Tandem OSI/AS and OSI/TS Supplement (Includes RFC-1006 Support)

Networking and Data Communications Library Tandem OSI/AS and OSI/TS Supplement (Includes RFC-1006 Support) Abstract Part Number 107751 Edition This manual supplements the C30.08/D10 editions of the seven-manual set for OSI/AS and OSI/TS. It describes RFC-1006 support and other general changes to these manuals. First Published January 1995 Product Version Release ID D30.00 Supported Releases OSI/AS D30 and OSI/TS D30 This manual supports D30.00 and all subsequent releases until otherwise indicated in a new edition. Tandem Computers Incorporated

Document History Edition Part Number Product Version Earliest Supported Release Published First 107751 D30 D30.00 January 1995 New editions incorporate any updates issued since the previous edition. A plus sign (+) after a release ID indicates that this manual describes function added to the base release, either by an interim product modification (IPM) or by a new product version on a.99 site update tape (SUT). Ordering Information Document Disclaimer Export Statement Examples U.S. Government Customers For manual ordering information: domestic U.S. customers, call 1-800-243-6886; international customers, contact your local sales representative. Information contained in a manual is subject to change without notice. Please check with your authorized Tandem representative to make sure you have the most recent information. Export of the information contained in this manual may require authorization from the U.S. Department of Commerce. Examples and sample programs are for illustration only and may not be suited for your particular purpose. Tandem does not warrant, guarantee, or make any representations regarding the use or the results of the use of any examples or sample programs in any documentation. You should verify the applicability of any example or sample program before placing the software into productive use. FOR U.S. GOVERNMENT CUSTOMERS REGARDING THIS DOCUMENTATION AND THE ASSOCIATED SOFTWARE: These notices shall be marked on any reproduction of this data, in whole or in part. NOTICE: Notwithstanding any other lease or license that may pertain to, or accompany the delivery of, this computer software, the rights of the Government regarding its use, reproduction and disclosure are as set forth in Section 52.227-19 of the FARS Computer Software-Restricted Rights clause. RESTRICTED RIGHTS NOTICE: Use, duplication, or disclosure by the Government is subject to the restrictions as set forth in subparagraph (c)(1)(ii) of the Rights in Technical Data and Computer Software clause at DFARS 52.227-7013. RESTRICTED RIGHTS LEGEND: Use, duplication or disclosure by the Government is subject to restrictions as set forth in paragraph (b)(3)(b) of the rights in Technical Data and Computer Software clause in DAR 7-104.9(a). This computer software is submitted with restricted rights. Use, duplication or disclosure is subject to the restrictions as set forth in NASA FAR SUP 18-52 227-79 (April 1985) Commercial Computer Software Restricted Rights (April 1985). If the contract contains the Clause at 18-52 227-74 Rights in Data General then the Alternate III clause applies. U.S. Government Users Restricted Rights Use, duplication or disclosure restricted by GSA ADP Schedule Contract. Unpublished All rights reserved under the Copyright Laws of the United States.

New and Changed Information This manual supplements the C30.08/D10.00 editions of the seven-manual set for OSI/AS and OSI/TS: Tandem OSI/AS Configuration and Management Manual (part number 056781) Tandem OSI/TS Manual (part number 056782) Tandem OSI/AS Programming Manual (part number 056783) SCF Reference Manual for Tandem OSI/AS (part number 056787) SCF Reference Manual for Tandem OSI/TS (part number 056784) Tandem OSI/AS Management Programming Manual (part number 056785) Tandem OSI/TS Management Programming Manual (part number 056786) OSI/AS and OSI/TS Product Changes Enhancements to the OSI/AS and OSI/TS Manuals The changes to OSI/AS and OSI/TS are as follows: Tandem now offers an RFC-1006 implementation in OSI/AS and in OSI/TS. RFC- 1006 allows OSI/TS to connect to the Transmission Control Protocol (TCP), which is a Transport Layer Protocol specified in the Internet Reference Model. This manual also contains descriptions of external changes that have been made since the C30.08/D10.00 product release of OSI/AS and OSI/TS. This manual was produced in lieu of updating the OSI/AS and OSI/TS manuals for the D30.00 release. This supplement will be obsoleted in a future release; at that time, the information contained in this manual will be rolled into the appropriate OSI/AS and OSI/TS manuals. In addition to documenting the OSI/AS and OSI/TS product changes listed above, this manual provides corrections to Tandem Problem Reports (TPRs) issued against the C30.08/D10.00 release of the OSI/AS and OSI/TS manuals. 107751 Tandem Computers Incorporated iii

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Contents About This Manual ix Notation Conventions xiii Section 1 Introduction to RFC-1006 Overview of the Tandem OSI Architecture 1-1 TCP/IP as the NSP Process 1-3 Comparison of OSI and Internet Layer Architectures 1-4 OSI/AS and OSI/TS on Top of TCP/IP 1-5 Introduction to the Tandem TCP/IP Subsystem 1-7 TCP/IP Internet Addressing 1-9 Changes in the Transport Layer When Using RFC-1006 1-15 Transport Layer Protocols 1-15 Transport Service User Data 1-16 Transport Expedited Data 1-16 Larger TPDU Size 1-16 TPDU and Transport Packet Structure 1-16 Encapsulation of TPDU Into the Transport Packet 1-17 Transport Packet Format and Length 1-17 Service Primitives 1-18 Service Primitives Mapping Between OSI Network Service and TCP 1-21 Parameter Mapping Between OSI Network Service and TCP 1-23 Transport Service Procedures 1-23 Section 2 RFC-1006 Subsystem Configuration Configuring TCP/IP 2-1 Configuring OSI/TS 2-2 OSI/TS SCF Attributes Used for TCP/IP Protocol Selection 2-2 Configuring OSI/TS, TCP/IP, and NSP Processes 2-5 Single TSP Process Interfacing With a Single TCP/IP Process 2-8 Single TSP Process Interfacing With Multiple TCP/IP Processes 2-10 Multiple TSP Processes Interfacing With a Single TCP/IP Process 2-12 New OSI/TS Startup PARAMs for RFC-1006 2-13 Configuring OSI/AS 2-15 OSI/AS SCF Attributes Used for TCP/IP Protocol Selection 2-15 Section 3 RFC-1006 Changes to the SCF, SPI, and PTrace Subsystems OSI/TS SCF Commands Changed to Support RFC-1006 3-1 107751 Tandem Computers Incorporated v

Contents ALTER SERVICE #L4 3-4 ALTER SU 3-5 CHECK SU 3-6 INFO SERVICE #L4 3-10 INFO SU 3-11 STATUS SU 3-12 OSI/AS SCF Commands Changed to Support RFC-1006 3-14 IP Address in the ENTRY Object 3-15 ADD ENTRY #APPL 3-16 ADD ENTRY #NSAP 3-16 ADD ENTRY #SNPA 3-16 ADD PROCESS 3-17 ADD PROFILE #L4 3-18 ALTER ENTRY #APPL 3-19 ALTER ENTRY #NSAP 3-19 ALTER ENTRY #SNPA 3-20 ALTER PROCESS 3-20 ALTER PROFILE #L4 3-21 ALTER SERVICE #L4 3-22 CHECK ENTRY 3-24 CHECK SU 3-26 INFO ENTRY #APPL 3-30 INFO ENTRY #NSAP 3-30 INFO ENTRY #SNPA 3-31 INFO PROCESS 3-32 INFO PROFILE #L4 3-32 INFO SERVICE #L4 3-33 NAMES PROCESS 3-34 NAMES SUBSYS 3-34 STATUS SU 3-35 Other Useful SCF Commands 3-36 STATS SERVICE 3-36 INFO SUBNET 3-40 STATS SU Command 3-41 STATUS PROCESS Command 3-42 OSI/TS EMS Event Changed to Support RFC-1006 3-44 309: ZOS4-EVT-ACCESS-ERR 3-44 PTrace Records Changed to Support RFC-1006 3-47 OSI/AS PTrace Change 3-47 vi 107751 Tandem Computers Incorporated

Contents Section 4 OSI/TS PTrace Changes 3-47 RFC-1006 Configuration Command Files IP Address Conversion Program 4-1 OSI/AS Configuration Example 4-3 OSI/TS Configuration Example 4-5 OSI/MHS RS Group Configuration Example 4-8 Section 5 Section 6 Section 7 Section 8 TPDUs Used by RFC-1006 CC-TPDU 5-2 CR-TPDU 5-5 DR-TPDU 5-9 DT-TPDU 5-11 ED-TPDU 5-12 ER-TPDU 5-13 Socket Errors Returned by TCP/IP to OSI/TS Programming With the Sockets Interface Programming a Client 7-1 Programming a Server 7-2 General OSI/AS and OSI/TS Manual Changes and Corrections Index Figures Figure 1-1. Tandem OSI Architecture: OSI/AS and Underlying Subsystems 1-2 Figure 1-2. TSP Process Supporting Multiple NSP Processes 1-3 Figure 1-3. OSI and Internet Layer Architectures 1-4 Figure 1-4. Tandem OSI Architecture: OSI/AS and OSI/TS Over TCP/IP 1-5 Figure 1-5. OSI and TCP/IP Subsystem Interfaces 1-6 Figure 1-6. Tandem TCP/IP Subsystem With OSI/TS 1-7 Figure 1-7. Hosts and a Gateway in an Internetwork 1-10 Figure 1-8. Subnetworks 1-11 107751 Tandem Computers Incorporated vii

Contents Figure 1-9. Internet Address Formats 1-13 Figure 1-10. Internet Class B Address Format With a Subnet Address 1-13 Figure 1-11. Subnets on HOST9 1-14 Figure 1-12. Transport Packet 1-17 Figure 2-1. Configuring OSI/TS, TCP/IP, and NSP Processes in OSI/TS 2-6 Figure 2-2. Single TSP Process Interfacing With a Single TCP/IP Process 2-8 Figure 2-3. Single TSP Process Interfacing With Multiple TCP/IP Processes 2-10 Figure 2-4. Multiple TSP Processes Interfacing With a Single TCP/IP Process 2-12 Figure 4-1. OSI/MHS RS Group Interface to RFC-1006 4-8 Figure 5-1. CC-TPDU 5-2 Figure 5-2. Variable Part of the CC-TPDU 5-3 Figure 5-3. CR-TPDU 5-6 Figure 5-4. Variable Part of the CR-TPDU 5-7 Figure 5-5. DR-TPDU 5-9 Figure 5-6. Variable Part of the DR-TPDU 5-10 Figure 5-7. DT-TPDU 5-11 Figure 5-8. ED-TPDU 5-12 Figure 5-9. ER-TPDU 5-13 Figure 5-10. Variable Part of the ER-TPDU 5-14 Tables Table 0-1. Overview of the Contents of OSI/AS and OSI/TS Manuals ix Table 1-1. TCP and OSI Transport Class 4 Compared 1-15 Table 1-2. TPDUs Used by RFC-1006 1-16 Table 1-3. OSI Transport Service Primitives 1-19 Table 1-4. OSI Network Service Primitives 1-20 Table 1-5. Internet TCP Service Primitives 1-21 Table 1-6. Service Primitives Mapping 1-22 Table 1-7. Parameter Mapping 1-23 Table 2-1. OSI/TS SCF Attributes Used for TCP/IP Protocol Selection 2-2 Table 2-2. OSI/AS SCF Attributes Used for TCP/IP Protocol Selection 2-15 Table 5-1. TPDUs Used by RFC-1006 5-1 Table 7-1. Nowait Client and Server Steps 7-1 viii 107751 Tandem Computers Incorporated

About the OSI/AS and OSI/TS Manual Set About This Manual The OSI/AS subsystem and the OSI/TS subsystem together provide core services that support the seven-layer OSI Reference Model. With the addition of support for RFC- 1006, services are also provided to allow OSI applications to communicate over the Internet. The set of manuals for these two products is listed in Table 0-1. The table lists the tasks that the OSI/AS and OSI/TS manuals are designed to support and the type of information provided in each manual. Table 0-1. Overview of the Contents of the OSI/AS and OSI/TS Manuals This Manual Is Provided by This Manual and Other Manuals in the OSI Manual Set... Information on This Task... Supplement AS/PR AS/CM TS SCF/AS and SCF/TS AS/MPM and MPM/TS Planning an OSI application How How Designing and coding an OSI application How/Ref How/Ref Designing and coding a program to manage OSI subsystems How How How How/Ref Testing and debugging an OSI application, including error-recovery Ref Ref Testing and debugging a program to manage OSI subsystems, including error recovery Ref Ref Installing and configuring an OSI How/Ref How How Ref subsystem Starting an OSI subsystem How/Ref How How Ref Monitoring OSI connection activity How/Ref How How Ref Tuning for performance How/Ref How How Ref Troubleshooting an OSI configuration How/Ref How How Ref Key: How How-to information Ref Reference information Supplement AS/PR AS/CM TS SCF/AS SCF/TS AS/MPM TS/MPM Tandem OSI/AS and OSI/TS Supplement (Includes RFC-1006 Support) Tandem OSI/AS Programming Manual Tandem OSI/AS Configuration and Management Manual Tandem OSI/TS Manual SCF Reference Manual for Tandem OSI/AS SCF Reference Manual for Tandem OSI/TS Tandem OSI/AS Management Programming Manual Tandem OSI/TS Management Programming Manual 107751 Tandem Computers Incorporated ix

About This Manual What Is in This Manual? What Is in This Manual? This manual is intended to be used as a supplement to the seven-manual OSI/AS and OSI/TS set. Sections 1 through 6 provide information on Tandem s RFC-1006 implementation in OSI/AS and OSI/TS. RFC-1006 allows OSI/TS to connect to the Transmission Control Protocol (TCP), which is a Transport Layer protocol specified in the Internet Reference Model. Section 7 provides general information that applies to all the OSI/AS and OSI/TS manuals. Section 1, Introduction to RFC-1006, introduces the architecture and new features of the OSI/AS and OSI/AS subsystems when using RFC-1006. Section 2, RFC-1006 Subsystem Configuration, describes how to configure the OSI/AS and OSI/TS subsystems to use RFC-1006. Section 3, RFC-1006 Changes to the SCF, SPI, and PTrace Subsystems, describes changes made to the OSI/AS and OSI/TS Subsystem Control Facility (SCF) commands, the Subsystem Programmatic Interface (SPI) commands, and the PTrace displays. Also described is a change made to one of the OSI/TS Event Management Subsystem (EMS) messages. Section 4, RFC-1006 Configuration Command Files, provides sample files used to configure OSI/AS, OSI/TS, and OSI/MHS to use RFC-1006. Also described is a utility program that performs address conversion between two notations used to represent Internet protocol (IP) addresses as the NSAP address, a dotted decimal notation, and an eight-digit hexadecimal notation. Section 5, TPDUs Used by RFC-1006, describes the TPDUs that are used by RFC- 1006. Section 6, Socket Errors Returned by TCP/IP to OSI/TS, describes the programming steps that are required for a client or server program to communicate with TCP/IP. Section 7, Programming With the Sockets Interface, describes the programming steps that are required for a client or server program to communicate with TCP/IP. Section 8, General OSI/AS and OSI/TS Manual Changes and Corrections, contains information of general interest to OSI/AS and OSI/TS users (not just RFC-1006 users). This section documents external product changes that have been made since the C30.08/D10 release of OSI/AS and OSI/TS. This section also documents changes and corrections to the C30.08/D10 release of the OSI/AS and OSI/TS manuals. x 107751 Tandem Computers Incorporated

About This Manual Your Comments Invited What Is Not in This Manual? Configuration of the TCP/IP, X25AM, and TLAM subsystems is not covered in this manual; see the following manuals: Tandem TCP/IP Configuration and Management Manual SCF Reference Manual for Tandem TCP/IP Tandem TCP/IP Management Programming Manual TLAM Configuration and Management Manual System Generation Manual for X25AM Standards Implemented by Tandem OSI/AS and OSI/TS This manual and the other Tandem OSI manuals are written for those familiar with the OSI standards to which the Tandem OSI software conforms. These standards include the following: OSI Layer Standards For ISO Standard CCITT Standard (General) OSI Reference Model Abstract Syntax Notation-1(ASN.1) Basic Encoding Rules for ASN.1 ISO 7498 ISO 8824 ISO 8825 N/A ACSE (Application Layer) Service Protocol ISO 8649 ISO 8650 CCITT X.217 CCITT X.227 Presentation Layer Service Protocol ISO 8822 ISO 8823 CCITT X.216 CCITT X.226 Session Layer Service Protocol ISO 8326 ISO 8327 CCITT X.215 CCITT X.225 Transport Layer Service Protocol ISO 8072 ISO 8073 CCITT X.214 CCITT X.224 Network Layer Service IP & SNDCF protocol ES-IS protocol X.25 protocol NSAP addresses ISO 8348 ISO 8473 ISO 9542 ISO 8208 ISO 8348/ Addendum 2 CCITT X.213 CCITT X.223 CCITT X.25 Tandem OSI/AS and OSI/TS support the NIST Special Publication 500-150, stable implementations agreements for OSI protocols, December 1989. Tandem OSI/AS and OSI/TS support the Internet standard, RFC 1006, OSI Transport Service on top of the TCP. Your Comments Invited After you have had a chance to use this manual, please take a moment to send us your comments. You can do this by sending an Internet mail message to PUBS_COMMENTS@TANDEM.COM or by returning a Reader Comment Card. When you send an Internet mail message to us, you will automatically receive a response to acknowledge receipt of your message. A more detailed response will be sent later. Be sure to include your name, company name, address, and phone number 107751 Tandem Computers Incorporated xi

About This Manual Your Comments Invited in your message. If your comments are specific to a particular manual, include the part number and title of the manual in your message. The Reader Comment Card is located at the back of the printed manual and as a separate file in the CD Read Document List. You can fax the card to (408) 285-6660 or mail the card to the address printed on the card. Many of the improvements you see in Tandem manuals are a result of suggestions from our customers. Please take this opportunity to help us improve future manuals. xii 107751 Tandem Computers Incorporated

General Syntax Notation UPPERCASE LETTERS lowercase italic letters Brackets [ ] Notation Conventions The following list summarizes the notation conventions for syntax presentation in this manual. Uppercase letters indicate keywords and reserved words; enter these items exactly as shown. Items not enclosed in brackets are required. For example: CHECK SU Lowercase italic letters indicate variable items that you supply. Items not enclosed in brackets are required. For example: file-name Brackets enclose optional syntax items. For example: TERM [\system-name.]$terminal-name INT[ERRUPTS] A group of items enclosed in brackets is a list from which you can choose one item or none. The items in the list may be arranged either vertically, with aligned brackets on each side of the list, or horizontally, enclosed in a pair of brackets and separated by vertical lines. For example: LIGHTS [ ON ] [ OFF ] [ SMOOTH [ num ] ] K [ X D ] address-1 Braces { } Vertical Line A group of items enclosed in braces is a list from which you are required to choose one item. The items in the list may be arranged either vertically, with aligned braces on each side of the list, or horizontally, enclosed in a pair of braces and separated by vertical lines. For example: LISTOPENS PROCESS { $appl-mgr-name } { $process-name } [ EXPEDITED { ON OFF } ] A vertical line separates alternatives in a horizontal list that is enclosed in brackets or braces. For example: INSPECT { OFF ON SAVEABEND } 107751 Tandem Computers Incorporated xiii

Notation Conventions General Syntax Notation Ellipsis... Punctuation Item Spacing An ellipsis immediately following a pair of brackets or braces indicates that you can repeat the enclosed sequence of syntax items any number of times. For example: M address-1 [, new-value ]... [ - ] {0 1 2 3 4 5 6 7 8 9}... An ellipsis immediately following a single syntax item indicates that you can repeat that syntax item any number of times. For example: "s-char..." Parentheses, commas, semicolons, and other symbols not previously described must be entered as shown. For example: error := NEXTFILENAME ( file-name ) ; LISTOPENS SU $process-name.#su-name Quotation marks around a symbol such as a bracket or brace indicate the symbol is a required character that you must enter as shown. For example: "[" repetition-constant-list "]" Spaces shown between items are required unless one of the items is a punctuation symbol such as a parenthesis or a comma. For example: CALL STEPMOM ( process-id ) ; If there is no space between two items, spaces are not permitted. In the following example, there are no spaces permitted between the period and any other items: $process-name.#su-name Line Spacing If the syntax of a command is too long to fit on a single line, each continuation line is indented three spaces and is separated from the preceding line by a blank line. This spacing distinguishes items in a continuation line from items in a vertical list of selections. For example: ALTER [ / OUT file-spec / ] CONTROLLER [, attribute-spec ]... xiv 107751 Tandem Computers Incorporated

1 Introduction to RFC-1006 This section contains the following information: Overview of Tandem OSI architecture Introduction to the Tandem TCP/IP subsystem Changes in the Transport Layer when using RFC-1006 Tandem OSI/AS and OSI/TS have implemented the Request for Comments (RFC) 1006 standard entitled ISO Transport Service on Top of the TCP, Version 3. This standard, developed for the Internet community, defines how the ISO transport service can be implemented on top of the Transmission Control Protocol (TCP), which is a Transport Layer protocol specified in the Internet Reference Model. Using the RFC-1006 standard, OSI applications such as X.400, X.500, and FTAM (and other OSI/AS or OSI/TS applications) that communicate over OSI/AS and OSI/TS can now communicate with other servers and clients over a TCP/IP network connection. RFC-1006 was implemented such that: No changes are required for existing upper layer applications that wish to use RFC-1006. No functional changes were made to OSI/AS and OSI/TS that would affect non- RFC-1006 users. No limitations are placed on the use of TCP/IP for RFC-1006 users. That is, RFC- 1006 users make use of TCP/IP as any other TCP/IP user would. Note Overview of the Tandem OSI Architecture The terms client and server are used in this manual as is customary in TCP/IP literature. A client is a process that sends requests to the server and waits for it to respond. A server is a process that offers a service that can be used over the network; it accepts a request, performs the specified service, and returns the result to the requester. The client-server model is the same model known in Tandem literature as the requester-server model (a client is the same as a requester). Throughout this manual, the term RFC-1006 (with a hyphen) refers to the Tandem implementation of the standard, and the term RFC 1006 (without a hyphen) refers to the RFC 1006 Internet standard. Figure 1-1 illustrates how the various layers of the OSI Reference Model are supported for users of OSI/AS and OSI/TS over: A local area network (LAN), the TLAM subsystem A wide area network (WAN), the X25AM subsystem The Internet (TCP/IP subsystem) Tandem OSI/TS connects to TCP/IP at the Transport Layer within the OSI/TS subsystem, by specifying TCP/IP as the Network Service Provider (NSP) process. TCP/IP, in turn, connects to X25AM and TLAM. 107751 Tandem Computers Incorporated 1 1

Introduction to RFC-1006 Overview of the Tandem OSI Architecture Figure 1-1. Tandem OSI Architecture: OSI/AS and Underlying Subsystems Layer Application Presentation Session Other OSI/AS Applications OSI/MHS Subsystem OSI/FTAM Subsystem OSI/TS Applications OSI/AS Subsystem Transport Network TCP/IP Subsystem OSI/TS Subsystem Data Link X25AM Subsystem TLAM Subsystem X25AM Subsystem TLAM Subsystem Controllers Controllers Controllers Controllers Physical RS-232C, RS-449, X.21, V.35 50-ohm Baseband RS-232C, RS-449, X.21, V.35 50-ohm Baseband WAN LAN WAN LAN 005 1 2 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Overview of the Tandem OSI Architecture TCP/IP as the NSP Process As with previous OSI/AS and OSI/TS releases, X25AM and TLAM may still be specified as NSP processes, but if you want to run OSI applications over the Internet, you instead specify TCP/IP as the NSP process. A single Transport Service Provider (TSP) process can support TCP/IP, X25AM, and TLAM connections simultaneously. You do not need to add a separate TSP process to use RFC-1006. Transport connections using X25AM or TLAM as the NSP can co-exist with transport connections using TCP/IP as the NSP. Configurations for existing applications using X25AM or TLAM as the NSP are not affected by adding applications that use RFC-1006. Figure 1-2 shows how a single TSP process (in the OSI/TS subsystem) can interface with multiple NSP processes. Figure 1-2. TSP Process Supporting Multiple NSP Processes Layer Transport Network NSP (TCP/IP) TSP NSP (X25AM) Data Link NSP (TLAM) NSP 010 When TCP/IP is the NSP process, it runs as a nonprivileged process in the Tandem TCP/IP subsystem. The TCP/IP process runs as a Tandem NonStop process pair that performs services for both client and server programs. It is the base process for all the other components of the Tandem TCP/IP subsystem. 107751 Tandem Computers Incorporated 1 3

Introduction to RFC-1006 Overview of the Tandem OSI Architecture Comparison of OSI and Internet Layer Architectures This section provides a brief summary of the OSI and Internet Layer architectures and describes how the OSI upper layers connect to the TCP/IP lower layers. Figure 1-3 shows each of the seven layers of the International Organization for Standardization (ISO) Reference Model with the comparable layer of the Internet Reference Model beside it. The Internet Reference Model has five layers. Figure 1-3. OSI and Internet Layer Architectures Upper Layers Application Presentation Session Application Lower Layers Transport Network Data Link Physical Transport Internet Network Interface Physical OSI Reference Model Internet Reference Model 015 1 4 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Overview of the Tandem OSI Architecture OSI/AS and OSI/TS on Top of TCP/IP Figure 1-4 shows the combination of the OSI upper layers and the TCP/IP lower layers. The three OSI upper layers remain the same and provide the application services. The OSI Transport Protocol Data Units (TPDUs) interface with the TCP/IP Transport Layer through the sockets interface. Figure 1-5 illustrates the subsystem interfaces. Figure 1-4. Tandem OSI Architecture: OSI/AS and OSI/TS Over TCP/IP Layers Services and Protocols Objects Passed Between Layers Application Applications/Application Services APDUs OSI/AS Presentation Application Services PPDUs Session Application Services SPDUs OSI/TS Transport OSI Transport Protocols TPDUs TCP/IP Transport Internet Transmission Control Protocol Internet Protocol TCP Segments IP Datagrams Network Network Protocol Network-Specific Frames Physical Hardware Bits 020 Subsystem Interfaces As shown in Figure 1-5, OSI/TS interfaces with TCP/IP through socket library routines and with OSI/AS through file-system procedures. OSI/AS applications interface with the OSI/AS subsystem through the application programmatic interface (API) by calling Application, Presentation, and Session (APS) procedures. (The APS procedure calls provide a procedural interface to OSI/AS, just as the file-system procedures provide a procedural interface to the file system.) When the APS procedure is called to initiate a session, a presentation, or an ACSE operation, the API passes the request for services, if necessary, to one or more OSI/AS subsystem processes. These processes, in turn, may pass the request and associated data to the OSI/TS subsystem process through file-system procedures. 107751 Tandem Computers Incorporated 1 5

Introduction to RFC-1006 Overview of the Tandem OSI Architecture Figure 1-5. OSI and TCP/IP Subsystem Interfaces Tandem NonStop System Other OSI/AS Applications OSI/MHS Subsystem OSI/FTAM Subsystem OSI/TS Applications APS/API OSI/AS Subsystem File System OSI/TS Subsystem Sockets Library TCP/IP Subsystem File System X25AM Subsystem File System TLAM Subsystem File System X25AM Subsystem File System TLAM Subsystem 022 The sockets interface uses file-system procedures for interprocess communications and provides socket library routines for TCP users to OPEN and CLOSE connections and to SEND and RECEIVE data on established connections. 1 6 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Introduction to the Tandem TCP/IP Subsystem A Tandem TCP/IP subsystem runs on the Tandem NonStop Kernel operating system over a TLAM or X25AM I/O process. It has a wide range of capabilities provided by a number of individual components that act alone or together. Figure 1-6 shows the Tandem TCP/IP subsystem components and their relationships to the TLAM, X25AM, and OSI/TS subsystems. Figure 1-6. Tandem TCP/IP Subsystem With OSI/TS TCP/IP Subsystem FTP Server TELNET Subsystem ECHO Server FINGER Server Transfer Mail TFTP Server LISTNER Process SMTP DNS FTP Client OSI/TS Sockets Interface TFTP Client TCP/IP Process FINGER Client ECHO Client TELNET Client TLAM X25AM Controller Controller LAN Public Data Network (PDN) 025 107751 Tandem Computers Incorporated 1 7

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Sockets Interface The TCP/IP subsystem components interface with the TCP/IP process through the sockets interface, as shown in Figure 1-6. The Tandem socket library routines are based on the sockets programmatic interface primitives in the UNIX operating system (BSD 4.3). In addition, the Tandem socket library routines include extensions, such as NOWAIT I/O, to adapt the Berkeley sockets interface to the Tandem NonStop Kernel operating system. TCP/IP Subsystem Components The TCP/IP processes include the following processes and protocols, as described below. The TCP/IP process consists of the following protocols: The TCP protocol provides the transport control protocol. The User Datagram Protocol (UDP) is a connectionless transport protocol and provides different transport services. It is not used with RFC-1006. The Internet Protocol (IP) is the internetworking protocol, to ISO 8473 (CLNP). The Internet Control Message Protocol (ICMP) is a module within IP that reports errors and provides administrative and status messages. The Address Resolution Protocol (ARP) translates Internet protocol addresses to physical addresses and hides the physical addresses from the upper layers. The Subnetwork Access Protocol (SNAP) is a required interface between the IP layer and the Logical Link Control (LLC) sublayer in LANs. The File Transfer Protocol (FTP) is a widely used Application Layer standard used to transfer files between hosts. The Simple Mail Transfer Protocol (SMTP) is a widely used Application Layer standard that defines how to transmit mail messages between users. The FINGER protocol provides a means to obtain status information on users currently logged onto a particular system. The LISTNER process: In the Tandem TCP/IP environment, this process functions as a super server for ECHO, FTP, and FINGER and invokes the appropriate Tandem server as connection requests for FTP, ECHO, and FINGER services are received on well-known TCP ports. The OSI/TS server does not use the LISTNER process as do FTP, ECHO, and FINGER servers. The OSI/TS server directly performs PASSIVE opens by itself and does not rely on the LISTNER process. The TELNET subsystem provides a virtual terminal protocol that allows a user of one host to log onto to a remote host and to appear as a local user to the remote host. 1 8 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem See the Tandem TCP/IP Configuration and Management Manual for more information on Tandem TCP/IP components. TCP/IP Internet Addressing This section provides summary information on the Internet and Internet addressing. More detailed information on addressing is provided in the TCP/IP Configuration and Management Manual. Internet Concepts The Internet is a virtual network that consists of large numbers of interconnected, independent (often dissimilar) networks. Networks in the Internet are connected to each other by devices called either gateways or protocol converters, which function to translate dissimilar protocols. Each network consists of a number of systems, or hosts, connected by a common communications medium, or protocol. The addressing scheme used within TCP/IP provides a mechanism for all the parts to appear as a single network. Figure 1-7 illustrates an example of internetworking that is made up of two networks, several hosts and one gateway. In this figure, networks NETA and NETB are connected by the gateway system, HOST4. The three systems labeled HOST1, HOST2, and HOST3 belong to NETA. The other systems are connected to NETB. 107751 Tandem Computers Incorporated 1 9

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Figure 1-7. Hosts and a Gateway in an Internetwork Network NETA Internet Address = 98.0.0.0 Network NETB Internet Address = 37.0.0.0 HOST9 37.1.0.8 HOST1 98.0.2.9 HOST2 98.0.3.1 Gateway HOST4 98.0.1.6 37.0.4.1 HOST6 37.0.8.1 HOST7 37.0.3.9 HOST10 37.1.3.5 HOST11 37.2.2.9 HOST3 98.0.7.4 HOST8 37.0.3.2 HOST12 37.2.8.1 095 As described in RFC 950, each network can be divided into a number of subnetworks, or subnets. Within a network, each subnet is treated as a separate network; outside the network, the subnets appear as part of a single network. Each subnet attached to a host is reached through a device (or a pseudodevice, such as a loopback driver) that provides an interface for the Internet Protocol (IP) datagram transmission. In this manual, the term subnet is also used to refer to the interface through which the subnet is reached. The addressing of subnets within a LAN is accomplished by dividing the local address portion of the Internet address into a subnet number and a host number. The subnet number identifies the specific subnet, and the host number identifies the host system within the subnet. Figure 1-8 shows an example of the same network as shown in Figure 1-7, but with subnets added. In Figure 1-8, NETB consists of subnets NETC and NETD. To identify the portion of the Internet address that represents the subnet number, a 32- bit subnet mask is used. In the mask, all bits corresponding to the network address and its subnet address are set to 1, and all bits corresponding to the host within the subnet are set to 0. 1 10 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Figure 1-8. Subnetworks Network NETA Internet Address = 98.0.0.0 Network NETB Internet Address = 37.0.0.0 Subnet NETC Internet Address = 37.1.0.0 HOST1 98.0.2.9 HOST2 98.0.3.1 Gateway HOST4 98.0.1.6 37.0.4.1 Gateway HOST6 37.0.8.1 37.1.0.1 HOST7 37.0.3.9 HOST9 37.1.0.8 HOST10 37.1.3.5 Subnet NETD Internet Address = 37.2.0.0 HOST3 98.0.7.4 Gateway HOST8 37.0.3.2 37.2.0.1 HOST11 37.2.2.9 HOST12 37.2.8.1 100 Tandem TCP/IP Internet Concepts Usually a host has only one Internet address on each network it is attached to. Because of the multiprocessing nature of the Tandem NonStop system and the fact that more than one TCP/IP process can exist on a system, a Tandem system can appear to the outside world as more than one logical host on a network. Multiple TCP/IP processes in a system on the same network must be represented by multiple Internet addresses; this way, they will appear to the network as multiple hosts. Ports and Sockets Ports provide a multiplexing capability by allowing multiple applications to communicate concurrently with the same TCP/IP process. In this sense, a port number is similar to a service access point (SAP) in OSI. As mentioned earlier, the TCP/IP subsystem components interface with the TCP/IP process through the sockets interface (see Figure 1-6). A socket identifies an endpoint communications process. 107751 Tandem Computers Incorporated 1 11

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Every TCP/IP transport endpoint (socket) is addressable by the combination of an Internet protocol (IP) address and a port number. The connection between two applications can be identified by: The Internet address of the local node The port number of the application on the local node The Internet address of the remote node The port number of the application on the remote node Servers use ports 1 through 1023. Clients use ports 1024 and up. In the Internet, port numbers 1 through 255 are preassigned. These are called wellknown ports; they are used by servers to identify widely used applications called well-known services. TCP port 102 is reserved for OSI transport services implementing the RFC 1006 standard. (TCP/IP literature commonly refers to port 102 as being reserved for ISO-TSAP.) The well-known port is used between the two host computers to identify which application program is to receive incoming traffic. When using RFC-1006, clients specify well-known port 102 in connection requests. Servers listen on well-known port 102 for any incoming connection requests. Internet Address An Internet protocol (IP) address is a four-octet (32-bit) numeric value, composed of two parts: the network address, and the local address. The network address portion identifies a particular network, and the local address portion identifies a local host on that network. An IP address is usually specified in a dotted decimal notation, which represents 4 octets in ASCII, separated by periods; for example, 133.50.85.43. Each octet value is a number in the range 0 through 255. In OSI/AS and OSI/TS, an IP address can also be specified in an eight-digit (32-bits) hexadecimal string (the format used to enter an NSAP address); for example, 08000124, representing a class A address (network ID 8 and host ID 124 in hexadecimal). Section 3, RFC-1006 Changes to the SCF, SPI, and PTrace Subsystems, explains when to use each IP address format. An IP address is classified as class A, B, or C, depending on how the 32 bits are divided between the network address and the local address. Figure 1-9 shows the formats of the different IP address classes. 1 12 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Figure 1-9. Internet Address Formats Class A Address Bit 0 8 16 24 31 0 Network Address Local Address Class B Address Bit 0 8 16 24 31 1 0 Network Address Local Address Class C Address Bit 0 8 16 24 31 1 1 0 Network Address Local Address Note: Bit 0 is the most significant bit. 045 To address subnets within a LAN, the LAN administrator can further divide the local address into a subnet number that identifies a particular subnet and a host number that identifies a host system within the subnet. The subnet number is always in the most significant n bits of the local address (n varies depending on the address class). Figure 1-10 shows an example of a class B address in which the first 5 bits of the local address (bits 16 through 20) are designated as the subnet address, leaving the last 11 bits to identify the host (bits 21 through 31). Figure 1-10. Internet Class B Address Format With a Subnet Address Bit 0 15 16 20 21 31 Internet Address Network Address Subnet Number Host Number 050 107751 Tandem Computers Incorporated 1 13

Introduction to RFC-1006 Introduction to the Tandem TCP/IP Subsystem Tandem TCP/IP Subnet Addressing Tandem TCP/IP defines a IP address on a Tandem system by use of the TCP/IP SCF SUBNET object. Each subnet is represented by an IP address. Through each subnet, the TCP/IP process interfaces with each TLAM or X25AM IOP and controller. Figure 1-11 illustrates what subnets on HOST9 (shown in Figure 1-8) might look like. Figure 1-11. Subnets on HOST9 HOST9 OSI/TS TCP/IP1 Subnet1 IPAddress1 Subnet2 IPAddress2 TLAM1 TLAM2 Controller1 Controller2 051 You can add a maximum of 13 subnets to each TCP/IP process, as follows: Four Ethernet subnets (associated with TLAM devices) Four Subnetwork Access Protocol (SNAP) subnets (associated with TLAM devices) Four X.25 subnets (associated with X25AM devices) One loopback driver (used for testing purposes) The total number of subnets on a Tandem system is limited by the number of TCP/IP processes configured on that system. For example, HOST9 shown in Figure 1-11, could have more than one TCP/IP process configured. Section 2, RFC-1006 Subsystem Configuration, describes the configuration of OSI/AS, OSI/TS, TCP/IP and IOP processes. 1 14 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 Changes in the Transport Layer When Using RFC-1006 This section provides an overview of the following features of OSI/TS when using RFC-1006: Transport Layer protocols: OSI transport protocol class 0 is used along with Transmission Control Protocol (TCP). Transport service user data: Exchange of transport user data during connection establishment is supported. Transport expedited data: Transport expedited data service is supported. Larger TPDU Size: A much larger TPDU size is supported. OSI/TS TPDU and TCP/IP transport packet structure: Only six TPDUs are supported when using RFC-1006. TPDUs are encapsulated into the transport packet for transmission across the network. Transport service procedures: Service primitives, mapping between the OSI and TCP/IP services, and the available transport service procedures. Transport Layer Protocols When TCP/IP is the NSP, OSI/TS uses OSI transport protocol class 0, which does not provide error-recovery, error-detection, or multiplexing. However, TCP/IP uses the TCP, which is very similar to the OSI transport protocol class 4. TCP provides errorrecovery, error-detection, and multiplexing, in addition to other services. TCP and OSI Transport Class 4 Compared The following table compares the services provided by the TCP transport protocol and the OSI transport class 4 protocol. Table 1-1. TCP and OSI Transport Class 4 Compared Service TCP/IP Transport OSI Transport Class 4 Addressing 16 bit port number variable TSAP-ID Data transfer streams blocks Datagrams UDP ISO 8602 Disconnect graceful abrupt Error detection checksum checksum Flow control bytes segments Interrupts urgent pointer expedited data Precedence 3 bit IP field 16 TP, IP fields Security 11 byte IP field variable TP, IP fields The end result is that OSI applications using OSI/TS over TCP/IP receive reliable transport service over a TCP/IP network. The fact that the application is connecting over a TCP/IP network is transparent to the application. 107751 Tandem Computers Incorporated 1 15

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 Transport Service User Data When TCP/IP is the NSP process, user data is exchanged during connection establishment. Up to 32 octets of transport service user data can be exchanged during connection establishment in CR-TPDUs and CC-TPDUs. If you use a CONTROL 17 or CONTROL 11 procedure to request or respond to connection establishment, user data cannot be sent in the CR- and CC-TPDUs. If you use a WRITEREAD procedure to request or respond to connection establishment, user data can be sent in the CR- and CC-TPDUs. When X25AM is the NSP process, user data is not exchanged during connection establishment for OSI transport protocol class 0. Transport Expedited Data When TCP/IP is the NSP process, OSI/TS supports transport expedited data transfer service for OSI transport protocol class 0. OSI/TS can use network expedited data transfer service (TCP/IP out-of-band data facility) for Expedited Data (ED) TPDUs. The Tandem RFC-1006 implementation defines the default for the EXPEDITED configuration attribute as OFF. When X25AM or TLAM is the NSP, OSI/TS supports ED-TPDU transfer service for classes OSI transport classes 1, 2, 3, and 4 only. Larger TPDU Size When TCP/IP is the NSP, OSI/TS supports TPDU sizes up to 65531 octets. Use of a larger TPDU can improve throughout due to decreased numbers of interprocess communication (IPC) messages. When X25AM or TLAM is the NSP, OSI/TS supports a TPDU size up to 8192 octets for OSI transport classes 1, 2, 3, and 4 and supports up to 2048 octets for class 0. TPDU and Transport Packet Structure Table 1-2 lists the six TPDUs used by OSI/TS when it is using RFC-1006. Table 1-2. TPDUs Used by RFC-1006 TPDU Function CR-TPDU During connection establishment, used to request a transport connection and to exchange user data CC-TPDU During connection establishment, used to confirm a CR-TPDU and to exchange user data DT-TPDU During data transfer, used to transfer user data ED-TPDU * During data transfer, used to transfer expedited user data DR-TPDU During connection release, used to request a connection release ER-TPDU Used to convey error information *Normally the ED-TPDU is not provided for OSI transport protocol class 0, but it is included when using RFC-1006. 1 16 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 The following TPDUs are not used by OSI/TS when using RFC-1006: AK-TPDU EA-TPDU RJ-TPDU DC-TPDU Note RFC983 is an earlier version of a protocol for connecting ISO transport services on top of the TCP, and it was superseded by the RFC1006 standard. If you are connecting to a system that has implemented RFC983, there are differences in the transport services between RFC983 and RFC-1006 that may have to be resolved before connections can be successfully made. For example, in RFC983, under Item 6, Packet Format, ER-TPDUs are not supported and the source and destination reference bits in the CR- and CC-TPDUs are either set to 0 or ignored, but the Tandem implementation of RFC-1006 uses ER-TPDUs, and places information in the source and destination reference bits. Encapsulation of TPDU Into the Transport Packet Transport Packet Format and Length The OSI TPDU is encapsulated by OSI/TS into a transport packet as specified by the RFC 1006 standard. This is shown in Figure 1-12. Data is transmitted from a transport service entity (through TCP/IP, over the network) to the peer entity in a transport packet. A transport packet consists of two parts: 4 bytes of packet header to identify the RFC-1006 protocol, and the TPDU. Figure 1-12 illustrates the transport packet. Figure 1-12. Transport Packet Octet 1 2 3, 4 5-p Version Reserved Packet Length TPDU Header User Data Transport Packet Header TPDU Transport Packet 055 107751 Tandem Computers Incorporated 1 17

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 Transport Packet Header TPDU This field contains the following three fields: Version This field is 8 bits long. It has the value of 3, which represents Version 3 of the RFC 1006 standard. Reserved This field is unused. Packet Length This field is 16 bits long. It indicates the length of entire TCP transport packet, in octets. This length is the length of the transport packet header (4 octets) plus the length of the TPDU. The TPDU contains two parts: TPDU Header and (optionally) User Data. See Section 5, TPDUs Used by RFC-1006, for detailed information on the TPDUs used by RFC-1006. This information might be useful when you are looking at trace records. Service Primitives This section contains five tables describing the service primitives. The first three define OSI service primitives (Transport and Network Layers) and TCP service primitives. The last two tables show the mapping of the OSI primitives and parameters to the TCP primitives and parameters. OSI Transport Service Primitives The OSI Transport Layer provides the following OSI transport service primitives to the transport service user, as defined in ISO 8072, with the exception of a T-ATTACH, which is a Tandem-specific primitive. Table 1-3 describes the transport service primitives. 1 18 107751 Tandem Computers Incorporated

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 Table 1-3. OSI Transport Service Primitives Connection Establishment Primitive T-CONNECT.REQUEST T-ATTACH * T-CONNECT.INDICATION T-CONNECT.RESPONSE T-CONNECT.CONFIRMATION Function A calling transport service user indicates that it wants to establish a connection. A called transport service user indicates that it is waiting for an incoming connection. A called transport service user is notified that connection establishment is in progress. A called transport service user indicates that it will honor the request. A calling transport service user is notified that the connection has been established. Data Transfer Primitive T-DATA.REQUEST T-DATA.INDICATION T-EXPEDITED DATA.REQUEST T-EXPEDITED DATA.INDICATION Function A sending transport service user sends data. A receiving transport service user is notified that data can be read from the connection. A sending transport service user sends expedited data. A receiving transport service user is notified that expedited data can be read from the connection. Primitive T-DISCONNECT.REQUEST Connection Release Function A transport service user indicates that the connection is to be closed. T-DISCONNECT.INDICATION A transport service user is notified that the connection is closed. * This transport service primitive is Tandem-specific, not defined in ISO 8072. 107751 Tandem Computers Incorporated 1 19

Introduction to RFC-1006 Changes in the Transport Layer When Using RFC-1006 OSI Network Service Primitives The OSI Network Layer provides the following OSI network service primitives, as defined in ISO 8073, to the network service user, with the exception of N-ATTACH, which is a Tandem-specific primitive. Table 1-4 describes the network Service primitive. Table 1-4. OSI Network Service Primitives Connection Establishment Primitive N-CONNECT.REQUEST N-ATTACH * N-CONNECT.INDICATION N-CONNECT.RESPONSE N-CONNECT.CONFIRMATION Function A calling network service user indicates that it wants to establish a connection. A called network service user indicates that it is waiting for an incoming connection. A called network service user is notified that connection establishment is in progress. A called network service user indicates that it will honor the request. A calling network service user is notified that the connection has been established. Data Transfer Primitive N-DATA.REQUEST N-DATA.INDICATION Function A sending network service user sends data. A receiving network service user is notified that data can be read from the connection. Connection Release Primitive N-DISCONNECT.REQUEST N-DISCONNECT.INDICATION Function A network service user indicates that the connection is to be closed. A network service user is notified that the connection is closed. Primitive N-RESET.INDICATION ** Connection Reset Function A network service user is notified that the connection is reset. * This network service primitive is Tandem-specific, not defined in ISO 8073. * * An ECONNRESET error code is returned on a socket RECV_NW or SEND_NW call when a TCP connection has been reset. 1 20 107751 Tandem Computers Incorporated