Transcript Document

Chapter Eleven
An Introduction to TCP/IP
Objectives
• To compare TCP/IP’s layered structure to OSI
• To review the structure of an IP address
• To look at some of the different protocols in the
suite
• To learn a bit about address translation in
TCP/IP
TCP/IP and Layers
• TCP/IP has four layers
– Compared to OSI’s seven layers
• For the most part, map cleanly to OSI layers
The Four TCP/IP Layers
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Process/Application
Host-to-Host
Internet
Network Access
Mapping TCP/IP Layers to OSI
Application
Process Application
Presentation
Session
Host to Host
Transport
Internet
Network
Network Access
Data Link
Physical
Reviewing IP Address Structure
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IPv4 uses a 32-bit address.
IPv6 uses a 128-bit address.
IPv4 addresses are broken down into classes.
One address identifies both the network and
host address.
• A subnet mask separates the network portion
from the host portion of the address.
IP Address Classes
• Class A
– 1 octet for network, 3 for host
• Class B
– 2 octets for network, 2 for host
• Class C
– 3 octets for network, 1 for host
• Class D – multicasts
• Class E – experimental
TCP/IP Protocol Suite
• Different protocols work at different layers.
• Different functions exist at each protocol layer.
• No protocols exist at the Network Access layer
that I will discuss here.
Process Application Protocols
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FTP/TFTP
HTTP
Telnet
SMTP/POP
IMAP4
SNMP
NFS
FTP/TFTP
• File Transfer Protocol/Trivial File Transfer
Protocol
– Both function to transfer complete files over the
network
– FTP is a connection-oriented protocol
• Port 20 for user data and Port 21 for control data
– TFTP is a connectionless protocol
• Port 69 for user data, no control data passed
HTTP and HTTPS
• Hypertext Transfer Protocol and Hypertext
Transfer Protocol Secure
– Used for interpreting and moving hypermedia
over a network
– HTTP uses Port 80; HTTPS uses Port 443.
– HTTPS uses the secure socket layer (SSL) and
encryption algorithms in order to increase
security.
Telnet
• Creates a virtual terminal on the network
• Allows a user to take control of a device
remotely
• Uses Port 23
• Used by many routers and switches for
configuration
SMTP and POP
• The protocols of email
– Simple Mail Transfer Protocol for outgoing
– Post Office Protocol for incoming
• SMTP uses Port 25
• POP3 uses Port 110 (older POP2 uses 109)
IMAP4
• Internet Message Access Protocol, Version 4
• A more advanced protocol for sending email
messages
• Allows users to create and maintain folders on
the remote server
• Uses Port 220
SNMP
• Simple Network Management Protocol
– Allows network administrators to gather
information about the network and to perform
routine maintenance functions remotely
– SNMP manager runs on the administrator
machine and the agent on the user’s machine
– Uses Port 161 for general messages and 162 for
trap messages
NFS
• Network File System
– Allows the network to be browsed like a disk
drive
– Uses Port 2049
Host-to-Host Protocols
• TCP
• UDP
• DNS
TCP
• Transmission Control Protocol
– Manages point-to-point movement of data from
source to target
– Connection-oriented protocol
– Handles flow control, multiplexing, data transfer,
and error correction/detection
UDP
• User Datagram Protocol
• Connectionless protocol
• Useful for broadcast messages and/or small
data packages
DNS
• Domain Name Services
– Resolves Internet domain names to IP
addresses
– Acts as the core protocol for active directory
Structure of a DNS Domain Name
• The “dot” server
– .com, .gov, .org and so on and so forth
– The dot points to the DNS root.
– A different set of servers, called root servers, maintains database of
each type of DNS root.
• The top level domain
– Country code (.us, .uk, .jp, and so forth)
– Generic domains (.com, .gov, .biz, and so forth)
– Infrastructure domains (.arpa) the address routing domain
DNS at Work
• Each workstation must be configured with the address
of a DNS server.
• You type in a universal resource locator (URL) and
your computer can’t resolve it.
• The request is forwarded to the DNS server configured
in TCP/IP.
• If the DNS server has no record, it forwards the
request to the appropriate root server.
Types of DNS Query
• Recursive
– If the DNS server cannot resolve the request, it will
forward it to the next level.
– When the next level replies, the server adds the
information to its database.
• Iterative
– The request MUST be fulfilled on the local server.
– It responds with all it knows and that’s all she wrote.
Internet Layer Protocols
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IP
BootP
DHCP
ICMP
ARP
RARP
IP
• Handles addressing between different networks
• Provides for fragmentation of data over a
network connection
• Handles all routing functions
• Tracks packet time to live
BootP
• It allows a computer to boot up using files that
are stored on a remote device.
• The bootstrap loader directs its boot request to
the boot PROM on the NIC.
• The request is forwarded through Port 67.
• A BootP server sends back a boot reply packet
with the data it needs to locate the boot files.
DHCP
• Dynamic Host Configuration Protocol
– It configures a client computer with all of its
TCP/IP information.
– This information is “leased” for a certain time.
– DHCP can configure IP address, subnet mask,
DNS server, and several other items.
ICMP
• Internet Control Message Protocol
– Announces network errors
– Announces conditions of network congestion
– Announces when a packet has timed out
– Is the core protocol for PING
ARP
• Address Resolution Protocol and Reverse
Address Resolution Protocol
– ARP sends out a packet to the target device
requesting a reply.
– The reply has the machine’s IP address and
MAC address in the header.
RARP
• It requires that RARP server be configured.
• A client machine broadcasts its IP address.
• The RARP server responds with an IP address.
Address Resolution in TCP/IP
• WINS
• HOSTS
• LMHOSTS
WINS
• Windows Internet Name Service
– Resolves a NetBIOS name to an IP address
– Requires that a WINS server be configured on
the network
– Is old and graying, but not dead just yet
The HOSTS and LMHOSTS File
• Both are text files stored in the root directory.
• HOSTS maps a DNS name to an IP address.
• LMHOSTS maps a NetBIOS name to an IP
address.