TCP/IP Tutorial and Technical Overview - … · 5.9 Border Gateway Protocol (BGP) ... 6.5.1 Protocol overview ... 6.8.2 Border Gateway Multicast Protocol

ibm.com/redbooks

TCP/IP Tutorial and Technical Overview

Lydia ParzialeDavid T. BrittChuck Davis

Jason ForresterWei Liu

Carolyn MatthewsNicolas Rosselot

Understand networking fundamentals of the TCP/IP protocol suite

Introduces advanced concepts and new technologies

Includes the latest TCP/IP protocols

Front cover

http://www.redbooks.ibm.com/http://www.redbooks.ibm.com/

TCP/IP Tutorial and Technical Overview

December 2006

International Technical Support Organization

GG24-3376-07

Copyright International Business Machines Corporation 1989-2006. All rights reserved.Note to U.S. Government Users Restricted Rights -- Use, duplication or disclosure restricted by GSA ADPSchedule Contract with IBM Corp.

Eighth Edition (December 2006)

Note: Before using this information and the product it supports, read the information in Notices on page xvii.

Contents

Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviiTrademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xixThe team that wrote this redbook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxBecome a published author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiiComments welcome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii

Part 1. Core TCP/IP protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Chapter 1. Architecture, history, standards, and trends . . . . . . . . . . . . . . . 31.1 TCP/IP architectural model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.1.1 Internetworking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.1.2 The TCP/IP protocol layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.1.3 TCP/IP applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.2 The roots of the Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.2.1 ARPANET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.2.2 NSFNET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.2.3 Commercial use of the Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161.2.4 Internet2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181.2.5 The Open Systems Interconnection (OSI) Reference Model . . . . . . 20

1.3 TCP/IP standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211.3.1 Request for Comments (RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221.3.2 Internet standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

1.4 Future of the Internet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261.4.1 Multimedia applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261.4.2 Commercial use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261.4.3 The wireless Internet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1.5 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Chapter 2. Network interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292.1 Ethernet and IEEE 802 local area networks (LANs) . . . . . . . . . . . . . . . . . 30

2.1.1 Gigabit Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.2 Fiber Distributed Data Interface (FDDI). . . . . . . . . . . . . . . . . . . . . . . . . . . 332.3 Serial Line IP (SLIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342.4 Point-to-Point Protocol (PPP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2.4.1 Point-to-point encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.5 Integrated Services Digital Network (ISDN) . . . . . . . . . . . . . . . . . . . . . . . 382.6 X.25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Copyright IBM Corp. 1989-2006. All rights reserved. iii

2.7 Frame relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.7.1 Frame format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.7.2 Interconnect issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432.7.3 Data link layer parameter negotiation . . . . . . . . . . . . . . . . . . . . . . . . 432.7.4 IP over frame relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

2.8 PPP over SONET and SDH circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452.8.1 Physical layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2.9 Multi-Path Channel+ (MPC+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462.10 Asynchronous transfer mode (ATM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

2.10.1 Address resolution (ATMARP and InATMARP) . . . . . . . . . . . . . . . 472.10.2 Classical IP over ATM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502.10.3 ATM LAN emulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562.10.4 Classical IP over ATM versus LAN emulation. . . . . . . . . . . . . . . . . 59

2.11 Multiprotocol over ATM (MPOA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.11.1 Benefits of MPOA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.11.2 MPOA logical components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612.11.3 MPOA functional components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622.11.4 MPOA operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

2.12 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Chapter 3. Internetworking protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673.1 Internet Protocol (IP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

3.1.1 IP addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683.1.2 IP subnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723.1.3 IP routing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773.1.4 Methods of delivery: Unicast, broadcast, multicast, and anycast . . . 843.1.5 The IP address exhaustion problem . . . . . . . . . . . . . . . . . . . . . . . . . 863.1.6 Intranets: Private IP addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893.1.7 Network Address Translation (NAT) . . . . . . . . . . . . . . . . . . . . . . . . . 893.1.8 Classless Inter-Domain Routing (CIDR) . . . . . . . . . . . . . . . . . . . . . . 953.1.9 IP datagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

3.2 Internet Control Message Protocol (ICMP) . . . . . . . . . . . . . . . . . . . . . . . 1093.2.1 ICMP messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103.2.2 ICMP applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

3.3 Internet Group Management Protocol (IGMP) . . . . . . . . . . . . . . . . . . . . 1193.4 Address Resolution Protocol (ARP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

3.4.1 ARP overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1193.4.2 ARP detailed concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203.4.3 ARP and subnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233.4.4 Proxy-ARP or transparent subnetting . . . . . . . . . . . . . . . . . . . . . . . 123

3.5 Reverse Address Resolution Protocol (RARP) . . . . . . . . . . . . . . . . . . . . 1243.5.1 RARP concept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

3.6 Bootstrap Protocol (BOOTP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

iv TCP/IP Tutorial and Technical Overview

3.6.1 BOOTP forwarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293.6.2 BOOTP considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

3.7 Dynamic Host Configuration Protocol (DHCP) . . . . . . . . . . . . . . . . . . . . 1303.7.1 The DHCP message format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1323.7.2 DHCP message types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1343.7.3 Allocating a new network address. . . . . . . . . . . . . . . . . . . . . . . . . . 1343.7.4 DHCP lease renewal process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1373.7.5 Reusing a previously allocated network address . . . . . . . . . . . . . . 1383.7.6 Configuration parameters repository. . . . . . . . . . . . . . . . . . . . . . . . 1393.7.7 DHCP considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1393.7.8 BOOTP and DHCP interoperability . . . . . . . . . . . . . . . . . . . . . . . . . 140


Chapter 4. Transport layer protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1434.1 Ports and sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

4.1.1 Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1444.1.2 Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

4.2 User Datagram Protocol (UDP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1464.2.1 UDP datagram format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1474.2.2 UDP application programming interface . . . . . . . . . . . . . . . . . . . . . 149

4.3 Transmission Control Protocol (TCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494.3.1 TCP concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1504.3.2 TCP application programming interface . . . . . . . . . . . . . . . . . . . . . 1644.3.3 TCP congestion control algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 165


Chapter 5. Routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1715.1 Autonomous systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1735.2 Types of IP routing and IP routing algorithms . . . . . . . . . . . . . . . . . . . . . 174

5.2.1 Static routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1755.2.2 Distance vector routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1765.2.3 Link state routing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1775.2.4 Path vector routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1785.2.5 Hybrid routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

5.3 Routing Information Protocol (RIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1805.3.1 RIP packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1805.3.2 RIP packet format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1815.3.3 RIP modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1825.3.4 Calculating distance vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1825.3.5 Convergence and counting to infinity . . . . . . . . . . . . . . . . . . . . . . . 1855.3.6 RIP limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

5.4 Routing Information Protocol Version 2 (RIP-2) . . . . . . . . . . . . . . . . . . . 1895.4.1 RIP-2 packet format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Contents v

5.4.2 RIP-2 limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1925.5 RIPng for IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

5.5.1 Differences between RIPng and RIP-2 . . . . . . . . . . . . . . . . . . . . . . 1935.5.2 RIPng packet format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

5.6 Open Shortest Path First (OSPF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1965.6.1 OSPF terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1965.6.2 Neighbor communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2055.6.3 OSPF neighbor state machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2065.6.4 OSPF route redistribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2085.6.5 OSPF stub areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2105.6.6 OSPF route summarization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

5.7 Enhanced Interior Gateway Routing Protocol (EIGRP). . . . . . . . . . . . . . 2125.7.1 Features of EIGRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2125.7.2 EIGRP packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

5.8 Exterior Gateway Protocol (EGP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2155.9 Border Gateway Protocol (BGP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

5.9.1 BGP concepts and terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2165.9.2 IBGP and EBGP communication . . . . . . . . . . . . . . . . . . . . . . . . . . 2185.9.3 Protocol description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2205.9.4 Path selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2235.9.5 BGP synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2265.9.6 BGP aggregation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2285.9.7 BGP confederations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2305.9.8 BGP route reflectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

5.10 Routing protocol selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2335.11 Additional functions performed by the router. . . . . . . . . . . . . . . . . . . . . 2345.12 Routing processes in UNIX-based systems . . . . . . . . . . . . . . . . . . . . . 2355.13 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Chapter 6. IP multicast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2376.1 Multicast addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

6.1.1 Multicasting on a single physical network . . . . . . . . . . . . . . . . . . . . 2386.1.2 Multicasting between network segments . . . . . . . . . . . . . . . . . . . . 240

6.2 Internet Group Management Protocol (IGMP) . . . . . . . . . . . . . . . . . . . . 2416.2.1 IGMP messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2416.2.2 IGMP operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

6.3 Multicast delivery tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2506.4 Multicast forwarding algorithms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

6.4.1 Reverse path forwarding algorithm . . . . . . . . . . . . . . . . . . . . . . . . . 2526.4.2 Center-based tree algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2536.4.3 Multicast routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

6.5 Distance Vector Multicast Routing Protocol (DVMRP) . . . . . . . . . . . . . . 2546.5.1 Protocol overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

vi TCP/IP Tutorial and Technical Overview

6.5.2 Building and maintaining multicast delivery trees . . . . . . . . . . . . . . 2566.5.3 DVMRP tunnels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

6.6 Multicast OSPF (MOSPF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2586.6.1 Protocol overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2596.6.2 MOSPF and multiple OSPF areas . . . . . . . . . . . . . . . . . . . . . . . . . 2606.6.3 MOSPF and multiple autonomous systems . . . . . . . . . . . . . . . . . . 2606.6.4 MOSPF interoperability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

6.7 Protocol Independent Multicast (PIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2616.7.1 PIM dense mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2626.7.2 PIM sparse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

6.8 Interconnecting multicast domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2666.8.1 Multicast Source Discovery Protocol (MSDP). . . . . . . . . . . . . . . . . 2666.8.2 Border Gateway Multicast Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 269

6.9 The multicast backbone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2696.9.1 MBONE routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2706.9.2 Multicast applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

6.10 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Chapter 7. Mobile IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2757.1 Mobile IP overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

7.1.1 Mobile IP operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2777.1.2 Mobility agent advertisement extensions . . . . . . . . . . . . . . . . . . . . 278

7.2 Mobile IP registration process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2807.2.1 Tunneling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2847.2.2 Broadcast datagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2847.2.3 Move detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2847.2.4 Returning home. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2857.2.5 ARP considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2857.2.6 Mobile IP security considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 286


Chapter 8. Quality of service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2878.1 Why QoS? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2888.2 Integrated Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

8.2.1 Service classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2928.2.2 Controlled Load Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2948.2.3 Guaranteed Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2958.2.4 The Resource Reservation Protocol (RSVP) . . . . . . . . . . . . . . . . . 2968.2.5 Integrated Services outlook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

8.3 Differentiated Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3098.3.1 Differentiated Services architecture . . . . . . . . . . . . . . . . . . . . . . . . 3108.3.2 Organization of the DSCP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3138.3.3 Configuration and administration of DS with LDAP. . . . . . . . . . . . . 322

Contents vii


Chapter 9. IP version 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3279.1 IPv6 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

9.1.1 IP growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3289.1.2 IPv6 feature overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

9.2 The IPv6 header format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3309.2.1 Extension headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3339.2.2 IPv6 addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3399.2.3 Traffic class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3459.2.4 Flow labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3469.2.5 IPv6 security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3479.2.6 Packet sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350

9.3 Internet Control Message Protocol Version 6 (ICMPv6) . . . . . . . . . . . . . 3529.3.1 Neighbor discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3539.3.2 Multicast Listener Discovery (MLD) . . . . . . . . . . . . . . . . . . . . . . . . 365

9.4 DNS in IPv6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3679.4.1 Format of IPv6 resource records. . . . . . . . . . . . . . . . . . . . . . . . . . . 368

9.5 DHCP in IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3719.5.1 DHCPv6 messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

9.6 IPv6 mobility support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3729.7 IPv6 new opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

9.7.1 New infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3769.7.2 New services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3779.7.3 New research and development platforms . . . . . . . . . . . . . . . . . . . 378

9.8 Internet transition: Migrating from IPv4 to IPv6 . . . . . . . . . . . . . . . . . . . . 3799.8.1 Dual IP stack implementation: The IPv6/IPv4 node . . . . . . . . . . . . 3809.8.2 Tunneling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3819.8.3 Interoperability summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388


Chapter 10. Wireless IP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39110.1 Wireless concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39210.2 Why wireless? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

10.2.1 Deployment and cost effectiveness . . . . . . . . . . . . . . . . . . . . . . . 39510.2.2 Reachability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39610.2.3 Scalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39610.2.4 Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39710.2.5 Connectivity and reliability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

10.3 WiFi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39710.4 WiMax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40010.5 Applications of wireless networking. . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

10.5.1 Last mile connectivity in broadband services . . . . . . . . . . . . . . . . 402

viii TCP/IP Tutorial and Technical Overview

10.5.2 Hotspots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40210.5.3 Mesh networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

10.6 IEEE standards relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . 403

Part 2. TCP/IP application protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405

Chapter 11. Application structure and programming interfaces . . . . . . 40711.1 Characteristics of applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

11.1.1 The client/server model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40811.2 Application programming interfaces (APIs) . . . . . . . . . . . . . . . . . . . . . . 410

11.2.1 The socket API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41011.2.2 Remote Procedure Call (RPC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 41511.2.3 The SNMP distributed programming interface (SNMP DPI) . . . . . 41911.2.4 REXX sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422


Chapter 12. Directory and naming protocols . . . . . . . . . . . . . . . . . . . . . . 42512.1 Domain Name System (DNS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426

12.1.1 The hierarchical namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42612.1.2 Fully qualified domain names (FQDNs) . . . . . . . . . . . . . . . . . . . . 42812.1.3 Generic domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42812.1.4 Country domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42912.1.5 Mapping domain names to IP addresses . . . . . . . . . . . . . . . . . . . 42912.1.6 Mapping IP addresses to domain names: Pointer queries . . . . . . 43012.1.7 The distributed name space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43012.1.8 Domain name resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43212.1.9 Domain Name System resource records . . . . . . . . . . . . . . . . . . . 43612.1.10 Domain Name System messages. . . . . . . . . . . . . . . . . . . . . . . . 43912.1.11 A simple scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44512.1.12 Extended scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44912.1.13 Transport. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45012.1.14 DNS applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

12.2 Dynamic Domain Name System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45312.2.1 Dynamic updates in the DDNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 45412.2.2 Incremental zone transfers in DDNS. . . . . . . . . . . . . . . . . . . . . . . 45612.2.3 Prompt notification of zone transfer . . . . . . . . . . . . . . . . . . . . . . . 457

12.3 Network Information System (NIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45812.4 Lightweight Directory Access Protocol (LDAP) . . . . . . . . . . . . . . . . . . . 459

12.4.1 LDAP: Lightweight access to X.500 . . . . . . . . . . . . . . . . . . . . . . . 46012.4.2 The LDAP directory server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46112.4.3 Overview of LDAP architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . 46312.4.4 LDAP models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46412.4.5 LDAP security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47112.4.6 LDAP URLs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474

Contents ix

12.4.7 LDAP and DCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47512.4.8 The Directory-Enabled Networks (DEN) initiative . . . . . . . . . . . . . 47712.4.9 Web-Based Enterprise Management (WBEM) . . . . . . . . . . . . . . . 478


Chapter 13. Remote execution and distributed computing. . . . . . . . . . . 48313.1 Telnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

13.1.1 Telnet operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48413.1.2 Network Virtual Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48513.1.3 Telnet options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48713.1.4 Telnet command structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48913.1.5 Option negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49113.1.6 Telnet basic commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49213.1.7 Terminal emulation (Telnet 3270) . . . . . . . . . . . . . . . . . . . . . . . . . 49213.1.8 TN3270 enhancements (TN3270E) . . . . . . . . . . . . . . . . . . . . . . . 49313.1.9 Device-type negotiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

13.2 Remote Execution Command protocol (REXEC and RSH) . . . . . . . . . 49513.3 Introduction to the Distributed Computing Environment (DCE). . . . . . . 496

13.3.1 DCE directory service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49813.3.2 Authentication service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50213.3.3 DCE threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50513.3.4 Distributed Time Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50713.3.5 Additional information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

13.4 Distributed File Service (DFS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50913.4.1 File naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51013.4.2 DFS performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511


Chapter 14. File-related protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51314.1 File Transfer Protocol (FTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

14.1.1 An overview of FTP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51414.1.2 FTP operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51514.1.3 The active data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52014.1.4 The passive data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52114.1.5 Using proxy transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52214.1.6 Reply codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52314.1.7 Anonymous FTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52514.1.8 Using FTP with IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52514.1.9 Securing FTP sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527

14.2 Trivial File Transfer Protocol (TFTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . 52914.2.1 TFTP usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53014.2.2 Protocol description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53114.2.3 TFTP packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

x TCP/IP Tutorial and Technical Overview

14.2.4 Data modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53214.2.5 TFTP multicast option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53214.2.6 Security issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533

14.3 Secure Copy Protocol (SCP) and SSH FTP (SFTP). . . . . . . . . . . . . . . 53314.3.1 SCP syntax and usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53314.3.2 SFTP syntax and usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53514.3.3 SFTP interactive commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536

14.4 Network File System (NFS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53814.4.1 NFS concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53814.4.2 File integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54214.4.3 Lock Manager protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54314.4.4 NFS file system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54314.4.5 NFS version 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54314.4.6 Cache File System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54514.4.7 WebNFS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545

14.5 The Andrew File System (AFS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54614.6 Common Internet File System (CIFS) . . . . . . . . . . . . . . . . . . . . . . . . . . 548

14.6.1 NetBIOS over TCP/IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54814.6.2 SMB/CIFS specifics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550


Chapter 15. Mail applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55515.1 Simple Mail Transfer Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

15.1.1 How SMTP works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55915.1.2 SMTP and the Domain Name System . . . . . . . . . . . . . . . . . . . . . 565

15.2 Sendmail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56815.2.1 Sendmail as a mail transfer agent (MTA) . . . . . . . . . . . . . . . . . . . 56815.2.2 How sendmail works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

15.3 Multipurpose Internet Mail Extensions (MIME) . . . . . . . . . . . . . . . . . . . 57115.3.1 How MIME works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57415.3.2 The Content-Transfer-Encoding field . . . . . . . . . . . . . . . . . . . . . . 58215.3.3 Using non-ASCII characters in message headers . . . . . . . . . . . . 587

15.4 Post Office Protocol (POP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58915.4.1 Connection states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58915.4.2 POP3 commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . 590

15.5 Internet Message Access Protocol (IMAP4) . . . . . . . . . . . . . . . . . . . . . 59115.5.1 Fundamental IMAP4 electronic mail models. . . . . . . . . . . . . . . . . 59115.5.2 IMAP4 states. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59215.5.3 IMAP4 commands and response interaction . . . . . . . . . . . . . . . . 59415.5.4 IMAP4 messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597


Chapter 16. The Web . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601

Contents xi

16.1 Web browsers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60316.2 Web servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60416.3 Hypertext Transfer Protocol (HTTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . 605

16.3.1 Overview of HTTP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60516.3.2 HTTP operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606

16.4 Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61516.4.1 Static content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61516.4.2 Client-side dynamic content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61616.4.3 Server-side dynamic content. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61716.4.4 Developing content with IBM Web application servers . . . . . . . . . 621


Chapter 17. Network management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62317.1 The Simple Network Management Protocol (SNMP) . . . . . . . . . . . . . . 624

17.1.1 The Management Information Base (MIB) . . . . . . . . . . . . . . . . . . 62517.1.2 The SNMP agent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63017.1.3 The SNMP manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63117.1.4 The SNMP subagent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63217.1.5 The SNMP model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63317.1.6 SNMP traps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63817.1.7 SNMP versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63917.1.8 Single authentication and privacy protocol . . . . . . . . . . . . . . . . . . 647

17.2 The NETSTAT utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64817.2.1 Common NETSTAT options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64917.2.2 Sample NETSTAT report output . . . . . . . . . . . . . . . . . . . . . . . . . . 649


Chapter 18. Wireless Application Protocol . . . . . . . . . . . . . . . . . . . . . . . . 65518.1 The WAP environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65718.2 Key elements of the WAP specifications. . . . . . . . . . . . . . . . . . . . . . . . 65718.3 WAP architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65818.4 Client identifiers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66318.5 Multimedia messaging system (MMS) . . . . . . . . . . . . . . . . . . . . . . . . . 66318.6 WAP push architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664

18.6.1 Push framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66418.6.2 Push proxy gateway (PPG). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66518.6.3 Push access control protocol (PAP) . . . . . . . . . . . . . . . . . . . . . . . 66718.6.4 Service indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66818.6.5 Push over-the-air protocol (OTA) . . . . . . . . . . . . . . . . . . . . . . . . . 66818.6.6 Client-side infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66818.6.7 Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669

18.7 The Wireless Application Environment (WAE2) . . . . . . . . . . . . . . . . . . 67018.8 User Agent Profile (UAProf) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

xii TCP/IP Tutorial and Technical Overview

18.9 Wireless protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67218.9.1 Wireless Datagram Protocol (WDP) . . . . . . . . . . . . . . . . . . . . . . . 67218.9.2 Wireless Profiled Transmission Control Protocol (WP-TCP) . . . . 67418.9.3 Wireless Control Message Protocol (WCMP) . . . . . . . . . . . . . . . . 67818.9.4 Wireless Transaction Protocol (WTP) . . . . . . . . . . . . . . . . . . . . . . 67918.9.5 Wireless Session Protocol (WSP). . . . . . . . . . . . . . . . . . . . . . . . . 68218.9.6 Wireless profiled HTTP (W-HTTP) . . . . . . . . . . . . . . . . . . . . . . . . 695

18.10 Wireless security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69618.10.1 Wireless Transport Layer Security (WTLS). . . . . . . . . . . . . . . . . 69618.10.2 Wireless Identity Module (WIM) . . . . . . . . . . . . . . . . . . . . . . . . . 701

18.11 Wireless Telephony Application (WTA). . . . . . . . . . . . . . . . . . . . . . . . 70218.12 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70218.13 Specifications relevant to this chapter. . . . . . . . . . . . . . . . . . . . . . . . . 703

Chapter 19. Presence over IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70719.1 Overview of the presence service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71019.2 Presence Information Data Format (PIDF) . . . . . . . . . . . . . . . . . . . . . . 71419.3 Presence protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716

19.3.1 Binding to TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71819.3.2 Address resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 718


Part 3. Advanced concepts and new technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721

Chapter 20. Voice over Internet Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 72320.1 Voice over IP (VoIP) introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724

20.1.1 Benefits and applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72420.1.2 VoIP functional components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726

20.2 Session Initiation Protocol (SIP) technologies. . . . . . . . . . . . . . . . . . . . 73020.2.1 SIP request and response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73220.2.2 Sample SIP message flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73320.2.3 SIP protocol architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 734

20.3 Media Gateway Control Protocol (MGCP) . . . . . . . . . . . . . . . . . . . . . . 73620.3.1 MGCP architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73720.3.2 MGCP primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737

20.4 Media Gateway Controller (Megaco). . . . . . . . . . . . . . . . . . . . . . . . . . . 73820.4.1 Megaco architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738

20.5 ITU-T recommendation H.323. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73920.5.1 H.323 architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73920.5.2 H.323 protocol stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741

20.6 Summary of VoIP protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74220.7 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743

Chapter 21. Internet Protocol Television. . . . . . . . . . . . . . . . . . . . . . . . . . 745

Contents xiii

21.1 IPTV overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74621.1.1 IPTV requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74721.1.2 Business benefits and applications . . . . . . . . . . . . . . . . . . . . . . . . 749

21.2 Functional components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75021.2.1 Content acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75021.2.2 CODEC (encode and decode) . . . . . . . . . . . . . . . . . . . . . . . . . . . 75021.2.3 Display devices and control gateway . . . . . . . . . . . . . . . . . . . . . . 75121.2.4 IP (TV) transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 752

21.3 IPTV technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75221.3.1 Summary of protocol standards . . . . . . . . . . . . . . . . . . . . . . . . . . 75321.3.2 Stream Control Transmission Protocol . . . . . . . . . . . . . . . . . . . . . 75321.3.3 Session Description Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75421.3.4 Real-Time Transport Protocol (RTP) . . . . . . . . . . . . . . . . . . . . . . 75621.3.5 Real-Time Control Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76221.3.6 Moving Picture Experts Group (MPEG) standards . . . . . . . . . . . . 76721.3.7 H.261. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 769


Chapter 22. TCP/IP security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77122.1 Security exposures and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772

22.1.1 Common attacks against security . . . . . . . . . . . . . . . . . . . . . . . . . 77222.1.2 Solutions to network security problems. . . . . . . . . . . . . . . . . . . . . 77222.1.3 Implementations of security solutions . . . . . . . . . . . . . . . . . . . . . . 77422.1.4 Network security policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776

22.2 A short introduction to cryptography . . . . . . . . . . . . . . . . . . . . . . . . . . . 77722.2.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77722.2.2 Symmetric or secret-key algorithms . . . . . . . . . . . . . . . . . . . . . . . 77922.2.3 Asymmetric or public key algorithms. . . . . . . . . . . . . . . . . . . . . . . 78022.2.4 Hash functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78522.2.5 Digital certificates and certification authorities . . . . . . . . . . . . . . . 79122.2.6 Random-number generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79222.2.7 Export/import restrictions on cryptography . . . . . . . . . . . . . . . . . . 793

22.3 Firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79422.3.1 Firewall concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79522.3.2 Components of a firewall system . . . . . . . . . . . . . . . . . . . . . . . . . 79622.3.3 Types of firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 805

22.4 IP Security Architecture (IPSec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80922.4.1 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81022.4.2 Authentication Header (AH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81322.4.3 Encapsulating Security Payload (ESP) . . . . . . . . . . . . . . . . . . . . . 81722.4.4 Combining IPSec protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82322.4.5 Internet Key Exchange (IKE) protocol . . . . . . . . . . . . . . . . . . . . . . 829

22.5 SOCKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846

xiv TCP/IP Tutorial and Technical Overview

22.5.1 SOCKS Version 5 (SOCKSv5) . . . . . . . . . . . . . . . . . . . . . . . . . . . 84822.6 Secure Shell (1 and 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853

22.6.1 SSH overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85322.7 Secure Sockets Layer (SSL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854

22.7.1 SSL overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85422.7.2 SSL protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856

22.8 Transport Layer Security (TLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86122.9 Secure Multipurpose Internet Mail Extension (S-MIME) . . . . . . . . . . . . 86122.10 Virtual private networks (VPNs) overview . . . . . . . . . . . . . . . . . . . . . . 861

22.10.1 VPN introduction and benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . 86222.11 Kerberos authentication and authorization system . . . . . . . . . . . . . . . 864

22.11.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86522.11.2 Naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86522.11.3 Kerberos authentication process. . . . . . . . . . . . . . . . . . . . . . . . . 86622.11.4 Kerberos database management . . . . . . . . . . . . . . . . . . . . . . . . 87022.11.5 Kerberos Authorization Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 87122.11.6 Kerberos Version 5 enhancements. . . . . . . . . . . . . . . . . . . . . . . 871

22.12 Remote access authentication protocols. . . . . . . . . . . . . . . . . . . . . . . 87222.13 Extensible Authentication Protocol (EAP) . . . . . . . . . . . . . . . . . . . . . . 87422.14 Layer 2 Tunneling Protocol (L2TP) . . . . . . . . . . . . . . . . . . . . . . . . . . . 875

22.14.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87622.14.2 Protocol overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87722.14.3 L2TP security issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879

22.15 Secure Electronic Transaction (SET) . . . . . . . . . . . . . . . . . . . . . . . . . 88022.15.1 SET roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88022.15.2 SET transactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88122.15.3 The SET certificate scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883

22.16 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885

Chapter 23. Port based network access control . . . . . . . . . . . . . . . . . . . 88923.1 Port based network access control (NAC) overview . . . . . . . . . . . . . . . 89023.2 Port based NAC component overview . . . . . . . . . . . . . . . . . . . . . . . . . 89123.3 Port based network access control operation . . . . . . . . . . . . . . . . . . . . 892

23.3.1 Port based network access control functional considerations. . . . 90423.4 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906

Chapter 24. Availability, scalability, and load balancing . . . . . . . . . . . . . 90724.1 Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90924.2 Scalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90924.3 Load balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91024.4 Clustering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91024.5 Virtualization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91224.6 Virtual Router Redundancy Protocol (VRRP) . . . . . . . . . . . . . . . . . . . . 914

Contents xv

24.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91424.6.2 VRRP definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91624.6.3 VRRP overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91624.6.4 Sample configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91824.6.5 VRRP packet format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919

24.7 Round-robin DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92124.8 Alternative solutions to load balancing . . . . . . . . . . . . . . . . . . . . . . . . . 921

24.8.1 Network Address Translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92224.8.2 Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923


Appendix A. Multiprotocol Label Switching . . . . . . . . . . . . . . . . . . . . . . . 925A.1 MPLS: An introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 926

A.1.1 Conventional routing versus MPLS forwarding mode. . . . . . . . . . . 926A.1.2 Benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927A.1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 929

A.2 MPLS network processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 932A.2.1 Label swapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 932A.2.2 Label switched path (LSP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934A.2.3 Label stack and label hierarchies . . . . . . . . . . . . . . . . . . . . . . . . . . 934A.2.4 MPLS stacks in a BGP environment. . . . . . . . . . . . . . . . . . . . . . . . 936A.2.5 Label distribution protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938A.2.6 Stream merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 939

A.3 Emulating Ethernet over MPLS networks . . . . . . . . . . . . . . . . . . . . . . . . 939A.4 Generalized Multiprotocol Label Switching (GMPLS) . . . . . . . . . . . . . . . 941

A.4.1 Benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 941A.4.2 MPLS and GMPLS comparison in OTN environment. . . . . . . . . . . 942A.4.3 How does GMPLS work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943A.4.4 Link Management Protocol (LMP) . . . . . . . . . . . . . . . . . . . . . . . . . 944A.4.5 Signaling for route selection and path setup. . . . . . . . . . . . . . . . . . 947A.4.6 GMPLS considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 949A.4.7 GMPLS examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950

A.5 RFCs relevant to this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

Abbreviations and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

Related publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959IBM Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959Other publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959Online resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959How to get IBM Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961Help from IBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963

xvi TCP/IP Tutorial and Technical Overview

Notices

This information was developed for products and services offered in the U.S.A.

IBM may not offer the products, services, or features discussed in this document in other countries. Consult your local IBM representative for information on the products and services currently available in your area. Any reference to an IBM product, program, or service is not intended to state or imply that only that IBM product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any IBM intellectual property right may be used instead. However, it is the user's responsibility to evaluate and verify the operation of any non-IBM product, program, or service.

IBM may have patents or pending patent applications covering subject matter described in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to: IBM Director of Licensing, IBM Corporation, North Castle Drive, Armonk, NY 10504-1785 U.S.A.

The following paragraph does not apply to the United Kingdom or any other country where such provisions are inconsistent with local law: INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.

This information could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this publication at any time without notice.

Any references in this information to non-IBM Web sites are provided for convenience only and do not in any manner serve as an endorsement of those Web sites. The materials at those Web sites are not part of the materials for this IBM product and use of those Web sites is at your own risk.

IBM may use or distribute any of the information you supply in any way it believes appropriate without incurring any obligation to you.

Information concerning non-IBM products was obtained from the suppliers of those products, their published announcements or other publicly available sources. IBM has not tested those products and cannot confirm the accuracy of performance, compatibility or any other claims related to non-IBM products. Questions on the capabilities of non-IBM products should be addressed to the suppliers of those products.

This information contains examples of data and reports used in daily business operations. To illustrate them as completely as possible, the examples include the names of individuals, companies, brands, and products. All of these names are fictitious and any similarity to the names and addresses used by an actual business enterprise is entirely coincidental.

COPYRIGHT LICENSE:

This information contains sample application programs in source language, which illustrate programming techniques on various operating platforms. You may copy, modify, and distribute these sample programs in any form without payment to IBM, for the purposes of developing, using, marketing or distributing application programs conforming to the application programming interface for the operating platform for which the sample programs are written. These examples have not been thoroughly tested under all conditions. IBM, therefore, cannot guarantee or imply reliability, serviceability, or function of these programs.

Copyright IBM Corp. 1989-2006. All rights reserved. xvii

TrademarksThe following terms are trademarks of the International Business Machines Corporation in the United States, other countries, or both:

1350Advanced Peer-to-Peer NetworkingAIX 5LAIXAS/400CICSdeveloperWorksESCONHiperSockets

IBM Global Networkibm.comIBMIPDSLotus NotesLotusMVSNotesOperating System/2OS/2

OS/390OS/400RACFRedbooks (logo) RedbooksRISC System/6000System/390VTAMWebSpherez/OS

The following terms are trademarks of other companies:

SAP, and SAP logos are trademarks or registered trademarks of SAP AG in Germany and in several other countries.

CacheFS, Enterprise JavaBeans, EJB, IPX, Java, Java Naming and Directory Interface, JavaBeans, JavaScript, JavaServer, JavaServer Pages, JavaSoft, JDBC, JDK, JSP, JVM, J2EE, ONC, Solaris, Sun, Sun Microsystems, WebNFS, and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United States, other countries, or both.

Internet Explorer, Microsoft, MSN, Windows NT, Windows, and the Windows logo are trademarks of Microsoft Corporation in the United States, other countries, or both.

Intel, Intel logo, Intel Inside logo, and Intel Centrino logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States, other countries, or both.

UNIX is a registered trademark of The Open Group in the United States and other countries.

Linux is a trademark of Linus Torvalds in the United States, other countries, or both.

Other company, product, or service names may be trademarks or service marks of others.

xviii TCP/IP Tutorial and Technical Overview

Preface

The TCP/IP protocol suite has become a staple of today's international society and global economy. Continually evolving standards provide a wide and flexible foundation on which an entire infrastructure of applications are built. Through these we can seek entertainment, conduct business, make financial transactions, deliver services, and much, much more.

However, because TCP/IP continues to develop and grow in order to meet the changing needs of our communities, it might sometimes be hard to keep track of new functionality or identify new possibilities. For this reason, the TCP/IP Tutorial and Technical Overview provides not only an introduction to the TCP/IP protocol suite, but also serves as a reference for advanced users seeking to keep their TCP/IP skills aligned with current standards. It is our hope that both the novice and the expert will find useful information in this publication.

In Part I, you will find an introduction to the core concepts and history upon which TCP/IP is founded. Included is an introduction to the history of TCP/IP and an overview of its current architecture. We also provide detailed discussions about the protocols that comprise the suite, and how those protocols are most commonly implemented.

Part II expands on the information provided in Part I, providing general application concepts (such as file sharing) and specific application protocols within those concepts (such as the File Transfer Protocol, or FTP). Additionally, Part II discusses applications that might not be included in the standard TCP/IP suite but, because of their wide use throughout the Internet community, are considered de facto standards.

Finally, Part III addresses new concepts and advanced implementations within the TCP/IP architecture. Of particular note, Part III examines the convergence of many formerly disparate networks and services using IP technology. Conjointly, this section reviews potential dangers of this IP convergence and approaches the ever-growing standards used to secure and control access to networks and networked resources.

We purposely kept this book platform independent. However, we recognize that you might have a need to learn more about TCP/IP on various platforms, so the following Web sites might assist you in further researching this topic:

TCP/IP and System z:

http://www.ibm.com/servers/eserver/zseries/zos/bkserv/

Copyright IBM Corp. 1989-2006. All rights reserved. xix

http://www.ibm.com/servers/eserver/zseries/zos/bkserv/

TCP/IP and System p:

http://www.ibm.com/systems/p/library/index.html

TCP/IP and System i:

http://www.ibm.com/servers/eserver/iseries/tcpip/index.html

TCP/IP and System x:

http://www.ibm.com/servers/eserver/support/xseries/allproducts/installing.html

The team that wrote this redbookThis redbook was produced by a team of specialists from around the world working at the International Technical Support Organization, Poughkeepsie Center.

Lydia Parziale is a Project Leader for the ITSO team in Poughkeepsie, New York with domestic and international experience in technology management including software development, project leadership, and strategic planning. Her areas of expertise include e-business development and database management technologies. Lydia is a Certified IT Specialist with an MBA in Technology

Management and has been employed by IBM for 23 years in various technology areas.

David T. Britt is a Software Engineer for IBM in Research Triangle Park, NC, working specifically with the z/OS Communications Server product. He is a subject matter expert in the Simple Networking Management Protocol (SNMP) and File Transfer Protocol (FTP), and has written educational material for both in the form of IBM Technotes, Techdocs, and Webcasts. He holds a degree in Mathematical Sciences from the University of North Carolina in Chapel Hill, and is currently pursuing a master of science in Information Technology and Management

from the University of North Carolina in Greensboro.

xx TCP/IP Tutorial and Technical Overview

http://www.ibm.com/systems/p/library/index.htmlhttp://www.ibm.com/servers/eserver/iseries/tcpip/index.htmlhttp://www.ibm.com/servers/eserver/support/xseries/allproducts/installing.html

Chuck Davis is a Security Architect in the U.S. He has 12 years of experience in IT security field. He has worked at IBM for nine years. His areas of expertise include IT security and privacy. He has written extensively about UNIX/Linux and Internet security.

Jason Forrester is an IT Architect for IBM Global Technology Services in Boulder, CO. He has more than 12 years of experience with network communications. Specializing in IT strategy and architecture, Jason has designed large-scale enterprise infrastructures. He holds a CCIE certification and his work has lead to multiple patents on advanced networking concepts.

Dr. Wei Liu received his Ph.D. from Georgia Institute of Technology. He has taught TCP/IP networks in the University of Maryland (UMBC campus) and he has participated in ICCCN conference organization committees. Dr. Liu has given lectures at Sun Yat-Sen University and Shantou University in Next Generation Networks (NGNs). With more than 30 technical publications (in packet networks, telecommunications, and standards), he has received several awards from ATIS

committees. Dr. Wei Liu has more than 10 years of telecom industry experience, having participated in various network transformation projects and service integration programs. Currently, he is investigating new infrastructure opportunities (virtualization, network, services, security, and metadata models) that can lead to future offering and new capabilities.

Preface xxi

Thanks to the following people for their contributions to this project and laying the foundation for this book by writing the earlier version:

Adolfo Rodriguez, John Gatrell, John Karas, Roland Peschke, Srinath Karanam, and Martn F. MaldonadoInternational Technical Support Organization, Poughkeepsie Center

Become a published authorJoin us for a two- to six-week residency program! Help write an IBM Redbook dealing with specific products or solutions, while getting hands-on experience with leading-edge technologies. You'll have the opportunity to team with IBM technical professionals, Business Partners, and Clients.

Your efforts will help increase product acceptance and client satisfaction. As a bonus, you'll develop a network of contacts in IBM development labs, and increase your productivity and marketability.

Find out more about the residency program, browse the residency index, and apply online at:

ibm.com/redbooks/residencies.html

Carolyn Matthews is an IT Architect for IBM Global Technology Services in South Africa. She is an infrastructure architect for one of South Africas largest accounts. She also acts as a consultant, using various IBM techniques. Carolyn holds an honors degree in Information Systems and is currently pursuing her masters degree in Information Systems. Her areas of expertise include TCP/IP networks, IT architecture, and new technologies.

Nicolas Rosselot is a Developer from Santiago, Chile. He has most recently been teaching an Advanced TCP/IP Networking class at Andres Bello University.

xxii TCP/IP Tutorial and Technical Overview

http://www.redbooks.ibm.com/residencies.htmlhttp://www.redbooks.ibm.com/residencies.html

Comments welcomeYour comments are important to us!

We want our Redbooks to be as helpful as possible. Send us your comments about this or other Redbooks in one of the following ways:

Use the online Contact us review redbook form found at:

ibm.com/redbooks

Send your comments in an e-mail to:

[email protected]

Mail your comments to:

IBM Corporation, International Technical Support OrganizationDept. HYTD Mail Station P0992455 South RoadPoughkeepsie, NY 12601-5400

Preface xxiii

http://www.redbooks.ibm.com/http://www.redbooks.ibm.com/http://www.redbooks.ibm.com/contacts.html

xxiv TCP/IP Tutorial and Technical Overview

Part 1 Core TCP/IP protocols

The Transmission Control Protocol/Internet Protocol (TCP/IP) suite has become the industry-standard method of interconnecting hosts, networks, and the Internet. As such, it is seen as the engine behind the Internet and networks worldwide.

Although TCP/IP supports a host of applications, both standard and nonstandard, these applications could not exist without the foundation of a set of core protocols. Additionally, in order to understand the capability of TCP/IP applications, an understanding of these core protocols must be realized.

With this in mind, Part I begins with providing a background of TCP/IP, the current architecture, standards, and most recent trends. Next, the section explores the two aspects vital to the IP stack itself. This portion begins with a discussion of the network interfaces most commonly used to allow the protocol suite to interface with the physical network media. This is followed by the protocols that must be implemented in any stack, including protocols belonging to the IP and transport layers.

Part 1

Copyright IBM Corp. 1989-2006. All rights reserved. 1

Finally, other standard protocols exist that might not necessarily be required in every implementation of the TCP/IP protocol suite. However, there are those that can be very useful given certain operational needs of the implementation. Such protocols include IP version 6, quality of service protocols, and wireless IP.

2 TCP/IP Tutorial and Technical Overview

Chapter 1. Architecture, history, standards, and trends

Today, the Internet and World Wide Web (WWW) are familiar terms to millions of people all over the world. Many people depend on applications enabled by the Internet, such as electronic mail and Web access. In addition, the increase in popularity of business applications places additional emphasis on the Internet. The Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite is the engine for the Internet and networks worldwide. Its simplicity and power has led to its becoming the single network protocol of choice in the world today. In this chapter, we give an overview of the TCP/IP protocol suite. We discuss how the Internet was formed, how it developed, and how it is likely to develop in the future.

1

Copyright IBM Corp. 1989-2006. All rights reserved. 3

1.1 TCP/IP architectural model

The TCP/IP protocol suite is so named for two of its most important protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP). A less used name for it is the Internet Protocol Suite, which is the phrase used in official Internet standards documents. In this book, we use the more common, shorter term, TCP/IP, to refer to the entire protocol suite.

1.1.1 Internetworking

The main design goal of TCP/IP was to build an interconnection of networks, referred to as an internetwork, or internet, that provided universal communication services over heterogeneous physical networks. The clear benefit of such an internetwork is the enabling of communication between hosts on different networks, perhaps separated by a large geographical area.

The words internetwork and internet are simply a contraction of the phrase interconnected network. However, when written with a capital I, the Internet refers to the worldwide set of interconnected networks. Therefore, the Internet is an internet, but the reverse does not apply. The Internet is sometimes called the connected Internet.

The Internet consists of the following groups of networks:

Backbones: Large networks that exist primarily to interconnect other networks. Also known as network access points (NAPs) or Internet Exchange Points (IXPs). Currently, the backbones consist of commercial entities.

Regional networks connecting, for example, universities and colleges.

Commercial networks providing access to the backbones to subscribers, and networks owned by commercial organizations for internal use that also have connections to the Internet.

Local networks, such as campus-wide university networks.

In most cases, networks are limited in size by the number of users that can belong to the network, by the maximum geographical distance that the network can span, or by the applicability of the network to certain environments. For example, an Ethernet network is inherently limited in terms of geographical size. Therefore, the ability to interconnect a large number of networks in some hierarchical and organized fashion enables the communication of any two hosts belonging to this internetwork.


Figure 1-1 shows two examples of internets. Each consists of two or more physical networks.

Figure 1-1 Internet examples: Two interconnected sets of networks, each seen as one logical network

Another important aspect of TCP/IP internetworking is the creation of a standardized abstraction of the communication mechanisms provided by each type of network. Each physical network has its own technology-dependent communication interface, in the form of a programming interface that provides basic communication functions (primitives). TCP/IP provides communication services that run between the programming interface of a physical network and user applications. It enables a common interface for these applications, independent of the underlying physical network. The architecture of the physical network is therefore hidden from the user and from the developer of the application. The application need only code to the standardized communication abstraction to be able to function under any type of physical network and operating platform.

As is evident in Figure 1-1, to be able to interconnect two networks, we need a computer that is attached to both networks and can forward data packets from one network to the other; such a machine is called a router. The term IP router is also used because the routing function is part of the Internet Protocol portion of the TCP/IP protocol suite (see 1.1.2, The TCP/IP protocol layers on page 6).

Two networks interconnected by a router equals Internet A

Router

R

OneVirtual

NetworkNetwork 1 Network 2

Router

R Network 3Network 1 Network 2

Router

R

Multiple networks interconnected by routers(also seen as 1 virtual network, an Internet)

Two networks interconnected by a router equals Internet A

Router

R

OneVirtual

NetworkNetwork 1 Network 2

Router

R Network 3Network 1 Network 2

Router

R

Multiple networks interconnected by routers(also seen as 1 virtual network, an Internet)

Chapter 1. Architecture, history, standards, and trends 5

To be able to identify a host within the internetwork, each host is assigned an address, called the IP address. When a host has multiple network adapters (interfaces), such as with a router, each interface has a unique IP address. The IP address consists of two parts:

IP address =

The network number part of the IP address identifies the network within the internet and is assigned by a central authority and is unique throughout the internet. The authority for assigning the host number part of the IP address resides with the organization that controls the network identified by the network number. We describe the addressing scheme in detail in 3.1.1, IP addressing on page 68.

1.1.2 The TCP/IP protocol layers

Like most networking software, TCP/IP is modeled in layers. This layered representation leads to the term protocol stack, which refers to the stack of layers in the protocol suite. It can be used for positioning (but not for functionally comparing) the TCP/IP protocol suite against others, such as Systems Network Architecture (SNA) and the Open System Interconnection (OSI) model. Functional comparisons cannot easily be extracted from this, because there are basic differences in the layered models used by the different protocol suites.

By dividing the communication software into layers, the protocol stack allows for division of labor, ease of implementation and code testing, and the ability to develop alternative layer implementations. Layers communicate with those above and below via concise interfaces. In this regard, a layer provides a service for the layer directly above it and makes use of services provided by the layer directly below it. For example, the IP layer provides the ability to transfer data from one host to another without any guarantee to reliable delivery or duplicate suppression. Transport protocols such as TCP make use of this service to provide applications with reliable, in-order, data stream delivery.


Figure 1-2 shows how the TCP/IP protocols are modeled in four layers.

Figure 1-2 The TCP/IP protocol stack: Each layer represents a package of functions

These layers include:

Application layer The application layer is provided by the program that uses TCP/IP for communication. An application is a user process cooperating with another process usually on a different host (there is also a benefit to application communication within a single host). Examples of applications include Telnet and the File Transfer Protocol (FTP). The interface between the application and transport layers is defined by port numbers and sockets, which we describe in more detail in 4.1, Ports and sockets on page 144.

Transport layer The transport layer provides the end-to-end data transfer by delivering data from an application to its remote peer. Multiple applications can be supported simultaneously. The most-used transport layer protocol is the Transmission Control Protocol (TCP), which provides connection-oriented reliable data delivery, duplicate data suppression, congestion control, and flow control. We discuss this in more detail in 4.3, Transmission Control Protocol (TCP) on page 149.

Another transport layer protocol is the User Datagram Protocol (see 4.2, User Datagram Protocol (UDP) on page 146). It provides connectionless, unreliable,

Applications

Transport

Internetwork

Network Interfaceand

Hardware

Applications

TCP/UDP

ICMPIP

ARP/RARP

Network Interfaceand Hardware

.......

.......

.......

.......


best-effort service. As a result, applications using UDP as the transport protocol have to provide their own end-to-end integrity, flow control, and congestion control, if desired. Usually, UDP is used by applications that need a fast transport mechanism and can tolerate the loss of some data.

Internetwork layer The internetwork layer, also called the internet layer or the network layer, provides the virtual network image of an internet (this layer shields the higher levels from the physical network architecture below it). Internet Protocol (IP) is the most important protocol in this layer. It is a connectionless protocol that does not assume reliability from lower layers. IP does not provide reliability, flow control, or error recovery. These functions must be provided at a higher level.

IP provides a routing function that attempts to deliver transmitted messages to their destination. We discuss IP in detail in Chapter 3, Internetworking protocols on page 67. A message unit in an IP network is called an IP datagram. This is the basic unit of information transmitted across TCP/IP networks. Other internetwork-layer protocols are IP, ICMP, IGMP, ARP, and RARP.

Network interface layer The network interface layer, also called the link layer or the data-link layer, is the interface to the actual network hardware. This interface may or may not provide reliable delivery, and may be packet or stream oriented. In fact, TCP/IP does not specify any protocol here, but can use almost any network interface available, which illustrates the flexibility of the IP layer. Examples are IEEE 802.2, X.25 (which is reliable in itself), ATM, FDDI, and even SNA. We discuss some physical networks and interfaces in Chapter 2, Network interfaces on page 29.

TCP/IP specifications do not describe or standardize any network-layer protocols per se; they only standardize ways of accessing those protocols from the internetwork layer.


A more detailed layering model is included in Figure 1-3.

Figure 1-3 Detailed architectural model

1.1.3 TCP/IP applications

The highest-level protocols within the TCP/IP protocol stack are application protocols. They communicate with applications on other internet hosts and are the user-visible interface to the TCP/IP protocol suite.

All application protocols have some characteristics in common:

They can be user-written applications or applications standardized and shipped with the TCP/IP product. Indeed, the TCP/IP protocol suite includes application protocols such as:

Telnet for interactive terminal access to remote internet hosts

File Transfer Protocol (FTP) for high-speed disk-to-disk file transfers

Simple Mail Transfer Protocol (SMTP) as an internet mailing system

These are some of the most widely implemented application protocols, but many others exist. Each particular TCP/IP implementation will include a lesser or greater set of application protocols.

They use either UDP or TCP as a transport mechanism. Remember that UDP is unreliable and offers no flow-control, so in this case, the application has to provide its own error recovery, flow control, and congestion control functionality. It is often easier to build applications on top of TCP because it is a reliable stream, connection-oriented, congestion-friendly, flow control-enabled protocol. As a result, most application protocols will use TCP, but there are applications built on UDP to achieve better performance through increased protocol efficiencies.

Most applications use the client/server model of interaction.

Applications

Transport

Internetwork

Network Interfaceand Hardware

SMTP, Telnet, FTP, Gopher...

TCP UDP

IPICMP

ARP RARP

Ethernet, Token-Ring, FDDI, X.25, Wireless, Async, ATM, SNA...


The client/server modelTCP is a peer-to-peer, connection-oriented protocol. There are no master/subordinate relationships. The applications, however, typically use a client/server model for communications, as demonstrated in Figure 1-4.

A server is an application that offers a service to internet users. A client is a requester of a service. An application consists of both a server and a client part, which can run on the same or on different systems. Users usually invoke the client part of the application, which builds a request for a particular service and sends it to the server part of the application using TCP/IP as a transport vehicle.

The server is a program that receives a request, performs the required service, and sends back the results in a reply. A server can usually deal with multiple requests and multiple requesting clients at the same time.

Figure 1-4 The client/server model of applications

Most servers wait for requests at a well-known port so that their clients know to which port (and in turn, which application) they must direct their requests. The client typically uses an arbitrary port called an ephemeral port for its communication. Clients that want to communicate with a server that does not use a well-known port must have another mechanism for learning to which port they must address their requests. This mechanism might employ a registration service such as portmap, which does use a well-known port.

For detailed information about TCP/IP application protocols, refer to Part 2, TCP/IP application protocols on p

Documents

TCP/IP Tutorial and Technical Overview - … · 5.9 Border Gateway Protocol (BGP) ... 6.5.1 Protocol overview ... 6.8.2 Border Gateway Multicast Protocol