ÉÂÔ TCP/IP Tutorial and Technical Overview Martin W. Murhammer, Orcun Atakan, Stefan Bretz, Larry R. Pugh, Kazunari Suzuki, David H. Wood International Technical Support Organization http://www.redbooks.ibm.com GG24-3376-05 ÉÂÔ International Technical Support Organization GG24-3376-05 TCP/IP Tutorial and Technical Overview October 1998 Take Note! Before using this information and the product it supports, be sure to read the general information in Appendix A, “Special Notices” on page 673. Sixth Edition (October 1998) This edition applies to Transmission Control Protocol/Internet Protocol (TCP/IP) in general and selected IBM and OEM implementations thereof. Comments may be addressed to: IBM Corporation, International Technical Support Organization Dept. HZ8 Building 678 P.O. Box 12195 Research Triangle Park, NC 27709-2195 When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believes appropriate without incurring any obligation to you. Copyright International Business Machines Corporation 1989, 1998. All rights reserved. Note to U.S. Government Users — Documentation related to restricted rights — Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp. Contents Preface . xiii The Team That Wrote This Redbook ........................ xiii Comments Welcome . xv Part 1. Architecture and Core Protocols ............................. 1 Chapter 1. Introduction to TCP/IP - History, Architecture and Standards . 3 1.1 Internet History - Where It All Came From ................... 3 1.1.1 Internetworks . 4 1.1.2 The Internet . 4 1.1.3 ARPANET . 5 1.1.4 NSFNET . 5 1.1.5 Commercial Use of the Internet ....................... 7 1.1.6 Information Superhighway . 8 1.1.7 Internet2 . 9 1.1.8 The Open Systems Interconnect (OSI) Model ............... 9 1.2 TCP/IP Architectural Model - What It Is All About .............. 11 1.2.1 Internetworking . 11 1.2.2 The TCP/IP Protocol Stack ......................... 12 1.2.3 TCP/IP Applications . 14 1.2.4 Bridges, Routers and Gateways ...................... 15 1.3 Finding Standards for TCP/IP and the Internet ................ 17 1.3.1 Request For Comments (RFC) ...................... 18 1.3.2 Internet Standards . 19 1.3.3 Major Internet Protocols .......................... 20 1.4 Future of the Internet ............................... 21 1.5 IBM and the Internet ............................... 22 1.5.1 The Network Computing Framework ................... 22 Chapter 2. Internetworking and Transport Layer Protocols ......... 27 2.1 Internet Protocol (IP) ............................... 27 2.1.1 IP Addressing . 27 2.1.2 IP Subnets . 30 2.1.3 IP Routing . 35 2.1.4 Methods of Delivery - Unicast, Broadcast, Multicast and Anycast .. 39 2.1.5 The IP Address Exhaustion Problem ................... 42 2.1.6 Intranets (Private IP Addresses) ...................... 44 2.1.7 Classless Inter-Domain Routing (CIDR) ................. 45 2.1.8 IP Datagram . 48 2.2 Internet Control Message Protocol (ICMP) .................. 58 2.2.1 ICMP Messages . 59 2.2.2 ICMP Applications . 66 2.3 Internet Group Management Protocol (IGMP) ................. 67 2.4 Address Resolution Protocol (ARP) ...................... 68 2.4.1 ARP Overview . 68 2.4.2 ARP Detailed Concept ........................... 68 2.4.3 ARP and Subnets .............................. 71 2.4.4 Proxy-ARP or Transparent Subnetting .................. 71 2.5 Reverse Address Resolution Protocol (RARP) ................ 72 Copyright IBM Corp. 1989, 1998 iii 2.5.1 RARP Concept . 72 2.6 Ports and Sockets ................................ 73 2.6.1 Ports . 73 2.6.2 Sockets . 74 2.7 User Datagram Protocol (UDP) ......................... 75 2.7.1 UDP Datagram Format ........................... 76 2.7.2 UDP Application Programming Interface ................. 77 2.8 Transmission Control Protocol (TCP) ..................... 78 2.8.1 TCP Concept . 78 2.8.2 TCP Application Programming Interface ................. 88 2.8.3 TCP Congestion Control Algorithms ................... 88 2.9 References . 93 Chapter 3. Routing Protocols . 95 3.1 Basic IP Routing ................................. 95 3.1.1 Routing Processes . 97 3.1.2 Autonomous Systems . 97 3.2 Routing Algorithms . 98 3.2.1 Static Routing . 98 3.2.2 Distance Vector Routing .......................... 99 3.2.3 Link State Routing ............................. 104 3.3 Interior Gateway Protocols (IGP) ....................... 106 3.3.1 Routing Information Protocol (RIP) ................... 106 3.3.2 Routing Information Protocol Version 2 (RIP-2) ............ 108 3.3.3 RIPng for IPv6 ............................... 110 3.3.4 Open Shortest Path First (OSPF) .................... 112 3.4 Exterior Routing Protocols ........................... 134 3.4.1 Exterior Gateway Protocol (EGP) .................... 134 3.4.2 Border Gateway Protocol (BGP-4) ................... 135 3.5 References . 147 Chapter 4. Application Protocols . 149 4.1 Characteristics of Applications ........................ 149 4.1.1 Client/Server Model . 149 4.2 Domain Name System (DNS) ......................... 150 4.2.1 The Hierarchical Namespace ...................... 151 4.2.2 Fully Qualified Domain Names (FQDNs) ................ 151 4.2.3 Generic Domains . 152 4.2.4 Country Domains . 152 4.2.5 Mapping Domain Names to IP Addresses ............... 153 4.2.6 Mapping IP Addresses to Domain Names — Pointer Queries .... 153 4.2.7 The Distributed Name Space ...................... 153 4.2.8 Domain Name Resolution ........................ 154 4.2.9 Domain Name System Resource Records ............... 157 4.2.10 Domain Name System Messages ................... 159 4.2.11 A Simple Scenario ............................ 163 4.2.12 Extended Scenario . 165 4.2.13 Transport . 165 4.2.14 DNS Applications . 166 4.2.15 References . 167 4.3 TELNET . 167 4.3.1 TELNET Operation . 167 4.3.2 Terminal Emulation (Telnet 3270) .................... 172 4.3.3 TN3270 Enhancements (TN3270E) ................... 173 iv TCP/IP Tutorial and Technical Overview 4.3.4 References . 175 4.4 File Transfer Protocol (FTP) .......................... 175 4.4.1 Overview of FTP .............................. 175 4.4.2 FTP Operations . 176 4.4.3 Reply Codes . 178 4.4.4 FTP Scenario . 179 4.4.5 A Sample FTP Session .......................... 179 4.4.6 Anonymous FTP . 180 4.4.7 Remote Job Entry Using FTP ...................... 180 4.5 Trivial File Transfer Protocol (TFTP) ..................... 180 4.5.1 TFTP Usage . 181 4.5.2 Protocol Description . 181 4.5.3 TFTP Multicast Option .......................... 182 4.5.4 Security Issue . 183 4.6 Remote Execution Command Protocol (REXEC and RSH) ........ 183 4.6.1 Principle of Operation ........................... 183 4.7 Simple Mail Transfer Protocol (SMTP) .................... 184 4.7.1 How SMTP Works ............................. 186 4.7.2 SMTP and the Domain Name System ................. 191 4.7.3 References . 193 4.8 Multipurpose Internet Mail Extensions (MIME) ............... 193 4.8.1 How MIME Works ............................. 196 4.8.2 The Content-Type Field .......................... 196 4.8.3 The Content-Transfer-Encoding Field .................. 202 4.8.4 Using Non-ASCII Characters in Message Headers .......... 206 4.8.5 References . 207 4.9 Post Office Protocol (POP) .......................... 208 4.9.1 POP3 Commands and Responses ................... 208 4.9.2 References . 209 4.10 Internet Message Access Protocol Version 4 (IMAP4) .......... 209 4.10.1 IMAP4 Underlying Electronic Mail Models .............. 210 4.10.2 IMAP4 Commands and Responses .................. 210 4.10.3 Message Numbers . 211 4.10.4 IMAP4 States . 212 4.10.5 Client Commands . 213 4.10.6 References . 214 4.11 Network Management . 214 4.11.1 Standards . 215 4.11.2 Bootstrap Protocol (BOOTP) ...................... 215 4.11.3 Structure and Identification of Management Information (SMI) ... 215 4.11.4 Management Information Base (MIB) ................. 216 4.11.5 Simple Network Management Protocol (SNMP) ........... 220 4.11.6 Simple Network Management Protocol Version 2 (SNMPv2) ... 222 4.11.7 MIB for SNMPv2 ............................. 225 4.11.8 Single Authentication and Privacy Protocol .............. 226 4.11.9 The New Administrative Model ..................... 227 4.11.10 Simple Network Management Protocol Version 3 (SNMPv3) ... 228 4.11.11 References . 229 4.12 Remote Printing (LPR and LPD) ...................... 230 4.13 Network File System (NFS) ......................... 230 4.13.1 NFS Concept . 230 4.13.2 WebNFS . 234 4.13.3 References . 235 4.14 X Window System ............................... 235 Contents v 4.14.1 Functional Concept . 236 4.14.2 Protocol . 239 4.15 Finger Protocol . 240 4.16 NETSTAT . 240 4.17 Network Information System (NIS) ..................... 241 4.18 NetBIOS over TCP/IP ............................. 241 4.18.1 NetBIOS over TCP/IP in IBM OS/2 Warp 4 ............. 244 4.18.2 NetBIOS over TCP/IP in Microsoft Windows Systems ....... 245 4.18.3 NetBIOS Name Server (NBNS) Implementations .......... 247 4.19 Application Programming Interfaces (APIs) ................ 248 4.19.1 The Socket API .............................. 248 4.19.2 Remote Procedure Call (RPC) ..................... 252 4.19.3 Windows Sockets Version 2 (Winsock V2.0) ............. 256 4.19.4 SNMP Distributed Programming Interface (SNMP DPI) ....... 257 4.19.5 FTP API . 259 4.19.6 CICS Socket Interface .......................... 260 4.19.7 IMS Socket Interface .........................