Transcript Slide 1

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
Understanding Network Protocols Demo
Transport Protocols Demo
Characteristics of TCP/IP (Transmission
Control Protocol/Internet Protocol)
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•
•
•
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
Introduction Demo
Overview 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.
The TCP/IP Model (5:00)
TCP/IP and OSI Models Demo
The TCP/IP model compared with the OSI model
The TCP/IP Suite Demo continued
The TCP/IP Suite Demo
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
TCP/IP Suite Basics Demo
Networking Protocols (6:17)
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
A TCP segment
Transmission Control Protocol Demo
Connection Controls and Windowing Demo
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
UDP (User Datagram Protocol)
A UDP segment
13
IP (Internet Protocol)
Understanding IP Demo
• 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
Internet Protocol Demo
TCP/IP Demo Pt.2
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)
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•
•
•
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
The IP address Identifies both the logical host and the logical network addresses.
IP address
Subnet mask

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.
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 Addresses Demo
IP Addressing Demo Pt.1
IP Addressing Demo Pt.2
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
IP Address Demo
What is an IP Address? Demo
Adding Protocols Demo
Binary and Dotted Decimal Notation
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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
Binary Math (7:59)
Binary Addressing Demo
A Binary Lesson Demo
Solutions for Binary Demo
Binary to Decimal Conversions
Bit Number:
8
Binary Equiv: 27
Decimal Equiv: 128
7
26
64
6
25
32
5
24
16
4
23
8
3
22
4
2
21
2
1
20
1
Binary Number: 1
Decimal Equiv: 128+
0
0+
0
0+
1
16+
157
1
8+
1
4+
0
0+
1
1=
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
Binary Equiv: 27
Decimal Equiv: 128
Binary Number: 0
7
26
64
0
6
25
32
0
5
24
16
0
4
23
8
0
3
22
4
1
2
21
2
0
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.
1
20
1
1
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.
IP Address Classes Demo
IP Classes (9:52)
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
A
B
C
First Octet
Range
1-126
128-191
192-223
Number of
Networks
126
(1.0.0.0 to
126.0.0.0)
16,384
(128.1.0.0 to
191.255.0.0)
2,097,152
(192.0.1.0 to
223.255.255.0)
Maximum Addressable Hosts
per Network
16,777,214
(1.0.0.1 to 1.255.255.254)
65,534
(128.1.0.1 to 128.1.255.254)
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 Demo
Results of the ipconfig /all command on a
Windows XP or Windows Vista workstation
IPConfig,Ifconfig, Winipcfg Demo
What Is a Subnet Mask?
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•
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 whether 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 Mask Demo
Subnet Masks 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)
Address
Class
Bits Used for Subnet Mask
Dotted Decimal
Notation
Class A
11111111
00000000 00000000 00000000
255.0.0.0
Class B
11111111
11111111
00000000 00000000
255.255.0.0
Class C
11111111
11111111
11111111
255.255.255.0
00000000
Class B Example
IP Address
131.107. 16.200
Subnet Mask
255.255. 0.0
Network ID
131.107. y.z
Host ID
w.x. 16.200
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
IPv4 and IPv6 (5:18)
Why IPv6? Demo
IPv6 Basics Demo
ADDRESS ASSIGNMENT
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.
Configure TCP/IP Demo
IP Address Assignment Demo Pt.1
DHCP (Dynamic Host Configuration
Protocol)
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•
•
•
•
•
•
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
Dynamic Addressing Demo
Several steps to negotiate client’s first lease
Dynamic Clients 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
DHCP Addressing Overview (4:35)
• 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 Leasing Process
DHCPDISCOVER
BROADCAST
DHCPREQUEST
BROADCAST
DHCP Lease Process Demo
DHCPOFFER
BROADCAST
DHCPACK
BROADCAST
DHCP in a Routed Environment Demo
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
APIPA (3:42)
IP Address Assignment Demo Pt.2
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
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•
•
•
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
Understanding Port Numbers Demo
Common TCP and UDP Ports (8:09)
Sockets and Ports
Well Known Port Numbers Demo
Commonly used TCP/IP port numbers
Name Resolution Overview
Name Resolution Overview Demo
NetBIOS Name Resolution Demo
Resolving a Host Name Demo
DHCP/ DNS/WINS Servers Demo
Host Names and DNS (Domain Name System)
• 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 Naming Demo
Domain Names
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•
•
•
•
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)
An Overview of DNS (8:12)
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•
•
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
Root Domain Name Servers Demo
• 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
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 (9:05)
DNS Records Demo
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
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.
Resolving www.microsoft.com
Name Resolution Demo
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.
Dynamic DNS (4:26)
Integrating DHCP DDNS Demo
Application Layer Protocols
Management Protocols (10:51)
Application Protocols (9:36)
•
•
•
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.
Understanding HTTP Demo
DHCP
– DHCP is a method for automatically assigning addresses and other
configuration parameters to network hosts.
Other Protocols Built on TCP/IP 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
Ping Demo
Output from successful and unsuccessful PING
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