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Candace Leiden is the Chief Technologist at the Cardinal Software Group, a training and consulting corporation. Forced to learn about computers because she was afraid of slide rules, Candace has worked as a software developer, a system and network administrator, and as a database administrator and architect. She currently specializes in training and consulting on design and tuning large production databases on a variety of Linux, UNIX, and Windows 2000 operating systems. Candace is also the author of The Linux Bible, published by IDG Books Worldwide and of technical courseware for worldwide companies and international organizations. Candace met Marshall Wilensky in 1981 when they both worked at the same company. She taught him everything he knows. He gave her gray hair.
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.
Conventions Used in This Book.
How This Book Is Organized.
PART I: Basics and Buzzwords.
PART II: TCP/IP from Soup to Nuts to Desserts.
PART III: TCP/IP Stew -- a Little of This, a Pinch of That.
PART IV: The Part of Tens.
Icons Used in This Book.
Where to Go from Here.
PART I: Basics and Buzzwords.
Chapter 1: Understanding TCP/IP Basics.
Dear Emily Post: What's a Protocol?
The Protocol of Open Systems.
What's a Transport?
The TCP/IP Declaration of Independence.
Dedicated to the proposition that all vendors are created equal.
Dedicated to the proposition that all operating systems are created equal.
Chapter 2: What You Need to Know about Networks.
What's a Network?
What kinds of devices can be on a network?
How does TCP/IP fit into the network?
What a Network Can Do for You.
What a Network Can Do to You (There's No Such Thing as a Free Lunch).
Protocols and Packets and Humpty Dumpty's Fall off the Wall.
All the King's horses and all the King's men.
can put your packets together again (with the help of TCP/IP).
What's a LAN?
How Ethernet works.
With this ring.
Token ring versus Ethernet.
Fast Ethernet, Faster, Fastest and Beyond.
What's a WAN?
SOHO is Not Just a London Neighborhood.
Mother Goose Network Services, Inc..
Chapter 3: Client/Server -- the Foundation of Internetworking.
What Exactly is Client/Server, Anyway?
What client/server is.
What client/server isn't.
The Server Part of Client/Server.
The Client Part ofClient/Server.
Are You Being Served?
What Does All This Have to Do with TCP/IP?
Oh Now I Get It!
Chapter 4: TCP/IP and Internets, Intranets, and Extranets.
The Internet versus an internet.
The Internet is.
Is the Internet free?
What is the Internet backbone?
What's in store for the Internet?
Nets, Nets, and More Nets.
An intranet is.
An extranet is.
A Virtual Private Network (VPN) is.
Who's in Charge of TCP/IP and the Internet, Anyway?
IPv6, the Next Generation of TCP/IP.
Chapter 5: Luscious Layers.
ISO OSI -- More Than a Palindrome?
The ImpOSIble Dream?
Taking a Modular Approach to Networking.
The ISO OSI seven-layer cake.
Layer 1: The physical layer.
Layer 2: The data link layer.
Layer 3: The network layer.
Layer 4: The transport layer.
Layer 5: The session layer.
Layer 6: The presentation layer.
Layer 7: The application layer.
Fitting TCP/IP into the Seven-Layer Cake.
PART II: TCP/IP from Soup to Nuts to Desserts.
Chapter 6: Do You Have a Complete Set of TCP/IP Dinnerware?
The TCP/IP Protocol Suite.
TCP/IP bowls you over.
Protocol, application, or service?
The Protocols (and You Thought There Were Only Two!).
IP: Internet Protocol.
TCP: Transmission Control Protocol.
UDP: User Datagram Protocol.
ARP: Address Resolution Protocol.
RARP: Reverse Address Resolution Protocol.
ICMP: Internet Control Message Protocol.
FTP: File Transfer Protocol.
TFTP: Trivial File Transfer Protocol.
SNMP: Simple Network Management Protocol.
SMTP: Simple Mail Transfer Protocol.
POP3: Post Office Protocol, v3.
IMAP4: Internet Message Access Protocol, v4.
LDAP: Lightweight Directory Access Protocol.
NTP: Network Time Protocol.
HTTP: HyperText Transfer Protocol.
S-HTTP: Secure HTTP.
BOOTP: Boot Protocol.
RIP, OSPF, BGP: Gateway (Router) Protocols.
PPTP: Point to Point Tunneling Protocol.
DHCP: Dynamic Host Configuration Protocol.
SSL: Secure Sockets Layer.
IPSec: IP Security Protocol.
RSVP: Resource Reservation Protocol.
IPP: The Internet Printing Protocol/1.0.
The Kerberos Network Authentication Service.
And many, many more.
Chapter 7: E-Mail and Beyond -- Shipping and Handling Included.
The Medium is the Message (Sometimes).
POP3, IMAP4: Your invisible friends.
Casper, the friendly MTA.
The E-Mail Course at the TCP/IP Banquet.
E-mail addresses: @ marks the spot.
How can I find someone's e-mail address?
SMTP: The Meat and Potatoes.
MIME means a lot more than Marcel Marceau.
How an SMTP gateway works.
"Alias Smith and Jones".
Is Your E-Mail Secure?
Don't let people eavesdrop on your mail.
Wall up your network to keep out shady characters.
Avoid getting bombed, spammed, or spoofed.
Free E-mail with All the Trimmings.
Free specialized e-mail services.
Not just for English speakers.
Free e-mail reminders.
Usenet News: Sharing Info over Lunch at the Network Table.
Reading the news with a free newsreader.
Using newsgroups to find out more about TCP/IP.
Use a Web browser and mouse your way through the newsgroup.
Are E-Mail and News too Slow For You?
Messaging in an instant.
Talking the talk.
Internet Relay Chat (IRC): TCP/IP's version of CB radio.
How do you choose?
ET Should Have Used Internet Phone.
How Else Can TCP/IP Help You Communicate Over the Internet?
Chapter 8: Feasting on Information.
How Do Information Services Help Me?
What Are Hypertext and Hypermedia?
The World Wide Web (WWW).
Thanks, but I'm just looking.
Mousing across the Web.
How Does Information Get on the Web?
The Web Is a High-Calorie Feast.
Sifting through the information on the Web.
Enjoying delectable multimedia.
Attend a convention or trade show on the Web.
Reducing the Web's Wait.
Who's in Charge of the Web?
A Few Blasts from the Past Are Still Useful.
Using Archie to search FTP archives.
Gophers go-fer Internet gold.
Gopher a WAIS down the internet.
Chapter 9: Share and Share Alike.
The FTP Blue Plate Special.
Using Anonymous FTP to Get Good Stuff.
Choose Your FTP Client Application.
Using FTP to Transfer Files.
Beyond the Basics (Just a Little).
Just looking at a file.
FTPing non-text files.
Smart FTP Tricks.
Using rcp (Not Just Another Copy Program).
Chapter 10: Sharing Loaves and Fishes -- NIS and NFS.
Fishing for Information with NIS.
Figuring out what kind of information you can get with NIS.
Understanding why NIS is so popular on intranets.
What's Domain idea?
Master of your domain.
The role of slave servers.
The role of the clients.
NIS in Action.
Behind the scenes at OOPS.
The OOPS problem.
The OOPS solution.
Okay, NIS Is Great -- Are There Pitfalls?
Configuration and administration.
NIS+ is a fine kettle of fish.
Using NFS to Share Fishes er, Files.
NFS means nifty file sharing.
Why is NFS so great?
Your home away from home.
What about NFS Performance?
NFS performance tips.
Weighing performance against security.
Getting in one another's way.
There's interoperability and then there's interoperability.
Automounting -- It Sounds Illegal.
Now do I get to find out what the automounter is?
How about Some NFS Security Tips?
NIS and NFS Together.
Are NIS and NFS Used on the Internet?
WebNFS -- Technology Moves into the Future.
How to use WebNFS.
Chapter 11: Fishing in a Really Big Pond.
Getting to Know DNS.
DNS = Does Nifty Searches.
Client/Server Again -- You Can't Get Away from It.
Name servers and resolvers.
DNS's pieces and parts.
The Internet's Definition of Domain.
The internationalization of the Internet.
Fully qualified domain names.
Servers, Authority, and Other Techie Stuff.
Who's in charge here?
The primary is master of the domain.
The secondary name servers.
Servers, lies, and videotapes.
DNS versus NIS.
Finding Information about Domains.
Where is whois?
Your fishing pole: nslookup.
WINS (Windows Internet Name Service): Name Resolution According to Microsoft.
Chapter 12: Over There, Over There, Do Some Stuff, Do Some Stuff, Over There.
The Crepe Place/In Paris = TCP/IP?
Sharing Other People's Computers.
Cycle stealing -- would you steal a Harley?
You can't steal a moped.
Why did the hungry user steal cycles? To get to the restaurant on the other side of the network.
Using Telnet to Borrow Processing Power.
What you need to know before starting telnet.
The great escape.
Serving telnet where you least expect it.
Telneting in the palm of your hand.
R you Ready for MoRe Remote log-ins?
Stealing Cycles with rsh.
What? They Don't Trust You? No Problem: Rexec to the Rescue!
Another Option for Windows Users: the Multiheaded Beast.
Sniffing Out Security Holes with SSH.
PART III: TCP/IP Stew -- a Little of This, a Pinch of That.
Chapter 13: Nice Names and Agonizing Addresses.
What Did You Say Your Computer's Name Was Again?
Getting to know you .
Uniquely yours .
What's the Local Hosts File?
The Many Faces of IP Addresses.
Why bother with a number if the computer has a name?
What's in an IP address?
How Do I Get an IP Address?
The Four Sections of the IPv4 Address.
Class A is for a few enormous networks.
Class B is for lots of big networks.
Class C is for the thousands of small networks.
Class D is for multicasting.
For Math Nerds Only: Biting Down on Bits and Bytes.
Administering Subnets and Subnet Masks.
Why do I have a mask if it's not Halloween?
Expanding with Supernets and Supernet Masks.
A bit makes more than a bit of difference.
Supernets -- the bottom line.
DHCP Gives Network Administrators Time to Rest.
One administrator's nightmare is another's fantasy.
Here's how it works -- it's client/server again.
Oh no! My lease expired. Am I evicted?
Is the Internet Getting Low on Addresses?
Will the Internet Ever Run Out of Addresses?
CIDR (Classless Inter-Domain Routing) Juices up the Internet.
You say subnet, NEToRAMA says supernet.
Back to the Comfort Zone.
Chapter 14: Configuring TCP/IP -- Will Someone Please Set the Network Table?
Are the Files Already on the Table?
Configuring TCP/IP on a Windows 95 or Windows 98 Client.
Configuring TCP/IP on a Windows 2000 Server.
The Local Hosts File.
Maintaining a local hosts file.
What's in the local hosts file?
Improving TCP/IP's digestion of the local hosts file.
The Trusted Hosts File.
The Trusted Hosts Print File.
Freddie's Nightmare: Your Personal Trust File.
This is scary. Why would I ever want rhosts?
Surprise! The curse of the network administrator lives.
The Networks File.
The Internet Daemon Configuration File.
The Protocols File.
The Services File.
Dealing with the Devil.
Chapter 15: IPv6 -- IP on Steroids.
If It Ain't Broke, Don't Fix It -- Well, Maybe it Could Be Improved.
Wow! Eight Sections in an IPv6 Address?
Don't these long addresses clog network traffic?
Why use hexadecimal?
There's good news and there's bad news.
Shorthand for Non-Stenographers.
The leading zero (0000) shortcut.
The double colon (::) shortcut.
The IPv4 coexistence shortcut.
What about Subnet and Supernet Masks?
Special IPv6 Addresses.
IPv6 -- and the Using Is Easy.
Checking out the network buffet with autodiscovery.
Let someone else fill your platter -- use autoconfiguration.
Autoregistration says "Let us serve you".
Other Delicious IPv6 Morsels.
Security for all.
Faster, better multimedia.
Support for real-time applications.
Improved support for mobile computing.
Sharing the Planet -- IPv6 and IPv4 Can Coexist.
Who's Using IPv6?
Whew You Made it!
Chapter 16: Is Anyone There?
Fingering Your Friends and Enemies.
Fingering a user.
Fingering the users on a host.
Using a Finger Gateway.
Knock, Knock -- Who's There?
w-ant to Know More?
rwho There, You Devil?
ruptime, Cousin of rwho.
The World According to ARP.
The nslookup Utility.
The showmount Utility.
Reach Out and Touch Something, with ping.
ps, We Love You.
Afraid to Ask for Directions? Traceroute Tells You Where You're Going.
Chapter 17: Mobile-IP, Dialup Networking, and IP Telephony.
Mobile-IP for Hassle-Free Travel.
Mobile-IP -- too good to be true?
Connecting with Dialup Protocols.
PPP (no, not "the bathroom protocol," silly!).
SLIP your way onto the network.
Using PPTP to create VPNs (Virtual Private Networks).
In UUCP, the U lies and the C misleads.
Which dialup solution is for you?
Understanding IP Telephony.
Who's in charge of IP telephony?
VoIP -- Voice information in packets.
How can I use VoIP?
Chapter 18: The Dreaded Hardware Chapter.
Catering a Network Banquet.
Are you in charge or did you just come to eat?
What's hardware got to do with it?
Keep Layers in Mind.
Packets Chew through Network Layers.
Satisfy Your Need for Speed with Other Things That People Call Modems.
Cable me up.
ISDN: Immediate Surfing Down the Net and DSL: Darn Speedy Linkage.
Beam me down, Scotty!
Serve Your Guests with Terminal Servers.
Stretching the Network Dinner Party into a Banquet.
There's Ethernet and there's Fast Ethernet.
Who really needs to go that fast?
A Switch in Time Saves Nine Intranet Hassles.
Rowter or Rooter? Doesn't Matter.
How does routing work, anyway?
Configuring a router on Windows NT Server.
Gateways: The Ultimate Interpreters.
The Party's Over -- It's Decision Time.
Chapter 19: Security -- Will the Bad Guys Please Stand Up?
In the Good-Ol' Days.
What's Involved in Network Security?
Who's responsible for network security?
What's the worst that can happen?
IPSec (IP Security Protocol).
There's good news .
and bad news.
The TCP/IP Banquet Is By Invitation Only.
Tales from the crypt.
The X-Files -- tales of authentication.
To catch a thief.
Speaking of telnet -- go beyond the basics.
Tunneling through the Internet.
Be Aware of Security Pitfalls in Your Applications.
Put limits on TFTP.
Be careful of what's anonymous.
Don't believe everything you read, Part One: E-mail.
Don't believe everything you read, Part Two: Usenet news.
We trust only Johnny Carson and Walter Cronkite.
NFS = No File Stealing!
Sweat the small stuff!
How Promiscuous Is Your Network Interface Card?
Credit Card Shopping on the World Wide Web.
How does the S-HTTP (Secure HTTP) protocol help?
How does the SSL (Secure Socket Layer) protocol help?
E-Commerce -- a Shopper's Dream?
Watch out, Big Four!
What kind of business can you do over the Internet?
What happens when you give a credit card number on the Web.
Commonly Held Myths about Network Security.
Protecting Your Network.
Can you protect the cables?
Can you detect an unauthorized host or device on your network?
Can you keep unauthorized users off your computers?
What's a Firewall?
How a firewall works.
Types of firewalls.
Network management considerations when setting up a firewall.
Approaching Secure Environments.
Kerberos -- Guardian or Fiend?
Playing at Casino Kerberos.
Training the dog -- one step per head.
Guardian of the Gates of Microsoft.
We're CERTainly Interested in Security.
PART IV: The Part of Tens.
Chapter 20: Ten Reasons to Use TCP/IP.
You Dream of Untangling the Web.
You Want Free Entertainment.
You Want to Sell Your Wares on the Web.
You Live to Shop.
You Need E-Mail.
You Want to Run Programs on Other People's Computers.
You Want Someone to Play With.
Sneakernet Is Wearing You Out.
You Have Files to Procure.
Chapter 21: Ten Frequently Asked Questions about TCP/IP and the Internet.
What Software Do I Need to Get on the Internet?
Do I Need Linux or UNIX to Run TCP/IP?
Can I Have a Web Server and Still Have Security?
Does the Web have a Card Catalog?
What's a Cookie?
Can I Catch a Virus by Looking at a Web Page?
How Do I Read Usenet News Articles?
Why Isn't IPv6 Here Yet?
Chapter 22: Ten Strange but Real TCP/IP Network Devices (No Kidding!).
Squeaks and Squeals from Australia.
The Streets of Seattle (for Anne Marie).
An Interactive Model Railroad.
Space: The Final Frontier on the Web?
Chapter 23: Watch Your Back -- Ten Practical Security Tips.
Be CERTain You Know the Dangers.
Know What Your Browser is Doing.
Keep Your Browser's Security Up-to-Date.
Maintain Your Privacy.
Cover Your Browser's Tracks in the Windows Registry.
Some Yummy Tips About SPAM.
Chapter 24: Ten Ways to Get RFCs.
Making Friends with the Editor.
Finding the RFC Index.
Understanding entries in an RFC Index.
RFC name format.
Using the Web to Get an RFC (and more).
Visiting the RFC Editor.
Going beyond the RFC Editor.
Using Anonymous FTP to Get an RFC.
Getting an RFC via e-Mail.
Chapter 25: Ten RFCs and Web Sites Worth Tasting.
The Whole RFC Catalog.
The Hitchhiker's Guide.
Nibbling on NetGuide's Net Newbie.
Trust No One?
What Are the Webopedia and Whatis?
Reveling in TechFest.
Flipping through Internetworking Technology Overview from Cisco Systems.
Looking for Something We Missed?
A View from Mars.
Appendix: About the CD.
Using the CD with Microsoft Windows.
Using the CD with Linux.
What You'll Find.
If You Have Problems (of the CD Kind).
IDG Books Worldwide End-User License Agreement.
GNU General Public License.
Book Registration Information.
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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