP 4411.2 Invalid SMS field handling 4911.3 Asynchronous Alert process. 5111.4 De-queue Asynchronous Alert process 5111.5 ASYNC ALERT SMS Handling process. 5111.6 MASTER ALERT SMS Handling process 5412SSA message structures 5512.1 SMS validation . 5
21、612.2 TAG field values . 5712.3 Privileged SMS. 5812.4 Application SMS . 7813Transport layer processes 8313.1 Master Negotiation process 8313.2 Master Alive process 8513.3 SAT Region process 8513.4 Configutor Table Maintenance process 86Tables1Bit ordering in a byte 62Sustained data rate and maximum
22、 distance 735B/6B encoding rules . 1043B/4B encoding rules . 105Special characters 116User Defined character definition . 137Frame contents 158CONTROL field 159FRAME TYPE field. 1510RESET TYPE field . 1611RR flag values when entering the Enabled state . 2512RR flag values when entering the Ready sta
23、te 2513RR pending flag control 2514UNIQUE ID field . 3615Configuration table entry 3616Configutor table entry . 3717Configutor table entry STATUS field 37iiiPage18Node table entry . 3819Queued Asynchronous Alert table entry . 3820Asynchronous Alert Address table entry. 3921Link Status Byte 4622Recei
24、ver errors . 4723Recovery from corrupted ACK character pair. 4924Response to non-zero reserved fields or reserved code values. 5125Generic SSA message structure 5526SSA-TL2 messages supported. 5627ASYNC ALERT SMS 5828Format of the ALERT CODE field. 5829ALERT CODE values . 6030ASYNC REPLY SMS 6131RET
25、URN CODE field values 6132CONFIGURE PORT SMS 6233MODE field values 6334NEGOTIATE SPEED field 6335NEGOTIATE SPEED field effects on speed negotiation 6336DELETE RETURN PATH ID SMS 6437MASTER ALERT SMS . 6538QUERY NODE SMS. 6639SSA-TL VERSION field values . 6640QUERY NODE REPLY SMS 6741Upper-level prot
26、ocol code values . 6842QUERY PORT SMS . 6943QUERY PORT REPLY SMS 7044SUPPORTED SPEED field. 7045CURRENT SPEED field . 7146QUERY PROTOCOL SMS . 7147QUERY PROTOCOL REPLY SMS 7148QUERY REGISTRATION SMS 7249Configutor table returned data entry format 7350QUERY SWITCH SMS . 7351QUERY SWITCH REPLY SMS 745
27、2QUIESCE SMS. 74ivPage53REQUEST SAT REGION SMS 7554SAT OPCODE field 7655REQUEST SAT REGION REPLY SMS . 7756RETURN CODE values 7757RESPONSE SMS. 7758RETURN CODE values 7859DATA READY SMS 7860DATA REPLY SMS 8061DATA REQUEST SMS. 8162DATA REDIRECT SMS 82Figures1Relationship of the SSA standards. 22Dual
28、-port node 73String 84Dedicated connection. 85Loop . 86Complex Web containing a cyclic path. 97Generalized frame format. 148Specific frame format . 159ADDRESS field 1710Path addressing . 2111Timing of acknowledgments (non-Extended Distance Option operation) . 2412SAT operation for a loop 2713 SAT op
29、eration for a string 2814 Web with 2 SAT regions. 2815 State transitions 32AnnexesA Transport Layer Data Transfer Processes . 89B Transport Layer Services . 91C Examples of half and full duplex. 101vForeword (This foreword is not part of American National Standard NCITS 308-1997.)This standard was d
30、eveloped by Task Group T10.1 of Accredited Standards Commit-tee NCITS during 1996-97. The standards approval process started in 1997.This document includes three informative annexes which are not considered part ofthe standard.Requests for interpretation, suggestions for improvement and addenda, or
31、defect re-ports are welcome. They should be sent to the National Committee for InformationTechnology Standards (NCITS), ITI, 1250 Eye Street, NW, Suite 200, Washington,DC 20005.This standard was processed and approved for submittal to ANSI by NCITS. Com-mittee approval of this standard does not nece
32、ssarily imply that all committee mem-bers voted for its approval. At the time it approved this standard, NCITS had thefollowing members:James D. Converse, ChairKaren Higginbottom, Vice-ChairKate McMillan, SecretaryOrganization Represented Name of RepresentativeAMP, Inc. . Ben BennettEdward Kelly (Al
33、t.)Apple Computer, Inc. . David K. MichaelJerry Kellenbenz (Alt.)ATb) provide support for higher data rates in the physical layer 2 (SSA-PH2);c) enhance packet formats and addressing methods;d) define a transport layer acceptable to vendors looking for an evolution from parallel SCSI and systems des
34、igners looking foropportunities to more fully exploit the capabilities inherent to a serial bus; ande) cover other capabilities that fit within the scope of SSA-TL2 that may be proposed during the development phase by theparticipants in the project.This document defines the transport layer of the Se
35、rial Storage Architecture (SSA). SSA defines a serial interface hierarchy to beused for purposes within its distance and performance characteristics, including but not limited to storage subsystems. This standardis intended to be used with an upper layer protocol e.g., SCSI-2 Protocol (ANSI X3.294-1
36、996) or SCSI-3 Protocol (ANSI NCITS 309-1997) and a physical layer e.g., SSA Physical Layer 2 (ANSI NCITS 307-1997).1.1 SSA-TL2 characteristicsThe essential characteristics of SSA-TL2 are as follows:a) SSA-TL2 is optimized to minimize gate count while maintaining function and performance;b) SSA-TL2
37、provides a flexible addressing scheme to allow the configuration of a Web into dedicated connections, strings,loops, and complex configurations including a switch;c) the Web supports peer-to-peer communication with frame multiplexing between any pair of ports;d) the Web is self-configuring without t
38、he use of address switches;e) the link supports point-to-point physical connections only. Strings and loops are created by using dual port nodes with cut-through routing;f) an Extended Distance Option exists that allows 10 km between nodes through the use of additional buffering and anincreased ACK
39、time-out;g) allows operation at a distance of 2.5 km at a line data rate of 10 MB/s, and at a distance of 340 m at a line data rate of 40MB/s. The Extended Distance Option allows operation at a distance of 10 km at a line data rate of 40 MB/s. The actualdata rates and distances depend on the cable a
40、ssembly and the drivers and receivers used;h) the link makes optimum use of the physical medium by using full-duplex communication to avoid arbitration overhead andturn-around delay;i) full duplex communication achieves an aggregate 80 MB/sec bandwidth (40 MB/sec in each direction) between two ports
41、;j) the frames are constructed with a minimum framing overhead (e.g., only 8 characters of overhead for a 128-byte data field);k) an architected error recovery procedure provides transparent frame recovery after a transmission error;l) a Wrap mode is provided to allow fault isolation at a node;m) an
42、 optional line fault detector detects failures in the link;n) cyclical paths allow a Web to be configured providing redundant access to a node;ANSI NCITS 308-19972o) the transport layer is capable of simultaneously supporting multiple upper-level protocols (e.g., SCSI-2, SCSI-3, IPI-3,TCP/IP, etc.);
43、p) the 128-byte frame size minimizes the gate count needed for buffers.This standard defines the following functions:a) the protocol (e.g., framing, addressing, and flow control);b) link management (e.g., buffering, port states, resets, configuration, and error recovery).1.2 SSA family of standardsF
44、igure 1 illustrates the relationships of the SSA family of standards.1.2.1 SSA-S2PSerial Storage Architecture - (SSA-S2P) SCSI-2 Protocol defines the SCSI-2 Protocol used with SSA-TL1 or SSA-TL2.1.2.2 SSA-S3PSerial Storage Architecture - (SSA-S3P) SCSI-3 Protocol defines the SCSI-3 Protocol used wit
45、h SSA-TL2.1.2.3 SSA-TL1Serial Storage Architecture - (SSA-TL1) Transport Layer 1 defines the Transport layer that supports SSA-S2P and requires SSA-PH1.1.2.4 SSA-TL2Serial Storage Architecture - (SSA-TL2) Transport Layer 2 defines the Transport layer that supports SSA-S2P and SSA-S3P andrequires SSA
46、-PH1 or SSA-PH2.1.2.5 SSA-PH1Serial Storage Architecture - (SSA-PH1) Physical Layer 1 defines the Physical layer that supports SSA-TL1 and SSA-TL2, andconsists of the electrical characteristics of the interface and the connectors.1.2.6 SSA-PH2Serial Storage Architecture - (SSA-PH2) Physical Layer 2
47、defines the Physical layer that supports SSA-TL2, and consists of theelectrical characteristics of the interface and the connectors.Figure 1 - Relationship of the SSA standardsANSI NCITS 308-199732 References2.1 Normative referencesThe following standards contain provisions which, through reference
48、in this text, constitute provisions of this American NationalStandard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreementsbased on this American National Standard are encouraged to investigate the possibility of applying the
49、 most recent editions of thestandards listed below.Members of IEC and ISO maintain registers of currently valid International Standards, and ANSI maintains registers for AmericanNational Standards.ANSI X3.294-1996, Information Technology - Serial Storage Architecture - SCSI-2 Protocol (SSA-S2P)ANSI NCITS 309-1997, Information Technology - Serial Storage Architecture - SCSI-3 Protocol (SSA-S3P)2.2 Informative referencesThe following related standards are for informational purposes only, and do not contain provisions of this American National Standard.At the time of publication, the ed
