CIS 1140 Network Fundamentals

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27 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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CIS 1140 Network Fundamentals

Chapter Four: Introduction to TCP/IP
Protocols

Collected and Compiled

By JD Willard

MCSE, MCSA, Network+,

Microsoft IT Academy Administrator

Computer Information Systems Instructor

Albany Technical College

Attention: Accessing Demos


This course presents many demos.


The Demos

require that you be logged in to the Virtual
Technical College web site when you click on them to run.


To access and log in to the Virtual Technical College web site:


To access the site type
www.vtc.com

in the url window


Log in using the username: CIS 1140 or ATCStudent1


Enter the password: student (case sensitive)



If you should click on the demo link and you get an Access
Denied it is because you have not logged in to vtc.com or you
need to log out and log back in.


If you should click on the demo link and you are taken to the
VTC.com web site page you should do a search in the search
box for the CompTIA Network+ (2009 Objectives) Course and
run the video from within that page.


Objectives


Identify and explain the functions of the core TCP/IP protocols


Explain the TCP/IP model and how it corresponds to the OSI
model


Discuss addressing schemes for TCP/IP in IPv4 and IPv6
protocols


Discuss addressing schemes for TCP/IP in IPv4 and IPv6 and
explain how addresses are assigned automatically using
DHCP (Dynamic Host Configuration Protocol)


Describe the purpose and implementation of DNS (Domain
Name System)


Identify the well
-
known ports for key TCP/IP services


Describe how common Application layer TCP/IP protocols are
used

Network Protocols


A Protocol is a set of standards or rules that governs how
networks communicate


Protocols often provide services, such as e
-
mail or file
transfer. Most protocols are not intended to be used alone,
but instead rely on and interact with other dependent or
complimentary protocols


Protocols vary according to their purpose, speed,
transmission efficiency, utilization of resources, ease of setup,
compatibility, and ability to travel between different LANs.


Multiprotocol networks: networks running more than one
protocol


A group of protocols that is intended to be used together is
called a

protocol suite


Most popular protocol suite is TCP/IP


Others: IPX/SPX, NetBIOS, and AppleTalk

Network Protocols Defined
Demo


Transport Protocols
Demo


Understanding Network Protocols
Demo


Characteristics of TCP/IP (Transmission
Control Protocol/Internet Protocol)


TCP/IP is not one protocol but a suite of specialized protocols called
subprotocols.


Subprotocols include TCP, IP, UDP, ARP, ICMP, IGMP etc.


Developed by US Department of Defense


ARPANET (1960s)


Internet precursor


Advantages of TCP/IP


Open nature


Costs nothing to use


Flexible


Runs on virtually any platform


Connects dissimilar operating systems and devices


Routable


Transmissions carry Network layer addressing information


Suitable for large networks

Overview
Demo

Introduction
Demo


TCP IP Basics
Demo


TCP/IP Compared to the OSI Model


The TCP/IP suite of protocols can be divided into four layers that
roughly correspond to the seven layers of the OSI Model.





Application layer



The Application layer corresponds to the Session,
Presentation, and Application layers of the OSI model. Applications gain
access to the network through this layer, via protocols such as the File
Transfer Protocol (
FTP
), Trivial File Transfer Protocol (
TFTP
), Hypertext
Transfer Protocol (
HTTP
), Simple Mail Transfer Protocol (
SMTP
), and
Dynamic Host Configuration Protocol (
DHCP
).




Transport layer



This layer comparable to the Transport layer of the
OSI model and contains the Transmission Control Protocol (
TCP
) and User
Datagram Protocol (
UDP
), which provide flow control, error checking, and
sequencing. All service requests use one of these protocols.




Internet layer



This layer is comparable to the Network layer of the OSI
model contains the Internet Protocol (
IP
), Internet Control Message Protocol
(
ICMP
), Internet Group Message Protocol (
IGMP
), and Address Resolution
Protocol (
ARP
). These protocols handle message routing and host address
resolution.




Network access layer (or Link layer)


This layer corresponds to the
functions of the Physical and Data Link layers of the OSI mode and is
responsible for describing the physical layout of the network and how
messages are formatted and transmitted to the network wire.




TCP/IP and OSI Models

Demo



The TCP/IP Model (5:00)

The TCP/IP model compared with the OSI model

The TCP/IP Suite
Demo


The TCP/IP Suite
Demo

continued


The TCP/IP Suite
Demo

continued


The TCP/IP Core Protocols


TCP/IP suite subprotocols


Operate in Transport or Network layers of
OSI model


Provide basic services to protocols in
other layers


Most significant protocols in TCP/IP suite


TCP


IP

Networking Protocols (6:17)

TCP/IP Suite Basics
Demo

TCP (Transmission Control Protocol)


Transport layer protocol that operates host to
host.


Provides reliable data delivery services


Connection
-
oriented subprotocol


Establish connection before transmitting


Uses sequencing and acknowledgements


Provides flow control


TCP segment format


Encapsulated by IP packet in Network layer


Becomes IP packet’s “data”

Understanding TCP
Demo

Transmission Control Protocol
Demo


Connection Controls and Windowing

Demo

A TCP segment


TCP (cont’d.)


The TCP three
-
way handshake is
the process used to establish a
TCP session.


The steps to a TCP three
-
way
handshake process are:

1.
A host sends a SYN packet to
the target host.

2.
The target host responds to
the original host with a SYN
ACK packet.

3.
The host responds to the
target host with an ACK
packet.

Establishing a TCP connection

UDP (User Datagram Protocol)


Transport layer protocol


Provides unreliable data delivery services


Connectionless transport service


No assurance packets received in correct sequence


No guarantee packets received at all


Best effort delivery


No error checking, sequencing


Lacks sophistication


More efficient than TCP


Useful when large amounts of data need to be
transferred quickly such as with live audio and video
transmissions over the Internet.

Understanding UPD
Demo

13

A UDP segment

UDP (User Datagram Protocol)

IP (Internet Protocol)


Network layer protocol


How and where data delivered, including:


Data’s source and destination addresses


Addressing schemes: uses an IP address, such as 10.1.1.1 and a
Subnet Mask such as 255.0.0.0


Enables TCP/IP to internetwork


Traverse more than one LAN segment


More than one network type through router


Routing: Statically and Dynamically via many routing protocols;
OSPF, BGP, RIP and EIGRP


Network layer data formed into packets


IP packet


Data envelope that contains information for routers to transfer
data between different LAN segments


Unreliable, connectionless protocol


Relies on upper layer protocols like TCP to ensure delivery and connection
orientation

TCP/IP
Demo

Pt.2

Internet Protocol
Demo


Understanding IP
Demo

IP Packet


IP datagram: packet,
in context of TCP/IP


Envelope for data


IP adds the following
header fields to each
packet:


Source IP
Address


Destination IP
Address


Protocol


Checksum


Time to Live (TTL)


An IPv4 packet

IGMP


Operates at the Network layer of the OSI model and is a
protocol for defining host groups


Manages multicasting on networks running IPv4


Allows one node to send data to a defined group of
nodes


Similar to broadcast transmission


All group members can receive broadcast messages
intended for the group (called multicasts)


Multicast groups can be composed of devices within the
same network or across networks (connected with a
router)


Point
-
to
-
multipoint method


Used for Internet teleconferencing or
videoconferencing

Understanding IGMP
Demo

ARP (Address Resolution Protocol )


Network layer protocol used with IPv4 that
provides IP
address
-
to
-
MAC address name address resolution


Obtains MAC (physical) address of host or node


A host wishing to obtain a physical address broadcasts an
ARP request onto the TCP/IP network. The host on the
network that has the IP address in the request then replies
with its physical hardware address.


Creates database that maps MAC to host’s IP address


ARP table (ARP Cache)


Table of recognized MAC
-
to
-
IP address mappings


Saved on computer’s hard disk


Increases efficiency


Contains dynamic and static entries

ARP (4:02)

Understanding ARP
Demo

ICMP (Internet Control Message Protocol)


ICMP is commonly used for troubleshooting and information
gathering. ICMP allows you to test the path (among other
things). Ping and Tracert are two tools that can be used to
test a path and they both use ICMP. ICMP packets will be
able to help send information about errors, control, and other
informational messages.


Network layer protocol


Reports on data delivery success/failure


Announces transmission failures to sender


Network congestion


Data fails to reach destination


Data discarded: TTL expired


ICMP cannot correct errors


Provides critical network problem troubleshooting
information


ICMPv6 used with IPv6


Understanding ICMP
Demo

Connectivity Parameters

The following table summarizes the configuration settings required to connect
to a TCP/IP network.


Parameter

Purpose

IP address

The IP address Identifies both the logical host and the logical network addresses.


Each host on the entire network must have a unique IP address.


Two devices on the same subnet must have IP addresses with the same network
portion of the address.


Two devices on the same subnet must have unique host portions of the IP address.


Do not use the first or the last host address on a subnet address range.

Subnet mask

The subnet mask identifies which portion of the IP address is the network address, and
which portion is the host address. Two devices on the same subnet must be configured
with the same subnet mask.

Default gateway

The default gateway identifies the router to which communications for remote networks
are sent. The default gateway address is the IP address of the router interface on the
same subnet as the local host. Without a default gateway set, most clients will be unable
to communicate with hosts outside of the local subnet.

DNS server

The DNS server address identifies the DNS server that is used to resolve host names to
IP addresses.

Host name

The host name identifies the logical name of the local system.

IP Addressing Overview

IP Addressing
Demo

Pt.1


IP Addressing
Demo

Pt.2


IP Addresses
Demo

Addressing in TCP/IP



Networks recognize two addresses


Logical (Network layer)


Physical (MAC, hardware) addresses


IP protocol handles logical addressing


Specific parameters


Unique 32
-
bit number


Divided into four octets (sets of eight bits) separated
by periods


Example: 144.92.43.178


Network class determined from first octet




What is an IP Address?

Demo


IP Address

Demo


Adding Protocols

Demo


Binary and Dotted Decimal Notation


Dotted decimal notation


Common way of expressing IP addresses


Decimal number between 0 and 255 represents each octet


Period (dot) separates each decimal


Each number in dotted decimal address has binary equivalent


Convert each octet


Remove decimal points


Base 2 Numbering is Binary


Consists of ‘0’ and ‘1’. Bits are either “Off” (0) or “On” (1)


Computers like Binary!


IP Addresses are comprised of four 8 bit octets that are expressed as a
decimal number between 0 and 255 separated by a period

Bit Value 128 64 32 16 8 4 2 1

Bit



1 0 1 1 0 0 1 1 = 128+32+16+2+1=179


A Binary Lesson
Demo


Solutions for Binary
Demo


Binary Addressing

Demo


Binary Math (7:59)

Binary to Decimal Conversions

Bit Number:

8

7

6

5

4

3

2

1

Binary Equiv:

2
7

2
6

2
5

2
4

2
3

2
2

2
1

2
0

Decimal Equiv:

128

64

32

16

8

4

2

1


Binary Number:

1

0

0

1

1

1

0

1

Decimal Equiv:

128+

0+

0+

16+

8+

4+

0+

1=







157


1) Determine what decimal numbers in the table will create the number you
want to make.

2) Enter a “1” under each value you must use. Enter a “0” for each value
that is not used in the Binary Number line.

3) The resulting combination of 0’s and 1’s is the binary equivalent of the
number.

Sample Binary to Decimal Conversion

Convert Decimal 5 to Binary


Bit Number:

8

7

6

5

4

3

2

1

Binary Equiv:

2
7

2
6

2
5

2
4

2
3

2
2

2
1

2
0

Decimal Equiv:

128

64

32

16

8

4

2

1

Binary Number:

0

0

0

0

0

1

0

1


4) Determine what decimal numbers in the table will create the decimal
number 5
(4+1).

5) The resulting combination of
00000101

is the binary equivalent of the
decimal number 5.

Address Classes


There are three primary classes of network addresses:
A, B, and C.


The actual class used is based on the size of the
network.


An IP address is accompanied by a subnet mask.


Each address class has a different default subnet mask.


IP addresses are expressed in dotted
-
decimal format,
such as 192.168.123.132.


Each set of four dotted
-
decimal numbers represents
eight bits of the binary address.


The addresses range from 00000000 to 11111111,
or, in decimal notation, from 0 to 255.


Address Classes

Demo


IP Classes (9:52)

IP Address Classes
Demo

Classful Addressing


Adheres to network class distinctions


Only Class A, B, and C addresses are recognized


Network ID limited to first 8 bits in Class A, first 16 bits
in Class B, and first 24 bits in Class C


Fixed network ID size ultimately limits number of hosts a
network can include



First Octet
1
-
126


First Octet
128


191


First Octet
192
-

223

Components of an IP Address
Demo


Classful Addressing


IPv4 addresses have a default

class
. The address class identifies
the range of IPv4 addresses. The following table shows the default
address class for each IPv4 address range.


Class

First Octet
Range

Number of
Networks

Maximum Addressable
Hosts
per Network

A

1
-
126


126

(1.0.0.0
to
126.0.0.0)

16,777,214

(1.0.0.1
to
1.255.255.254)

B

128
-
191


16,384

(128.1.0.0
to
191.255.0.0)

65,534

(128.1.0.1
to
128.1.255.254)

C

192
-
223


2,097,152

(192.0.1.0
to
223.255.255.0)

254

(192.168.1.1
to
192.168.1.254)

Reserved Addresses


Certain types of IP addresses reserved for special
functions


Network ID Cannot Be 127


127 is reserved for lookback functions


Network ID and Host ID Cannot Be 255 (All Bits Set to 1)


In broadcast addresses, octet(s) representing host information
set to all 1s (255 in decimal notation)


255 is a broadcast address


Network ID and Host ID Cannot Be 0 (All Bits Set to 0)


In network IDs, bits for host information set to 0


0 means “this network only”


Host ID Must Be Unique to the Network


IP Address Rules

Demo

Addressing in TCP/IP


ipconfig: Windows NT, XP, Vista, 2000, 2003, 2008 command to
view IP information


Winipcfg: Win98, ME


ifconfig on Unix

and Linux



/all
switch

IPConfig,Ifconfig, Winipcfg
Demo

Results of the
ipconfig /all

command on a
Windows XP or Windows Vista workstation

Ipconfig
Demo


What Is a Subnet Mask?


In binary form, the subnet mask is always a series of 1's followed by a series
of 0's (1's and 0's are never mixed in sequence in the mask). A simple mask
might be 255.255.255.0.


Distinguishes the Network ID from the Host ID


Combines with device IP address to mask the Network ID with all 1s


Informs network about segment, network where device attached


Used to specify
w
hether the destination host is local or remote (
ANDing
)


Four octets (32 bits)


Expressed in binary or dotted decimal notation


Assigned same way as IP addresses


Manually or automatically (via DHCP)


Subnet Masks
Demo

Subnet Mask
Demo

Subnet Masks


Every device on TCP/IP
-
based network identified by subnet mask


32
-
bit number that, when combined with device’s IP address,
informs rest of network about segment or network to which a
device is attached


Subnetting, subdividing single class of networks into multiple,
smaller logical networks or segments, depends on subnet masks to
identify how a network is subdivided


Indicates where network information is located in an IP address


“1” bits indicate corresponding bits in IP address contain network
information


“0” bits indicate corresponding bits in IP address contain host
information


To calculate host’s network ID given IP address and subnet mask,
perform ANDing

Subnet Masks

Demo



Solutions for Masks

Demo



Anding IP Addresses
Demo


Default Subnet Masks (No Subnetting)

Bits Used for Subnet Mask

Address

Class

Dotted Decimal

Notation

Class A

Class B

Class C

11111111

00000000

00000000

00000000

11111111

11111111

00000000

00000000

11111111

11111111

11111111

00000000

255.0.0.0

255.255.0.0

255.255.255.0

Class B Example

16.200

131.107.

0.0

255.255.

131.107.

w.x.

IP Address

Subnet Mask

Network ID

Host ID

16.200

y.z

IPv6 Addressing


Composed of
128
bits


Eight 16
-
bit fields


Typically represented in hexadecimal numbers


Separated by a colon


Example: FE22:00FF:002D:0000:0000:0000:3012:CCE3


Abbreviations for multiple fields with zero values


00FF can be abbreviated FF


0000 can be abbreviated 0


Multicast address


Used for transmitting data to many different devices simultaneously


Anycast

address


Represents any one interface from a group of interfaces


Modern devices and operating systems can use both IPv4 and IPv6


IPv6 Basics
Demo

IPv4 and IPv6 (5:18)

Why IPv6?
Demo

ADDRESS ASSIGNMENT

IP Address Assignment
Demo

Pt.1


Configure TCP/IP
Demo


Because IP addresses assigned to hosts must be unique, the use of IP
addresses on the Internet is controlled by organizations that ensure that
no two organizations are given the same range of IP addresses to assign
to hosts.


The Internet Assigned Numbers Authority (IANA) manages the
assignment of IP addresses on the Internet. IANA is operated by the
Internet Corporation for Assigned Names and Numbers (ICANN).


IANA allocates blocks of IP addresses to Regional Internet Registries
(RIRs). An RIR has authority for IP addresses in a specific region of the
world.


An RIR assigns a block of addresses to Internet Service Providers
(ISPs).


An ISP assigns one or more IP addresses to individual computers or
organizations connected to the Internet.


On private networks IP addresses are assigned to computers either
manually, called static addressing, or automatically through a DHCP
server which is called dynamic address allocation.

DHCP (Dynamic Host Configuration
Protocol)


Automatically assigns device a unique IP address


Application layer protocol


Reasons for implementing



Reduce time and planning for IP address management


Reduce potential for error in assigning IP addresses


Enable users to move workstations and printers


Make IP addressing transparent for mobile users


DHCP leasing process


Device borrows (leases) an IP address while attached to network


Lease time


Determined when client obtains IP address at log on


User may force lease termination


DHCP service configuration


Specify leased address range


Configure lease duration


Several steps to negotiate client’s first lease


Dynamic Clients

Demo

Dynamic Addressing
Demo

DHCP Leasing Process


Device borrows (leases) an IP address while
attached to network


Lease
time


Determined
when client obtains IP address at log
on


User may force lease
termination


ipconfig

/release


DHCP service configuration


Specify leased address range


Configure lease duration


Several steps to negotiate client’s first lease



DHCP Leasing Process


The client goes through a four stage broadcast based process to
obtain an IP Address lease from a DHCP server.


Step 1: Upon bootup the client sends out a
DHCPDISCOVER

packet in
broadcast fashion to discover the identity and whereabouts of all DHCP
servers on the broadcast segment.


Step 2: Upon receiving the broadcast any DHCP servers on that
broadcast segment will respond with their own
DHCPOFFER

packet.


Step 3: The client will accept the first offer received and respond with a
DHCPREQUEST

broadcast. Other DHCP servers who have made an
offer hear this broadcast and return their IP address to the pool.


Step 4: The chosen DHCP server responds with an
DHCPACK

confirming the clients acceptance of the IP lease along with additional
information such as subnet mask, default gateway and DNS server.

DHCP Addressing Overview (4:35)

DHCP Leasing Process

DHCP Lease Process
Demo


DHCP in a Routed Environment
Demo


DHCPDISCOVER

BROADCAST


DHCPOFFER

BROADCAST


DHCPREQUEST

BROADCAST


DHCPACK

BROADCAST


IP Lease Renewal

DHCP Leases (4:24)

Terminating a DHCP Lease


Lease expiration


Automatic


Established in server configuration


Manually terminated at any time


Client’s TCP/IP configuration


Server’s DHCP configuration


Circumstances requiring lease termination


DHCP server fails and replaced


Windows: release of TCP/IP settings


DHCP services run on several server types


Installation and configurations vary

Private Addresses


Private addresses


Allow hosts in organization to communicate across internal network


Cannot be routed on public network


Specific IPv4 address ranges reserved for private addresses


10.0.0.0
-

10.255.255.255
-

Addresses: 16,777,216


172.16.0.0
-

172.31.255.255
-

Addresses: 1,048,576


192.168.0.0
-

192.168.255.255
-

Addresses: 65,536


The private addressing works well for allowing computers to access
resources inside the private network only


Routers inside the private network can route traffic between private addresses with no
trouble.


To access the Internet, or a public network, computers have to have a
public address. This is where Network Address Translation (NAT)
comes into play.


Routers on the Internet will not accept IP addresses in a private IP address range


Special Addresses
Demo

Link
-
Local Addresses

APIPA (Automatic Private IP Addressing)


Link
-
local address


Provisional address


Capable of data transfer only on local network segment


APIPA is a Microsoft implementation of automatic IP address assignment without
a DHCP server. Using APIPA, hosts assign themselves an IP address on the
169.254.0.0 network (mask of 255.255.0.0). With APIPA:


The host is configured to obtain IP information from a DHCP server (this is
the default configuration).


If a DHCP server can't be contacted, the host uses APIPA to assign itself an
IP address.


The host only configures the IP address and mask. It does not assign itself
the default gateway and DNS server addresses. For this reason, APIPA can
only be used on a single subnet
.


Disadvantage


Computer only communicates with other nodes using addresses in APIPA
range


IP Address Assignment
Demo

Pt.2


APIPA (3:42)

Static (manual) Assignment


Using static addressing, IP configuration information
must be manually configured on each host. Use static
addressing:


On networks with a very small number of hosts.


On networks that do not change often or that will not grow.


To permanently assign IP addresses to hosts that must always
have the same address (such as printers, servers, or routers).


For hosts that cannot accept an IP address from DHCP.


To reduce DHCP
-
related traffic.


Static addressing is very susceptible to configuration
errors and duplicate IP address configuration errors.


Static addressing disables both APIPA and DHCP
capabilities on the host.

Static Addressing
Demo

Static Clients

Demo

Ports and Sockets


Ports

are logical connections, provided by the TCP or UDP protocols at the
Transport layer, for use by protocols in the upper layers of the OSI model.
TCP/IP uses port numbers stored in the header of a packet to determine
what protocol incoming traffic should be directed to.


Every process on a machine assigned a port number 0 to 65535


Process’s port number plus host machine’s IP address equals process’s
socket

Example:
10.216.5.1:53


Ensures data transmitted to correct application


Well Known Ports: in range 0 to 1023


Assigned to processes that only the OS or system administrator can
access


Registered Ports: in range 1024 to 49151


Accessible to network users and processes that do not have special
administrative privileges


Dynamic and/or Private Ports: in range 49152 through 65535


Open for use without restriction


Common TCP and UDP Ports (8:09)

Understanding Port Numbers
Demo

Sockets and Ports


Commonly used TCP/IP port numbers

Well Known Port Numbers
Demo

Name Resolution Overview

NetBIOS Name Resolution
Demo


Resolving a Host Name

Demo


DHCP/ DNS/WINS Servers
Demo


Name Resolution Overview
Demo


TCP/IP addressing


Long, complicated numbers


Good for computers


People remember words better


Internet authorities established Internet node naming
system


Host


Internet device


Host name


Name describing device


Every host can take a host name


Host Names and DNS (Domain Name System)

Host Naming
Demo


Domain Names


Domain


Group of computers belonging to same organization


Share common part of IP address


Domain name


Identifies domain (loc.gov)


Associated with company, university, government organization


Fully qualified host name (blogs.loc.gov)


Local host name plus domain name


Label (character string)


Separated by dots


Represents level in domain naming hierarchy


Example:
www.google.com


Top
-
level domain (TLD): com


Second
-
level domain:
google


Third
-
level domain: www


Second
-
level domain


May contain multiple third
-
level domains


ICANN established domain naming conventions


Domain names must be registered with an Internet naming authority that works on
behalf of ICANN


What is DNS?

Demo


Domain Names (cont’d.)


ICANN approved over 240 country codes


Host and domain names restrictions


Any alphanumeric combination up to 253 characters


Include hyphens, underscores, periods in name


No other special characters

Structure of DNS
Demo


Host Files


ARPAnet used HOSTS.TXT file


Associated host names with IP addresses


Host matched by one line


Identifies host’s name, IP address


Alias provides nickname


UNIX
-
/Linux
-
based computer


Host file called hosts, located in the /etc directory


Windows computer


Host file called hosts


Located in Windows
\
system32
\
drivers
\
etc folder

Host Name Resolution
Demo


DNS (Domain Name System)


Hierarchical method of associating domain names with IP addresses


Refers to Application layer service that accomplishes association and
organized system of computers and databases making association
possible


DNS redundancy


Many computers across globe related in hierarchical manner


Root servers


13 computers (ultimate authorities)


Three components


Resolvers


Any hosts on Internet needing to look up domain name information


Name servers (DNS servers)


Databases of associated names, IP addresses


Provide information to resolvers on request


Namespace


Abstract database of Internet IP addresses, associated names


Describes how name servers of the world share DNS information


The DNS Namespace

Demo

Root Domain Name Servers
Demo


An Overview of DNS (8:12)

DNS Resource Records


Entries for hostnames, IP addresses, and other information in the zone database are
stored in
records
. Each host has at least one record in the DNS database that maps the
hostname to the IP address. The following table lists common resource records.


The A record maps an IPv4 (32
-
bit) DNS host name to an IP address. This is the most
common resource record type.


The AAAA record maps an IPv6 (128
-
bit) DNS host name to an IP address.


The CNAME record provides alternate names (or aliases) to hosts that already have a
host record. Using a single A record with multiple CNAME records means that when
the IP address changes, only the one A record needs to be modified.


The MX record identifies servers that can be used to deliver e
-
mail.


The PTR record maps an IP address to a host name (i.e. "points" to an A record).


DNS Records
Demo


DNS Records (9:05)

Domain Name Space


The Domain Name System (DNS) is a hierarchical, distributed database that maps
logical host names to IP addresses. The DNS hierarchy is made up of the following
components:


. (dot) domain (also called the

root
domain)


Top Level Domains (TLDs) such as .com, .edu, .gov


Additional domains such as yahoo.com, microsoft.com, etc.


Hosts


The fully
-
qualified domain name (FQDN) includes the host name and all domain
names, separated by periods. The final period (for the root domain) is often omitted
and implied.


DNS Resolution Process

Resolving www.microsoft.com

Name Resolution
Demo

1.
The client looks in its local cache to see if it has recently
resolved the host name.

o
If the information is not in the cache, it checks the
Hosts file.

o
If the IP address is not found, the host contacts its
local DNS server. If the local DNS server can't be
contacted, it continues contacting additional DNS
servers until one responds.

o
The client sends the name information to the DNS
server.

2.
The DNS server then checks its cache and Hosts file. If
the information is not found, the DNS server checks any
zone files that it holds for the requested name.

o
If the DNS server can't find the name in its zones, it
forwards the request to a root zone server. This
server returns the IP address of a DNS server that
has information for the corresponding top
-
level
domain (such as .com).

3.
The local DNS server then requests the information from
the top
-
level domain server. This server returns the
address of a DNS server with the information for the next
highest domain (Microsoft).

4.
The local DNS server then requests the information from
the Microsoft DNS server which holds the necessary
information. This server returns the address of the
requested host name.

5.
The local DNS server places the information in its cache
and returns the IP address to the client.

6.
The client host also places the information in its cache
and uses the IP address to contact the desired destination
device.

DDNS (Dynamic DNS)


Dynamic DNS (DDNS) enables clients or the DHCP server to update
records in the zone database.


Without dynamic updates, all A (host) and PTR (pointer) records must
be configured manually. With dynamic updates, records are created and
deleted automatically.


Dynamic DNS is required to support Active Directory.


A dynamic update occurs when a client modifies its corresponding
resource record on the DNS server.


Dynamic updates occur when:


A network connection's IP address is added, deleted, or changed.


The DHCP server changes or renews an IP address lease.


The client's DNS information is manually changed using
ipconfig
/registerdns
.


The client boots.


A server is promoted to a domain controller.


Integrating DHCP DDNS
Demo


Dynamic DNS (4:26)

Application Layer Protocols


Work over TCP or UDP plus IP


Translate user requests into format readable by network


HTTP


HTTP is used by Web browsers and Web servers to exchange files
(such as Web pages) through the World Wide Web and intranets


HTTPS is a secure form of HTTP that uses SSL to encrypt data before it
is transmitted.


DHCP


DHCP is a method for automatically assigning addresses and other
configuration parameters to network hosts.

Other Protocols Built on TCP/IP
Demo


Management Protocols (10:51)

Application Protocols (9:36)

Understanding HTTP
Demo

Telnet


Terminal emulation protocol


Log on to remote hosts


Using TCP/IP protocol suite


TCP connection established


Keystrokes on user’s machine act like
keystrokes on remotely connected machine


Often connects two dissimilar systems


Can control remote host


Drawback


Notoriously insecure

The Concept of Telnet
Demo

FTP (File Transfer Protocol)


FTP provides a generic method of transferring files


Send and receive files via TCP/IP


FTP can transfer both binary and text files, including HTML, to
another host


Host running FTP server portion


Accepts commands from host running FTP client


FTP commands


Operating system’s command prompt


No special client software required


FTP hosts allow anonymous logons


Secure FTP (SFTP)


More secure version of FTP


SFTP uses Secure Shell (SSH) to secure data transfers.


SSH ensures that SFTP transmissions use encrypted
commands and data which prevent data from being transmitted
over the network in clear text.

Understanding FTP & TFTP
Demo

SFTP
Demo

TFTP (Trivial File Transfer Protocol)


Enables file transfers between computers


Simpler (more trivial) than FTP


TFTP is faster than FTP, but might be subject to file
errors


TFTP relies on Transport layer UDP


Connectionless


No error correction and does not guarantee reliable
data delivery


No ID or password required


Security risk


No directory browsing allowed


Useful to load data, programs on diskless workstation


Often used when transferring files such as video,
audio, or images

NTP (Network Time Protocol)


NTP is used to communicate time synchronization
information between systems on a network


Depends on UDP Transport layer services


Benefits from UDP’s quick, connectionless nature


Time sensitive


Cannot wait for error checking


Time synchronization importance


Routing


Time
-
stamped security methods


Maintaining accuracy, consistency between multiple
storage systems

PING (Packet Internet Groper)


Provides verification


TCP/IP installed, bound to NIC, configured
correctly, communicating with network


Host responding


Uses ICMP services


Send echo request and echo reply messages


Determine IP address validity


Ping IP address or host name


Ping loopback address: 127.0.0.1


Determine if workstation’s TCP/IP services
running

Ping (5:16)

PING (cont’d.)


Operating system determines PING command
options, switches, syntax



Output from successful and unsuccessful PING

Ping
Demo


Summary


Protocols define the standards for communication
between nodes on a network


TCP/IP is most popular protocol suite, because of its low
cost, open nature, ability to communicate between
dissimilar platforms, and routability


TCP provides reliability through checksum, flow control,
and sequencing information


IP provides information about how and where data
should be delivered


Every IP address contains two types of information:
network and host

Summary (continued)


Subnetting is implemented to control network traffic and
conserve a limited number of IP addresses


Dynamic IP address assignment can be achieved using
BOOTP or the more sophisticated DHCP


A socket is a logical address assigned to a specific
process running on a host


IPv6 provides several other benefits over IPv4


A domain is a group of hosts that share a domain name
and have part of their IP addresses in common


DNS is a hierarchical way of tracking domain names and
their addresses


The End