Network+ Guide to Networks, 5th Edition
Chapter 10
In-depth TCP/IP Networking
At a Glance
Instructor’s Manual Table of Contents

Overview

Objectives

Teaching Tips

Quick Quizzes

Class Discussion Topics

Additional Projects

Additional Resources

Key Terms
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Lecture Notes
Overview
In Chapter 4, students learned about core protocols and subprotocols in the TCP/IP protocol
suite, addressing schemes, and host and domain naming. Students also learned that TCP/IP is a
complex and highly customizable protocol suite. This chapter builds on these basic concepts,
examining how TCP/IP-based networks are designed and analyzed. It also describes the
services and applications that TCP/IP-based networks commonly support.
Chapter Objectives
After reading this chapter and completing the exercises, the student will be able to:
 Understand methods of network design unique to TCP/IP networks, including
subnetting, CIDR, and address translation
 Explain the differences between public and private TCP/IP networks
 Describe protocols used between mail clients and mail servers, including SMTP, POP3,
and IMAP4
 Employ multiple TCP/IP utilities for network discovery and troubleshooting
Teaching Tips
Designing TCP/IP-Based Networks
1. Describe how most modern networks rely on the TCP/IP protocol suite.
2. Review TCP/IP fundamentals.
3. Note the two versions of IP.
a. Explain why this discussion on IP addressing focuses on IPv4.
4. Review the IPv4 address expressions:
a. Binary and dotted decimal
5. Remind students that many networks assign IP addresses and host names dynamically,
using DHCP, rather than statically.
6. Review network classes.
a. Emphasize that a node’s network class provides information about the segment
or network to which the node belongs.
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Subnetting
1. Define the term subnetting.
2. Discuss how networks are commonly subnetted.
a. Geographic locations
b. Departmental boundaries
c. Technology types
3. Discuss three reasons why a network administrator might separate traffic.
4. Review IPv4 addressing conventions on a network that does not use subnetting.
5. Introduce and explain classful addressing in IPv4.
6. Remind students that all IPv4 addresses consist of network and host information.
7. Explain where the network information portion of an IPv4 address (the network ID) is
located in classful addressing:
a. First 8 bits in a Class A address
b. First 16 bits in a Class B address
c. First 24 bits in a Class C address
8. Explain where the host information portion of an IPv4 address is located in classful
addressing:
a. Last 24 bits for a Class A address
b. Last 16 bits in a Class B address
c. Last 8 bits in a Class C address
9. Use Figure 10-1 to illustrate examples of IPv4 addresses separated into network and
host information according to the classful addressing convention.
10. Introduce and describe IPv4 subnet masks.
11. Use Table 10-1 to illustrate how each network class is associated with a default subnet
mask.
a. Remind students that an octet composed of all 1s in binary notation equals 255
in decimal notation and an octet composed of all 0s in binary notation equals 0
in decimal notation.
12. Define and explain the concept of ANDing.
a. Explain how to calculate a host’s network ID given its IPv4 address and subnet
mask.
b. Use Table 10-2 to illustrate ANDing.
c. Use Figure 10-2 to illustrate and example of calculating a host’s network ID.
Network+ Guide to Networks, 5th Edition
Teaching
Tip
10-4
Point out that several online sites and operating systems provide calculators that
calculate AND operations. Provide a class demonstration of the Windows
operating system calculator by navigating to the Accessories area containing the
calculator. Change the calculator view to scientific if necessary. Select “bin” for
input and practice ANDing two binary numbers of various numeric contents and
lengths.
13. Define and explain the concept of reserved addresses.
a. Describe why the network ID is considered a reserved address.
b. Describe why the broadcast address is considered a reserved address.
c. Explain why only the numbers 1 through 254 can be used for host information in
an IPv4 address.
14. Introduce and explain IPv4 subnetting techniques.
a. Note that subnetting breaks the rules of classful IPv4 addressing.
b. Describe how some of an IP address’s bits that in classful addressing would
represent host information are changed to represent network information instead.
c. Emphasize the consequence of subnetting in terms of the number of useable host
addresses available per subnet.
d. Use Table 10-3 to illustrate the numbers of subnets and hosts that can be created
by subnetting a Class B network.
e. Use Table 10-4 to illustrate the numbers of subnets and hosts that can be created
by subnetting a Class C network.
15. Introduce the topic of calculating IPv4 subnets.
a. Present and explain the formula for determining how to modify a default subnet
mask.
b. Walk though an example utilizing a leased Class C network with network ID of
199.34.89.0 and the need to divide it into six subnets.
c. Use Table 10-5 to illustrate a listing of the network ID, broadcast address, and
usable host addresses for each of the six subnets in the example Class C
network.
d. Point out that the extended network prefix for each subnet is based on which of
the additional (borrowed) network information bits are set to equal 1.
e. Point out that Class A, Class B, and Class C networks can all be subnetted;
however, each class reserves a different number of bits for network information
and each class has a different number of host information bits that can be used
for subnet information.
f. Explain how subnetting on a LAN affects LAN devices.
g. Use Figure 10-3 to illustrate and explain a situation in which a LAN running
IPv4 has been granted the Class C range of addresses that begin with 199.34.89.
Network+ Guide to Networks, 5th Edition
Teaching
Tip
10-5
Point out that several Web sites provide excellent tools to assist network
administrators in calculating subnet information. Provide a classroom
demonstration by navigating to http://www.subnetmask.info to illustrate one
such site.
CIDR (Classless Interdomain Routing)
1. Introduce and explain CIDR (Classless Interdomain Routing).
2. Mention that it is sometimes called classless routing or supernetting.
3. Walk through an example of CIDR where a subnet boundary moves to the left.
a. Emphasize that moving the subnet boundary to the left allows an administrator
to use more bits for host information and, therefore, generate more usable IP
addresses on the network.
b. Mention that a subnet created by moving the subnet boundary to the left is
known as a supernet.
4. Use Figure 10-4 to contrast examples of a Class C supernet mask with a subnet mask.
a. In Figure 10-4, point out that 27 bits are used for network information in the
subnet mask, whereas only 22 bits are used for network information in the
supernet mask.
5. Walk through an example where an organization has leased the Class C range of IPv4
addresses that shares the network ID 199.34.89.0 and, because of growth in the
company, the network administrator needs to increase the number of host addresses this
network allows by default.
a. Use Figure 10-5 to illustrate calculating a host’s network ID on a supernetted
network.
6. Describe CIDR notation (or slash notation).
7. Define and describe a CIDR block.
8. Wrap up this topic by emphasizing that to take advantage of classless routing; a
network’s routers must be able to interpret IP addresses that do not adhere to
conventional network class parameters.
a. Routers that rely on older routing protocols, such as RIP, are not capable of
interpreting classless IP addresses.
Teaching
Tip
Point out that CIDR is pronounced cider.
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Internet Gateways
1. Define and explain a gateway.
2. Define the term default gateway.
3. Explain characteristics of default gateways.
4. Use Figure 10-6 to illustrate the use of default gateways.
5. Define and describe the advantages of a default router.
6. Describe two default gateway connections.
7. Note that routers used as gateway must maintain routing tables.
8. Describe the gateways that make up the Internet.
9. Define a core gateway.
Teaching
Tip
Student may read more about “Using Internet Gateway Device Discovery and
Control” at http://windowshelp.microsoft.com/Windows/en-US/help/670718ec7d51-49ed-87f1-b8a98ced11a41033.mspx.
Address Translation
1. Define the term public network and provide examples.
2. Define the term private network and provide examples.
3. Explain how hiding IP addresses on private networks allows network managers more
flexibility in assigning addresses.
4. Define the term NAT (Network Address Translation).
5. Describe reasons for using address translation.
6. Define and describe SNAT (Static Network Address Translation).
7. Use Figure 10-7 to illustrate SNAT.
8. Define and describe DNAT (Dynamic Network Address Translation).
9. Mention that DNAT is also called IP masquerading.
10. Define and describe PAT (Port Address Translation).
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11. Use Figure 10-8 to illustrate an example of PAT usage.
12. Explain how the gateway might instead operate on a network host.
13. Describe how in Windows operating systems, ICS (Internet Connection Sharing) can be
used to translate network addresses and allow clients to share an Internet connection.
Teaching
Tip
Student may find a “Description of Internet Connection Sharing” at
http://support.microsoft.com/kb/234815.
Quick Quiz 1
1. True or False: DHCP may be used to assign IP addresses and host names dynamically.
Answer: True
2. A node’s network ____ provides information about the segment or network to which
the node belongs.
a. frame
b. location
c. class
d. routing table
Answer: C
3. Subnetting separates a network into multiple logically defined segments, or
____________________.
Answer: subnets
4. True or False: Subnet masks are only used in IPv4 classful addressing.
Answer: False
5. A broadcast address is known as a(n) ____ address for a network or segment.
a. reserved
b. default
c. open
d. informative
Answer: A
6. True or False: In CIDR, conventional network class distinctions exist.
Answer: False
TCP/IP Mail Services
1. Explain why a student needs to understand how mail services work.
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2. Point out that all Internet mail services rely on the same principles of mail delivery,
storage, and pickup, though they may use different types of software to accomplish
these functions.
3. Explain the function of mail servers.
4. Explain the function of mail clients.
5. Emphasize that e-mail servers and clients communicate through special TCP/IP
Application layer protocols.
SMTP (Simple Mail Transfer Protocol)
1. Define and describe SMTP.
2. Point out that SMTP transports mail and holds it in a queue.
3. Mention that in Internet e-mail transmission, higher-level mail protocols such as POP
and IMAP may attempt to figure out what went wrong with an undeliverable message.
4. Describe how to configure a client to use SMPT.
Teaching Student may find more information on SMTP at
http://www.cisco.com/en/US/docs/ios/sw_upgrades/interlink/r2_0/user/ugsmtp.html.
Tip
MIME (Multipurpose Internet Mail Extensions)
1. Explain the drawbacks of SMPT.
2. Define and describe MIME as a solution to the 1000 ASCII characters limit.
a. Note that MIME is a standard for encoding and interpreting binary files, images,
video, and non-ASCII character sets within an e-mail message.
b. Point out that MIME identifies each element of a mail message according to
content type.
c. Mention that MIME encodes different content types so that SMTP is fooled into
thinking it is transporting an ASCII message stream.
3. Emphasize that MIME does not replace SMTP, but works in conjunction with it.
4. Note that most modern e-mail clients and servers support MIME.
POP (Post Office Protocol)
1. Define and describe POP.
2. Note the most current version.
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3. Describe how POP3 mail is stored and delivered.
4. Describe the advantages of using POP3.
5. Emphasize that mail is deleted from the server after it is downloaded.
a. Explain why this can be troublesome for mobile users.
IMAP (Internet Message Access Protocol)
1. Point out that IMAP is a mail retrieval protocol that was developed as a more
sophisticated alternative to POP3.
2. Describe the advantages of IMAP.
3. Describe the features of IMAP.
4. Describe the disadvantages of IMAP.
Teaching
Tip
Students may find more information on how e-mail works at
http://communication.howstuffworks.com/email.htm.
Additional TCP/IP Utilities
1. Note that there are many points of failure in a TCP transmission.
2. Explain how TCP/IP attempts to help an administrator track down most TCP/IP-related
problems without using expensive software or hardware to analyze network traffic.
3. Emphasize why students should be familiar with TCP/IP diagnostic tools.
4. Review the Telnet, ARP, and ping utilities from Chapter 4.
5. Explain the benefits of the command prompt in accessing TCP/IP utilities.
6. Note that utility command syntax may differ, depending on the client’s operating
system.
Ipconfig
1. Define and explain the ipconfig utility.
a. Review the command switches.
b. Note that this command operates with Windows-based systems.
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2. Use Figure 10-9 to illustrate the output of an ipconfig command on a Windows
Vista workstation.
Teaching
Tip
Students may find more information on the syntax and options for using the
ipconfig diagnostic utility for network connections at
http://support.microsoft.com/kb/314850.
Ifconfig
1. Define and explain the ifconfig utility.
a. Review the command switches.
b. Note that ifconfig is the UNIX and Linux version of ipconfig.
2. Use Figure 10-10 to illustrate detailed information available through ifconfig.
Teaching
Tip
Students may find more information on the syntax and options for the ifconfig
command at http://docs.sun.com/app/docs/doc/816-4554/ipconfig-141?a=view.
Netstat
1. Define and explain the netstat utility.
a. Review the command switches.
2. Use Figure 10-11 to illustrate detailed output of a netstat –a command.
Teaching
Tip
Students may read information on adding a GUI front end to the netstat command
line utility at http://articles.techrepublic.com.com/5100-10878_11-5149569.html.
Nbtstat
1. Define and explain the nbtstat utility.
a. Note that nbtstat is useful only on networks that run Windows-based operating
systems and NetBIOS.
b. Review the command switches.
Teaching
Tip
Students may find more information on nbtstat at http://technet.microsoft.com/enus/library/cc940106.aspx
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Hostname, Host, and Nslookup
1. Define and explain the hostname utility.
a. Note that the hostname utility is useful a computer running the Windows, UNIX,
or Linux operating systems.
2. Define and explain the host utility.
a. Note that Windows requires a third-party version of host.
3. Define and explain the nslookup utility.
a. Note that this utility is useful in troubleshooting DNS resolution problems.
b. Use Figure 10-12 to illustrate the result of running a simple nslookup
command at a Linux shell prompt.
c. Review how to get help with the nslookup command switches.
Dig
1. Define and explain the dig utility.
a. Compare the dig command to the nslookup command.
b. Mention that dig is useful for helping network administrators diagnose DNS
problems.
c. Point out that the dig utility is included with UNIX and Linux operating
systems.
d. Mention that for Windows-based operating system, an administrator must obtain
the code for the dig utility from a third party and install it on your system.
2. Use Figure 10-13 to illustrate the output of a simple dig command.
Whois
1. Review the basic steps that occur when a domain name is registered with ICAN.
2. Define and explain the whois utility.
a. Mention that whois utility is helpful in troubleshooting network problems.
b. Review the command syntax.
c. Mention that there are Web-based interfaces for running the whois command
Teaching
Tip
Demonstrate the use of the Whois command by navigating to
http://www.networksolutions.com/whois/index.jsp. Search for various
organizations.
Traceroute (Tracert)
1. Define and explain the traceroute utility.
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a. Note that the utility is known as tracert on Windows-based systems and
tracepath on some Linux systems.
b. Walk through the steps traceroute takes to trace the path from one networked
node to another.
c. Describe the simplest form of the traceroute command.
2. Use Figure 10-14 to illustrate output of a traceroute command.
3. Review popular switches.
Mtr (my traceroute)
1. Define and explain the mtr utility.
a. Mention that it comes with UNIX and Linux operating systems.
b. Emphasis that the mtr utility combines the functions of the ping and traceroute
utilities and delivers an easy-to-read chart as its output.
c. Describe the simplest form of the mtr command.
d. Describe some popular MTR utility switches.
2. Use Figure 10-15 to illustrate the output of the command mtr –c 100 –r
www.cengage.com
3. Describe a program similar to mtr, pathping, which is available as a command-line
utility in Windows XP, Vista, Server 2003, and Server 2008.
Route
1. Define and explain the route utility.
a. Describe the route command syntax for various operating systems and Ciscobrand routers.
2. Use Figure 10-16 to illustrate an example of a routing table.
3. Use Table 10-6 to explain the fields belonging to routing tables on UNIX or Linux
systems.
4. Review some options available for use with the route command.
5. Describe how to get help with route command options.
Quick Quiz 2
1. True or False: MIME is a standard for encoding and interpreting binary files, images,
video, and non-ASCII character sets within an e-mail message.
Answer: True
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2. True or False: The MIME standard replaces SMTP.
Answer: False
3. ____________________ is a mail retrieval protocol that was developed as a more
sophisticated alternative to POP3.
Answer: MAP (Internet Message Access Protocol), Internet Message Access Protocol,
IMAP
4. True or False: The ipconfig utility is the TCP/IP configuration and management utility
used on UNIX and Linux systems.
Answer: False
5. ____ combines the functions of the ping and traceroute utilities
a. Tracert
b. Mtr
c. Whois
d. Route
Answer: B
Class Discussion Topics
1. Discuss the benefits of subnetting.
2. Discuss why IMAP is preferred over POP3.
Additional Projects
1. Have the student research their favorite e-mail service. The students should determine
which Application layer protocols the e-mail system supports (SMTP, MIME, POP,
POP3, IMAP, etc.) and write a report on their findings. The report should also include a
description of the protocol set-up or configurations, if applicable.
2. Have student select five random companies, and issue the whois and traceroute
commands for each one. The student should prepare a report describing the results.
Require the use of screen shots to back up the reported findings.
Additional Resources
1. ARIN
https://www.arin.net/
2. SMTP
http://www.cisco.com/en/US/docs/ios/sw_upgrades/interlink/r2_0/user/ugsmtp.html
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3. IMAP
http://www.imap.org
4. RFC 1009 Requirements for Internet Gateways (Historic)
http://tools.ietf.org/html/rfc1009
5. RFC 5034 The Post Office Protocol (POP3)
http://tools.ietf.org/html/rfc5034
Key Terms
 ANDing - A logical process of combining bits. In ANDing, a bit with a value of 1 plus another
bit with a value of 1 results in a 1. A bit with a value of 0 plus any other bit results in a 0.
 CIDR (Classless Interdomain Routing) - An IP addressing and subnetting method in which
network and host information is manipulated without adhering to the limitations imposed by
traditional network class distinctions. CIDR is also known as classless routing or supernetting.
Older routing protocols, such as RIP, are not capable of interpreting CIDR addressing schemes.
 CIDR block - In CIDR notation, the number of bits used for an extended network prefix. For
example, the CIDR block for 199.34.89.0/22 is /22.
 CIDR notation - In CIDR, a method of denoting network IDs and their subnet boundaries.
Slash notation takes the form of the network ID followed by a slash ( / ), followed by the
number of bits that are used for the extended network prefix.
 classful addressing - An IP addressing convention that adheres to network class distinctions, in
which the first 8 bits of a Class A address, the first 16 bits of a Class B address, and the first 24
bits of a Class C address are used for network information.
 Classless Interdomain Routing - See CIDR.
 classless routing - See CIDR.
 core gateway - A gateway that operates on the Internet backbone.
 default gateway - The gateway that first interprets a device’s outbound requests, and then
interprets its inbound requests to and from other subnets. In a Postal Service analogy, the
default gateway is similar to a local post office.
 default router - See default gateway.
 dig (domain information groper) - A TCP/IP utility that queries the DNS database and
provides information about a host given its IP address or vice versa. Dig is similar to the
nslookup utility, but provides more information, even in its simplest form, than nslookup can.
 DNAT (Dynamic Network Address Translation) - A type of address translation in which a
limited pool of Internet-valid IP addresses is shared by multiple private network hosts.
 domain information groper - See dig.
 Dynamic Network Address Translation - See DNAT
 extended network prefix - The combination of an IP address’s network ID and subnet
information. By interpreting the address’s extended network prefix, a device can determine the
subnet to which an address belongs.
 host - A TCP/IP utility that at its simplest returns either the IP address of a host if its host name
is specified or its host name if its IP address is specified.
 hostname - A TCP/IP utility used to show or modify a client’s host name.
 ICS (Internet Connection Sharing) - A service provided with Windows 98, Me, 2000 and 32bit versions of XP operating systems that allows one computer, the ICS host, to share its
Internet connection with other computers on the same network.
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 ICS host - On a network using the Microsoft Internet Connection Sharing service, the computer
whose Internet connection other computers share. The ICS host must contain two network
interfaces: one that connects to the Internet and one that connects to the LAN.
 IMAP (Internet Message Access Protocol) - A mail retrieval protocol that improves on the
shortcomings of POP. The single biggest advantage IMAP4 has relative to POP is that it allows
users to store messages on the mail server, rather than always having to download them to the
local machine. The most current version of IMAP is version 4 (IMAP4).
 IMAP4 (Internet Message Access Protocol, version 4) - The most commonly used form of
the Internet Message Access Protocol (IMAP).
 Internet Connection Sharing - See ICS.
 Internet Message Access Protocol - See IMAP.
 Internet Message Access Protocol, version 4 - See IMAP4.
 IP masquerading - See DNAT.
 MIME (Multipurpose Internet Mail Extensions) - A standard for encoding and interpreting
binary files, images, video, and non-ASCII character sets within an e-mail message.
 mtr (my traceroute) - A route discovery and analysis utility that comes with UNIX and Linux
operating systems. Mtr combines the functions of the ping and traceroute commands and
delivers an easily readable chart as its output.
 Multipurpose Internet Mail Extensions - See MIME.
 NAT (Network Address Translation) - A technique in which IP addresses used on a private
network are assigned a public IP address by a gateway when accessing a public network.
 nbtstat - A TCP/IP troubleshooting utility that provides information about NetBIOS names and
their addresses. If you know the NetBIOS name of a workstation, you can use nbtstat to
determine its IP address.
 NetBIOS - A protocol that runs in the Session and Transport layers of the OSI model and
associates NetBIOS names with workstations. NetBIOS alone is not routable because it does not
contain Network layer information. However, when encapsulated in another protocol such as
TCP/IP, it can be routed.
 netstat - A TCP/IP troubleshooting utility that displays statistics and the state of current TCP/IP
connections. It also displays ports, which can signal whether services are using the correct ports.
 Network Address Translation - See NAT.
 network number - See network ID.
 network prefix - See network ID.
 nslookup - A TCP/IP utility that allows you to look up the DNS host name of a network node
by specifying its IP address, or vice versa. This ability is useful for verifying that a host is
configured correctly and for troubleshooting DNS resolution problems.
 PAT (Port Address Translation) - A form of address translation that uses TCP port numbers
to distinguish each client’s transmission, thus allowing multiple clients to share a limited
number of Internet-recognized IP addresses.
 pathping - A command-line utility that combines the functionality of the tracert and ping
commands (similar to UNIX’s mtr command) and comes with Windows XP, Vista, and
Windows Server 2003 and Server 2008.
 POP (Post Office Protocol) - An Application layer protocol used to retrieve messages from a
mail server. When a client retrieves mail via POP, messages previously stored on the mail
server are downloaded to the client’s workstation, and then deleted from the mail server.
 POP3 (Post Office Protocol, version 3) - The most commonly used form of the Post Office
Protocol.
 Port Address Translation - See PAT.
 Post Office Protocol - See POP.
 Post Office Protocol, version 3 - See POP3.
 private network - A network whose access is restricted to only clients or machines with proper
credentials.
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 public network - A network that any user can access with no restrictions. The most familiar
example of a public network is the Internet.
 route - A utility for viewing or modifying a host’s routing table.
 Simple Mail Transfer Protocol - See SMTP.
 slash notation - See CIDR notation.
 SMTP (Simple Mail Transfer Protocol) - The Application layer TCP/IP subprotocol
responsible for moving messages from one e-mail server to another.
 SNAT (Static Network Address Translation) - A type of address translation in which each
private IP address is correlated with its own Internet-recognized IP address.
 Static Network Address Translation - See SNAT.
 supernet - A type of subnet that is created using bits that normally would be reserved for
network class information - by moving the subnet boundary to the left.
 supernet mask - A 32-bit number that, when combined with a device’s IP address, indicates the
kind of supernet to which the device belongs.
 supernetting - See CIDR.
 tracepath - A version of the traceroute utility found on some Linux distributions.
 traceroute (tracert) - A TCP/IP troubleshooting utility that uses ICMP to trace the path from
one networked node to another, identifying all intermediate hops between the two nodes.
Traceroute is useful for determining router or subnet connectivity problems. On Windows-based
systems, the utility is known as tracert.
 whois - The utility that allows you to query ICANN’s DNS registration database and find
information about a domain.