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Packed with the latest information on TCP/IP standards and protocols
TCP/IP is a hot topic, because it's the glue that holds the Internet and the Web together, and network administrators need to stay on top of the latest developments. TCP/IP For Dummies, 6th Edition, is both an introduction to the basics for beginners as well as the perfect go-to resource for TCP/IP veterans.
The book includes the latest on Web protocols and new hardware, plus ...
Packed with the latest information on TCP/IP standards and protocols
TCP/IP is a hot topic, because it's the glue that holds the Internet and the Web together, and network administrators need to stay on top of the latest developments. TCP/IP For Dummies, 6th Edition, is both an introduction to the basics for beginners as well as the perfect go-to resource for TCP/IP veterans.
The book includes the latest on Web protocols and new hardware, plus very timely information on how TCP/IP secures connectivity for blogging, vlogging, photoblogging, and social networking. Step-by-step instructions show you how to install and set up TCP/IP on clients and servers; build security with encryption, authentication, digital certificates, and signatures; handle new voice and mobile technologies, and much more.
Find practical security tips, a Quick Start Security Guide, and still more in this practical guide.
Find out the latest on TCP/IP, the Internet and Client Server with TCP/IP For Dummies, 2nd Ed.. This book has been completely updated to reflect changes with TCP/IP. It introduces users to the basics of TCP/IP and the Internet describing important "670496rds" users must know to use TCP/IP successfully. It describes new protocols, like HTTP, along with new interactive applications, enhanced security, collaborative workgroup applications, and more.
About This Book 1
Conventions Used in This Book 2
Foolish Assumptions 2
How This Book Is Organized 3
Part I: TCP/IP from Names to Addresses 3
Part II: Getting Connected 3
Part III: Configuring Clients and Servers: Web, E-Mail, and Chat 4
Part IV: Even More TCP/IP Applications and Services 4
Part V: Network Troubleshooting and Security 4
Part VI: The Part of Tens 5
Icons Used in This Book 5
Where to Go from Here 6
Part I: TCP/IP from Names to Addresses 7
Chapter 1: Understanding TCP/IP Basics 9
Following Rules for the Internet: TCP/IP Protocols 10
Who’s in charge of the Internet and TCP/IP? 10
Checking out RFCs: The written rules 12
Examining Other Standards Organizations That Add to the Rules 13
Distinguishing Between the Internet, an Internet, and an Intranet 13
Extending Intranets to Extranets 14
Introducing Virtual Private Networks 15
Exploring Geographically Based Networks 16
Networks connected by wires and cables 16
Wireless networks 17
The geography of TCP/IP 17
Chapter 2: Layering TCP/IP Protocols 19
Taking a Timeout for Hardware 19
Starting with network connection media 20
Colliding with Ethernet 20
Stacking the TCP/IP Layers 22
Layer 1: The physical layer 23
Layer 2: The data link layer 24
Layer 3: The internet layer 24
Layer 4: The transport layer 24
Layer 5: The application layer 25
TCP/IP For Dummies, 6th Edition viii
Chewing through Network Layers: A Packet’s Journey 25
Understanding TCP/IP: More than just protocols 27
Determining whether your network has a protocol, an application, or a service 27
Plowing through the Protocol List (In Case You Thought Only Two Existed) 28
Physical layer protocols 29
Data link layer protocols 29
Internet layer protocols 29
Transport layer protocols 31
Application layer protocols 36
Chapter 3: Serving Up Clients and Servers 43
Understanding the Server Side 43
Examining the server’s job 44
Identifying types of servers 44
Using dedicated servers 45
Understanding the Client Side 45
Defining a client 45
Clients, clients everywhere 46
Answering the Question “Are You Being Served?” 46
Supporting TCP/IP with Client/Server and Vice Versa 47
Recognizing Other Internetworking Styles: Peer-to-Peer Computing 47
Determining whether peer-to-peer workgroups are still handy 48
P2P applications — P2P across the Internet 48
Chapter 4: Nice Names and Appetizing Addresses 51
What Did You Say Your Host’s Name Is? 52
Playing the numbers game 52
Identifying a computer as uniquely yours 53
Translating names into numbers 54
Taking a Closer Look at IP Addresses 54
Savoring Classful Addressing 55
Recognizing the Parts of an IP Address 56
Class A is for a few enormous networks 57
Class B is for lots of big networks 57
Class C is for millions of small networks 57
Class D is for multicasting 57
Biting Down on Bits and Bytes 58
Obtaining an IP Address 60
Choosing whether to go public or stay private 60
Obeying the network police 61
Obtaining a globally unique IP address 61
Acquiring a static address 62
Getting dynamic addresses with DHCP 62
Finding out your IP address 62
Table of Contents ix
Resolving Names and Addresses with DNS 64
Understanding the minimum amount of information about DNS 64
Using DNS to “Do Nifty Searches” 65
Describing Fully Qualified Domain Names (FQDNs) 65
Branching out into domains 66
Stalking new domains 68
Determining Whether the Internet Will Ever Fill Up 68
Choking on bandwidth 68
Panicking about not having enough addresses 69
Dishing Up More Kinds of Addresses 69
MAC: Media Access Control 69
Port numbers 70
Chapter 5: Need More Addresses? Try Subnetting and NAT 73
Working with Subnets and Subnet Masks 74
Defining subnet masks 76
Why a network has a mask when it has no subnets 76
Subnetting 101 77
Letting the DHCP Protocol Do the Work for You 79
One administrator’s nightmare is another’s fantasy 80
Understanding how the DHCP protocol works —it’s client/server again 81
Being evicted after your lease expires 82
Sharing Addresses with Network Address Translation (NAT) 83
Understanding how NAT works 83
Securing NAT 84
Using NAT and DHCP to work together 84
Swallowing NAT incompatibilities 86
Digesting NAT-PT (Network Address Translation-Protocol Translation) 87
Part II: Getting Connected 89
Chapter 6: Configuring a TCP/IP Network — the Software Side 91
Installing TCP/IP? Probably Not 91
Detecting whether TCP/IP is installed 92
Determining whether it’s IPv4, IPv6, or both 92
Savoring TCP/IP right out of the box 93
Six Steps to a Complete TCP/IP Configuration 94
Step 1: Determining whether your computer is a client or server or both 95
Step 2: Gathering client information 95
Step 3: Setting up your NIC(s) 95
TCP/IP For Dummies, 6th Edition x
Step 4: Deciding on a static IP address or a DHCP leased address 96
Step 5: Choosing how your host will translate names into IP addresses 97
Step 6: Gathering server information 97
Setting TCP/IP Client Properties 97
Configuring TCP/IP on a Mac OS X client 98
Configuring TCP/IP on a Linux or Unix client 100
Configuring a TCP/IP client on Windows Vista 102
Configuring a TCP/IP client on Windows XP 103
Setting TCP/IP Server Properties 104
Installing TCP/IP from Scratch 105
Feasting on Network Files 107
The local hosts file 107
The trusted hosts file, hostsequiv 109
Freddie’s nightmare: Your personal trust file 110
The services file 111
Daemons Aren’t Devils 113
Relishing your daemons113
Finding the daemons on your computer 113
Chapter 7: Networking SOHO with Wireless 115
Gulping the Minimum Hardware Details 116
Setting Up a Home Wireless Network in Four Steps 118
Step 1: Choose your wireless hardware 118
Step 2: Connect your wireless router 120
Step 3: Set up your wireless router 121
Step 4: Connect your computers 124
Securing Your Network 124
Securing the wired side 125
Securing the wireless side 125
Broadband for Everyone? We Hope 128
Level 1: Using wireless hotspots 128
Level 2: Paying for broadband wireless service 129
Level 3: Going anywhere you want to connect to the Internet with WiMAX 129
Chapter 8: Advancing into Routing Protocols 131
Understanding Routing Lingo 132
Routing Through the Layers — the Journey of a Packet 135
A new message heads out across the Net 135
The message visits the router 137
Into an Internet router and out again 139
Reaching the destination 140
Table of Contents xi
Getting a Handle on How Routers Work 143
Getting Started with Routers 146
Swallowing Routing Protocols 148
Nibbling on IGP protocols 149
Exterior Gateway Protocols (EGP) 152
Understanding How BGP Routers Work 154
Juicing Up Routing with CIDR 154
C Is for Classless 156
CIDR pressing the routing tables 157
You say “subnet,” aggregating.net says “aggregate” 159
Securing Your Router 159
Coring the apple with Denial of Service (DoS) Attacks 160
Hijacking routers 160
Eavesdropping on BGP 161
It’s so sad 161
S-BGP (Secure BGP): Proposals to make BGP routing secure 161
Chapter 9: IPv6: IP on Steroids 163
Say Hello to IPv6 163
Digesting IPv4 limitations 164
Absorbing IPv6 advantages 164
If It Ain’t Broke, Don’t Fix It — Unless It Can Be Improved 165
Wow! Eight Sections in an IPv6 Address? 165
Why use hexadecimal? 166
There’s good news and there’s bad news 166
Take advantage of IPv6 address shortcuts 167
Special IPv6 Addresses 169
IPv6 — and the Using Is Easy 169
Checking out the network with autodiscovery 170
Ensuring that your address is unique 171
Automatically assigning addresses 172
Realizing that autoregistration says “Let us serve you” 172
IPv6 Installation 173
Configuring IPv6 on Windows XP and Windows Server 2003 173
Welcoming IPv6 to Mac OS X175
Getting started with IPv6 in Unix and Linux 175
Other Delicious IPv6 Morsels 176
Security for all 176
Faster, better multimedia 178
Support for real-time applications 178
Improved support for mobile computing 178
Share the Planet — IPv6 and IPv4 Can Coexist 179
Stacking IPv4 and Iv6 179
Tunneling IPv6 through IPv4 180
Whew — You Made It! 180
TCP/IP For Dummies, 6th Edition xii
Chapter 10: Serving Up DNS (The Domain Name System) 181
Taking a Look at the DNS Components 182
Going Back to DNS Basics 183
Revisiting Client/Server with DNS 184
Dishing up DNS client/server definitions 184
Snacking on resolvers and name servers 184
Who’s in charge here? 186
Serving a DNS client’s needs 186
Oops! Can’t help you 187
Who’s Responsible for Name and Address Information? 187
Understanding Servers and Authority 189
Primary name server: Master of your domain 189
Secondary name servers 190
Caching servers 192
Understanding Domains and Zones 193
Problem Solving with Dynamic DNS (DYNDNS) 195
Diving into DNSSEC (DNS Security Extensions) 195
Why does DNS need DNSSEC? 196
Glimpsing behind the scenes of DNSSEC 197
Part III: Configuring Clients and Servers: Web, E-Mail, and Chat 199
Chapter 11: Digesting Web Clients and Servers 201
Standardizing Web Services 201
Deciphering the Languages of the Web 202
HTML 4 204
HTML + MIME = MHTML 205
Java and other Web dialects 205
Hypertext and hypermedia 206
Understanding How Web Browsing Works 207
Serving up a Web page 207
Storing user information as cookies 209
Managing cookies with your browser 210
Dishing up multimedia over the Internet 212
Feeding Web Pages with Atom and RSS 214
Reducing the Web’s Wide Waistline to Increase Speed 215
Proxy Serving for Speed and Security 218
Caching pages 219
Improving security with filtering 220
Setting up a proxy client 220
Finishing touches 223
Table of Contents xiii
Setting Up a Caching Proxy Server 223
Outlining the general steps for installing and configuring squid 223
Configuring squid for Microsoft Windows Server 2008 224
Browsing Securely 228
Ensuring that a site is secure 228
Using your browser’s security features 229
Setting Up a Web Server 230
Setting up the Apache HTTP Server 231
Speeding up Apache 234
Making Apache more secure 234
Adding Security to HTTP 235
Taking a look at HTTPS 236
Getting up to speed on SSL 236
Stepping through an SSL Transaction 237
Using Digital Certificates for Secure Web Browsing 238
Chapter 12: Minimum Security Facilities 239
What’s the Worst That Could Happen? 239
Jump-Starting Security with the Big Three 240
Installing a personal firewall 241
Vaccinating your system with the anti-s 242
Encrypting data so snoopers can’t read it 243
Adding a Few More Basic Protections 243
Chapter 13: Eating Up E-Mail 245
Getting the Big Picture about How E-Mail Works 245
Feasting on E-Mail’s Client-Server Delights 246
E-mail clients 246
E-mail clients versus Web mail clients 247
E-mail servers 247
Postfix: Configuring the fastest-growing MTA 249
Sharpening the Finer Points of Mail Servers 252
Transferring e-mail by way of store-and-forward 253
Transferring e-mail by way of DNS MX records 254
Understanding How SMTP Works with MTAs 255
Defining E-Mail Protocols 255
Adding More Protocols to the Mix 256
DNS and its MX records 258
TCP/IP For Dummies, 6th Edition xiv
Chapter 14: Securing E-Mail 261
Common Sense: The Most Important Tool in Your Security Arsenal 261
Being Aware of Possible Attacks 262
Popping up and under 263
Getting spied on 263
Meeting malware 265
Have you got anything without spam? Spam, spam, spam! 266
Finding Out Whether You’re a Victim 267
Playing Hide-and-Seek with Your E-Mail Address 268
Layering Security 269
Layer 1: Letting your ISP protect your network 269
Layer 2: Building your own walls 270
Layer 3: Securing e-mail on the server side 271
Layer 4: Securing e-mail on the client side 274
Layer 5: Suitely extending e-mail security 278
Using Secure Mail Clients and Servers 278
Setting up a secure IMAP or POP client 279
Setting up a secure mail server 281
Encrypting e-mail 281
Chapter 15: Beyond E-Mail: Social Networking and Online Communities 285
Thumbing to Talk About 286
Choosing a Communication Method 287
Getting together with IRC 288
Jabbering with XMPP 288
Feeding Your Craving for News 289
Getting Even More Social 290
Part IV: Even More TCP/IP
Applications and Services 291
Chapter 16: Mobile IP — The Moveable Feast 293
Going Mobile 294
Understanding How Mobile IP Works 294
Sailing into the Future: Potential Mobile IPv6 Enhancements 296
Mobilizing Security 297
Understanding the risks 297
Using basic techniques to protect your mobile devices 298
Table of Contents xv
Chapter 17: Saving Money with VoIP (Voice Over Internet Protocol) 299
Getting the Scoop on VoIP 299
Getting Started Using VoIP 300
Step 1: Get broadband 300
Step 2: Decide how to call 301
Step 3: Make the call 302
Step 4: Convert the bits back into voice (with VoIP software) 303
Step 5: Converse 303
Yo-Yo Dieting: Understanding How VoIP Packets Move through the Layers 304
Trekking the Protocols from RTP to H323 304
Talking the talk with the TCP/IP stack and more 305
Ingesting VoIP standards from the ITU 306
Vomiting and Other Vicious VoIP Vices 306
Securing Your Calls from VoIP Violation 306
You, too, can be a secret agent 307
Authenticating VoIP-ers 307
Keeping voice attacks separate from data 308
Defending with firewalls 308
Testing Your VoIP Security 308
Chapter 18: File and Print Sharing Services 309
Defining Basic File Sharing Terms 309
Using FTP to Copy Files 310
Understanding how FTP works 310
Using anonymous FTP to get good stuff 311
Choosing your FTP client 312
Transferring the files 312
Securing FTP file transfers 315
Using rcp or scp to Copy Files 316
Sharing Network File Systems 317
Nifty file sharing with NFS (Network File System) 317
Solving the buried file update problem with NFSv4 318
Examining the mount Protocol 319
Configuring an NFS Server 320
Step 1: Edit the exports file 321
Step 2: Update the netgroup file 321
Step 3: Start the daemons 322
Configuring an NFS Client 323
TCP/IP For Dummies, 6th Edition xvi
Picking Up Some NFS Performance Tips 324
Hardware tips 324
Server tips 325
Client tips 325
Weighing performance against security 325
Getting NFS Security Tips 325
Sharing Files Off the Stack 326
Using Windows network shares 326
Using Samba to share file and print services 327
Working with Network Print Services 328
Valuing IPP features 329
Setting up Windows Server 2008 print servers over IPP 330
Printing with the Common Unix Print System (CUPS) 331
Chapter 19: Sharing Compute Power 333
Sharing Network Resources 333
Accessing Remote Computers 334
Using a telnet client 334
“R” you ready for more remote access? 335
Executing commands with rsh and rexec 335
Securing Remote Access Sessions 336
Taking Control of Remote Desktops 337
Sharing Clustered Resources 338
Clustering for high availability 338
Clustering for load balancing 338
Clustering for supercomputing 339
Sharing Compute Power with Grid and Volunteer Computing 339
Part V: Network Troubleshooting and Security 341
Chapter 20: Staying with Security Protocols 343
Determining Who Is Responsible for Network Security 344
Following the Forensic Trail: Examining the Steps for Securing Your Network 344
Step 1: Prescribing Preventive Medicine for Security 345
Step 2: Observing Symptoms of Malware Infection 347
Uncovering more contagions 348
Step 3: Diagnosing Security Ailments with netstat, ps, and Logging 355
Monitoring network use with ps 355
Nosing around with netstat 357
Examining logs for symptoms of disease 362
Syslog-ing into the next generation 363
Microsoft proprietary event logging 370
Table of Contents xvii
Chapter 21: Relishing More Meaty Security 373
Defining Encryption 374
Advancing Encryption with Advanced Encryption Standard (AES) 375
Peering into Authentication 376
Do you have any ID? A digital certificate will do 377
Getting digital certificates 377
Using digital certificates378
Checking your certificates 379
Coping with certificate problems 380
IPSec (IP Security Protocol): More Authentication 381
Kerberos — Guardian or Fiend? 382
Understanding Kerberos concepts 382
Playing at Casino Kerberos 383
Training the dog — one step per head 384
Setting up a Kerberos server step by step 385
Setting up a Kerberos client step by step 387
Chapter 22: Troubleshooting Connectivity and Performance Problems 389
Chasing Network Problems from End to End 390
Getting Started with Ping 390
Pinging away with lots of options 391
And now, for “some-ping” completely different: Running ping graphically 393
Death by ping 395
Diagnosing Problems Step by Step 396
Pinging yourself and others 396
Using nslookup to query a name server 401
Using traceroute (tracert) to fi nd network problems 403
Simplifying SNMP, the Simple Network Management Protocol 406
Just barely describing how SNMP works 406
Using SMNP programming free 407
Part VI: The Part of Tens 411
Chapter 23: Ten More Uses for TCP/IP 413
Chapter 24: Ten More Resources for Information about TCP/IP Security 417
In This Chapter
As you may have seen in Chapter 1, a protocol is the set of agreed-upon practices, policies, and procedures used for communication. In this book, we're concerned with TCP/IP as the protocol for communication between two or more computers. But TCP/IP is actually a large suite of pieces that work together.
What's a suite, you ask? In a hotel, a suite is a collection of rooms that are treated as a single unit. Similarly, the TCP/IP suite is a collection of protocols, named after two of the original pieces, TCP and IP.
Now you might say, "A suite is too big. Can I just rent a room?" Nope. Sorry. The protocols in the TCP/IP suite move the data from one network layer to another and interact with one another. You can't really have a functional network with just one of the TCP/IP protocols.
In Chapter 5, we talk about layer cakes -- Figure 6-1 shows the TCP/IP five-layer cake with some of the protocols drawn on the layers. You don't need every protocol on the cake to run a network application, but you need at least a taste from each layer. So even though you may not use all the rooms in the suite, you definitely need more than one.
Getting the picture? Good, but this is as far as we're going in comparing TCP/IP to a hotel room. That's because you need to know that there's more to TCP/IP than just TCP and IP. To help you understand, we're going for an analogy that lets you compare all the pieces to something more familiar. Read on.
Many people try to compare the TCP/IP protocol to a Swiss Army knife, which has cutting blades of various sizes, a corkscrew, scissors, a nail file, and so on. The analogy works pretty well except for one thing. The really cool Swiss Army knives, with all those clever and handy pieces, are too big to have with you all the time. They'll poke a hole in your pocket!
So we have a different analogy for you. TCP/IP is like a complete set of dinnerware: plates, bowls, glasses, forks, spoons, and yes, even knives. And TCP/IP continues to expand, which means we can also include cups and saucers, wine glasses, the cream pitcher, finger bowls, and matching salt and pepper shakers. When we say complete, we mean complete! Okay, okay. We're getting carried away with the dinnerware idea, maybe. We suspect you probably eat off paper plates as often as we do. But TCP/IP doesn't know or care whether your plates are paper, stoneware, or bone china. A plate is a plate.
Many pieces of the TCP/IP suite function as protocols, applications, and services. In this and the next six chapters, as we talk about all the great things you can do with TCP/IP, we'll keep you well informed of whether you're using a TCP/IP protocol, a network service, or an application -- and highlight the places where the same name applies to one or more of these things.
To kick off the TCP/IP dinnerware analogy, imagine a large bowl. You can use that one bowl in various roles, in more than one room:
TCP/IP's modular, layered design makes it easy to innovate and add new components. If you envision a new network service, as you go about designing the server and client applications, you can simultaneously design a new protocol to add to the TCP/IP suite. The protocol enables the server application to offer the service and lets the client application consume that service. This elegant simplicity is a key advantage of TCP/IP.
RFC Alert: If you create a new protocol/application/service combination for the Internet, be sure to follow the RFC (Request For Comments) process described in Chapter 2. Follow the instructions in the Appendix, and get a copy of RFC 1543, "Instructions to RFC Authors."
In the fabric of a network, you find the protocol/application/service relationship so tightly woven together that it may be very difficult to distinguish the threads in the cloth. We use FTP as an example. FTP stands for file transfer protocol, but it's not only a protocol -- FTP is also a service and an application. (Don't worry about FTP itself at this point -- it's just an example. If you need to learn how to use FTP, check out Chapter 9.) In this section, we show you how the FTP service, application, and protocol work together to move files around the network.
FTP is three, three, three things at once -- application, service, and protocol. Suppose you need to copy a file from a remote computer. Without the application, your computer doesn't know that you want to copy. Without the service, you don't get a connection to the remote computer that has the files you need. Without the protocol, the client and server can't communicate.
Most of the time, you know from the context whether someone is referring to the service, the application, or the protocol. If you can't quite tell, maybe it doesn't really matter.
And now, on to the protocols!
Hold on tight -- here come the pieces in the TCP/IP protocol suite, listed in no particular order.
The Internet Protocol, IP, is responsible for basic network connectivity. IP is the plate in a basic place setting. When you're eating, you need a plate to hold your food. When you're networking, you need a place to put (send and receive) data -- that place is a network address.
The core of IP works with Internet addresses (you can find the details about these addresses in Chapters 13 and 14). Every computer on a TCP/IP network must have a numeric address. The IP on your computer understands how and where to send messages to these addresses.
While IP can take care of addressing, it can't do everything to make sure that your data gets to where it's going correctly and in one piece. IP doesn't know or care when a packet gets lost and doesn't arrive. So you need some other protocols to ensure that no packets and data are lost and that the packets are in the right order.
All of this is true for both IP version 4 and the new version 6 (IPv6, originally called IPng). IPv6 is just bigger and better. So if IP is a plate, IPv6 is a serving platter.
Once the food is on your plate, you need something to get it into your mouth without dropping it all over your lap. In your place setting, this is the spoon. Yeah, sure, you could use a fork, and some of you can probably even eat your peas from a knife without losing any, but a spoon is the most reliable implement for most foods. Try eating soup with a fork!
TCP, the Transmission Control Protocol, is our network spoon. No matter what kind of data you have, TCP makes sure that nothing is dropped. TCP uses IP to deliver packets to those upper-layer applications and provides a reliable stream of data among computers on the network. Error checking and sequence numbering are two of TCP's more important functions. Once a packet arrives at the correct IP address, TCP goes to work. On both the sending and receiving computers, it establishes a dialog to communicate about the data that is being transmitted. TCP is said to be "connection oriented" because it tells the network to resend lost data.
Theoretically, you can have TCP without IP. Some other network mechanism besides IP can deliver the data to an address, and TCP can still verify and sequence that data. But in practice, TCP is always used with IP.
As just mentioned, your TCP network spoon does the best job on that homemade cream of mushroom soup. In contrast, the User Datagram Protocol, UDP, is like your fork. You can do a pretty good job of cleaning your plate with a fork, and though it's not as reliable as TCP, UDP nevertheless gets a lot of data across the network.
UDP uses IP to deliver packets to upper-layer applications and provides a flow of data among computers. UDP provides neither error checking nor sequence numbering, although these features can be added by the application that has chosen to use UDP. This protocol is said to be "connectionless" because it does not provide for resending data in case of error.
NFS (Network File System), DNS (Domain Name System), and RPC (Remote Procedure Call) application programming interfaces use UDP. The protocols, applications, and services for NFS and DNS are discussed in detail in Chapters 10 and 11 respectively.
Figure 6-2 shows the relationship between IP, TCP, and UDP, and the applications at the upper layers. All the applications shown are provided with TCP/IP. If you write your own TCP/IP applications, you can draw those in on the picture, too.
You have to have connections -- or do you?
TCP/IP communicates among the layers in different ways. These methods are either connectionless or connection oriented.
Connection-oriented communication is reliable and pretty easy to understand. When two computers are communicating with each other, they "connect." Each understands what the other one is doing. The sending computer lets the receiving computer know that data is on the way. The recipient acknowledges receipt of the data (called ACKs for short) or denies receipt of the data (negatively acknowledges, or NACKs). This ACKing and NACKing is called handshaking.
Suppose you send a fax to your friend Ken in Tokyo. If you want to be sure he gets it, you might call and say, "I'm faxing you the baseball results now. Call me when you get it." Once the fax comes in and Ken checks it over to make sure it is readable, he calls you and says, "Thanks. I'm thrilled to hear that the Cubs won the World Series." That's connection-oriented communication.
But suppose you send the fax without first notifying your friend. And, for some reason, it never gets there. Ken doesn't know to expect anything, so he doesn't know that anything is lost. That's connectionless communication. When connectionless data is sent, the computers involved know nothing about each other or the data being sent. If you're on the receiving end, no one tells you that you're about to get anything. If you're sending data, no one bothers to mention whether or not they got it or if it was totally garbled.
With this in mind, you might wonder why any data communications would be done in connectionless mode. But there's a time and place for everything. First, communication is faster without the ACKs and NACKs. Second, not every network message needs to be as accurate as your e-mail. Finally, some applications do their own error checking and reliability processing, so they don't need the connection-oriented overhead of TCP.
When all you know is the TCP/IP address of the remote computer, the Address Resolution Protocol, ARP, finds that computer's network interface card hardware address. ARP is like your salad plate. With its load of addresses for the devices on the network, ARP is closely allied with IP, the dinner plate. (See Chapter 13 for more on TCP/IP addresses.)
When all you know is the network interface card (NIC) hardware address of a remote computer, the Reverse Address Resolution Protocol, RARP, finds the computer's TCP/IP address. RARP is your salad fork because it goes with your salad plate. We don't mean to suggest any relationship to the UDP dinner fork, however. Hey, there are places where we have to stretch the analogy a little, okay?
The Internet Control Message Protocol, ICMP, reports problems and relays other network-specific information, such as an error status from some network device. IP detects the error and passes it to ICMP. A very common use of ICMP is the echo request generated by the Ping command. ICMP is like your crystal water glass, the one that "pings" so nicely when you accidentally hit it with the fork you're waving around to emphasize your point in that argument about the greenhouse effect.
The File Transfer Protocol, FTP, is like your knife. Not a special steak knife or a little butter knife; just the regular dinner knife. It's FTP that helps you copy files between two computers. You use your FTP knife to either "pull" the files from the remote computer (known as downloading) or "push" them to the remote computer (known as uploading). As described earlier in this chapter, FTP is also the name of an application and a service, so we'll be looking at it again (and again).
Check out Chapter 9 for lots more on FTP.
The Trivial File Transfer Protocol, TFTP, loads files down line from a TFTP server. Another use of TFTP is in Digital Equipment Corporation's remote installation service, where you install a computer's operating system from another computer's files via the TFTP protocol. This is called a network installation.
TFTP is your butter knife, a smaller version of the FTP dinner knife. You can see why we needed to be a little specific about your FTP knife.
The Simple Mail Transfer Protocol, SMTP, is the protocol for Internet e-mail. It transfers e-mail messages among computers. The messages may go directly from the sender's computer to the recipient's, or the messages may proceed through intermediary computers in a process known as store and forward.
SMTP is like your wine goblet. Again, a disclaimer is in order: We don't mean to suggest any relationship to the ICMP water glass, which you managed to knock over anyway as that discussion heated up.
E-mail, of course, is one of the Big Four network applications (along with file transfer, signing on to remote computers, and Web browsing), and many vendors have their own mail protocols. SMTP is the mail transfer protocol for the Internet. UNIX mail understands SMTP, but other operating systems do not. When users of SMTP-ignorant computers need to get out to the outside world (in other words, get to the Internet), a special SMTP gateway must be established for that communication.
Chapter 7 tells you more about SMTP gateways and e-mail in general.
The latest version of the Post Office Protocol, POP3, provides basic client/server features that help you download your e-mail from a POP3 mail server to your computer. POP3 is like the corkscrew that helps you get the e-mail wine out of the bottle and into your wine goblet. If your computer has an SMTP connection to a neighboring computer, you don't need to use POP3.
POP3 was designed to allow home users to move their e-mail off their Internet Service Provider's (ISP's) computers and onto their own. You need a POP3 mail client to communicate with a POP3 mail server.
See Chapter 7 for more information about POP3 clients and servers.
The latest version of the Internet Message Access Protocol (Version 4, Revision 1), IMAP4, provides sophisticated client/server capabilities that give you choices about how you handle your e-mail. IMAP4 provides a richer set of features than POP3. IMAP4 is like a fancy decanter that holds the wine better than the bottle does but still helps you get the e-mail wine into your wine goblet. If your computer has an SMTP connection to a neighboring computer, you don't need to use IMAP4. You still might choose to use IMAP4, however, because of its sparkling functionality. You need an IMAP4 client to communicate with an IMAP4 mail server.
POP3 and IMAP4 don't interoperate. You can't use a POP3 client with an IMAP4 server or an IMAP4 client with a POP3 server, but you can find clients and servers that speak both protocols.
LDAP (pronounced as L-dap, which rhymes with cap) is the way to look up information such as user names and e-mail addresses in an X.500-compatible directory service. Whew! That's a mouthful. Think of the directory service as a big set of white pages containing all of the information you might need. The problem is, there isn't just one set of white pages. Each organization has several.
LDAP helps applications get what they need from any or all sets of white pages. LDAP is like the condiment tray filled with pickles, olives, capers, relishes, a little bit of this, a little bit of that, each in its own separate compartment.
X.500, part of ISO OSI, had its own Directory Access Protocol (DAP), but neither X.500 or DAP became popular. LDAP capitalizes on the work done by X.500 and DAP's visionary designers.
The time-of-day clocks that computers maintain are synchronized by the Network Time Protocol, NTP. Time-stamping is important in all sorts of applications, providing everything from document creation dates to network routing date/time information. NTP gets the time data from a time-server computer, which gets it from an official source, such as the United States National Institute of Standards and Technology. In continental Europe, ISO provides a time service used with banking transactions and stock transfers.
NTP is like your seafood fork. You know, the tiny one you use (or try to, anyway) to get the lobster meat out. NTP is a special-purpose tool, just right for the job it's made for.
The HyperText Transfer Protocol (HTTP) transfers HyperText Markup Language (HTML) and other components from the servers on the World Wide Web to your browser client. (There's lots more about the World Wide Web in Chapter 12.)
HTTP is like a large pitcher filled with sangria -- a lot of delicious ingredients that are combined to make something even better. (Candace makes the world's best sangria; but in a sick twist of fate, she's become allergic to red wine.) The HTTP pitcher brings the various Web ingredients to you. It's similar to the wonders of e-mail brought to you by the SMTP wine goblet.
When you acquire a new computer, it needs an operating system. If the computer has no disks for storage, you can download the operating system into your computer's memory from another computer on the network. When you do, your diskless computer uses the Boot Protocol, BOOTP, to load its operating system (or other stand-alone application) via the network. Booting means loading the operating system.
If you do have disk storage on your new computer, you should install your own local operating system. Some vendors (Digital Equipment Corporation, for instance) let you perform a remote installation from another computer on the network. The remote installation copies all the operating system files to your computer's disk; from that point on, you can boot the operating system locally.
Under your network place settings is a tablecloth made of gateways and routers, which have various gateway and router protocols that allow them to exchange network topology and status information. Routing is the process of moving packets between networks. Here are the some of the most popular ones:
Chapter 18 has more information on the gateways, routers, and other hardware devices that use these protocols.
The Point to Point Tunneling Protocol (PPTP) lets you create a Virtual Private Network (VPN) on the public Internet. Using PPTP, you can have a secure link to your organization's network -- as if you were inside the building and on the LAN -- even though you're actually connected to the Internet via an Internet Service Provider (ISP). Your communication traffic can even be encrypted to ensure that no miscreants can see your data. You get all of the benefits of a global private network without any of the hassles of launching your own satellites, laying your own undersea cables, or working with any of the boring pieces from Chapter 3.
PPTP is like your napkin because it augments the tablecloth provided by the router protocols. The encryption is like an optional napkin ring.
We couldn't forget about you housekeeping haters out there when putting together the TCP/IP dinnerware. We knew you'd want a recyclable paper plate. DHCP, the Dynamic Host Configuration Protocol, is that paper plate. This protocol is a client/server solution for sharing numeric IP addresses. The DHCP paper plate (a DHCP server) maintains a pool of shared addresses -- and those addresses are recyclable. When a DHCP client computer wants to use a TCP/IP application, that client must first request an IP address from the DHCP server. The server checks the shared supply; if all the addresses are in use, the server notifies the client that it must wait until another client finishes its work and releases an IP address. If an address is available, the DHCP server sends a response to the client that contains the address.
This shared-supply approach makes sense in environments in which computers don't use TCP/IP applications all the time or in which there are not enough addresses available for all the computers that want them.
SSL (the Secure Sockets Layer, version 2) provides security by allowing applications to encrypt data that goes from a client, such as a web browser, to the matching server. (Encrypting your data means converting to a secret code. Chapter 7 discusses encrypting your e-mail.) In other words, when you buy that Lamborghini over the Web, no one but the dealer can read your credit card number. SSL version 3 allows the server to authenticate that the client is who it says it is.
SSL is like the engraved invitation you must show at the front door before you are allowed to see your glorious dining table set with all this wondrous TCP/IP dinnerware. It's the way you convince the big brute of a bouncer to let you in.
When the Web-based Lamborghini dealer checks with the bank to make sure your credit card is good, you don't want any Internet snoops to steal a peek at your credit card number. SET is the protocol that protects your credit card on the dealer's end of the sale.
There are many more pieces of TCP/IP, and new ones are being developed this very minute! The ones described in this chapter are the most important, the most visible, and the most common. All of the protocols that use an IP address must be updated so that they understand the IPv6 address. Aren't you glad you're not a TCP/IP programmer? Here are some of the protocols that have undergone extensive updating:
The changes in IPv6 also affect services such as DNS. You can read about the details in Chapter 14.
Posted May 16, 2010
I found the pace and depth just what I was looking for. The textbook I borrowed was going in too deep just on the topic of IP addresses, let alone the suite of protocols, services, etc. This book touches enough on most areas to start me on my way to other references that may go into certain things more deeply.
3 out of 3 people found this review helpful.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted April 3, 2003
They removed all the references to food on this edition; it is much better and great for a non-expert to master the basics, so one can have an intelligent conversation with network engineers. I know understand DHCP, masking, CIDR, telnet, and many other issues that were only acronynms before. It is NOT for a real network engineer, but for one who needs an overview, it's excellent. Keep to the 5th edition, avoid older verions.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted January 18, 2001
The authors' use of analogies was excessive and sometimes forced, which caused the reader to have to guess at what they were talking about (the food analogy went way too far, and chapter titles like 'Do some stuff over there' required me to read into the chapter before I could even guess that they were talking about Telnet and RLogin). If you want to learn how to use TCP/IP applications such as email, this might be a good start. If you want to get into the essence of TCP/IP, I would go somewhere else.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted February 4, 2001
If you really need to learn the basics, then this book will more or less give you the nessessary lingo to undertand tcp/ip books that are more in depth and technical. The analogies, esp. the dinnerware, actually get's in the way of the learning. (if they had left the anagies to the main dinnerware, it might have worked, but it got to the point of talking about lobster forks and pitchers of wine) On a high note, which is a large part of why I bought the book, is that it comes with a CD with the entire collection of RFC's as of the date of publication. That alone is probably worth the price. It would take considerable time to download several thousand RFC's from the web. Anyway, I'm looking for a book on Cisco Routers, and I think I'll look someplace else. If it wasn't for the CD, I'd only give it a one star.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted August 5, 2010
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Posted April 8, 2013
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