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IST 201
Chapter 9
TCP/IP Model
Application
Transport
Internet
Network Access
Application Layer Protocols
FTP
TFTP
NFS
SMTP
Application
Telnet
Rlogin
SNMP
Transport
DNS
HTTP
Internet
Network Access
Transport Layer Protocols
Application
Transport
Internet
Network Access
TCP
UDP
Internet Layer Protocols
Application
Transport
Internet
Network Access
IP
ICMP
ARP
RARP
Network Access
Application
Transport
Internet
Network Access
Ethernet
Fast Ethernet
SLIP & PPP
FDDI
ATM, Frame Relay, SMDS
ARP
Proxy ARP
RARP
TCP
• Segments upper layer application data
• Sends segments from one end device to
another
• Establishes end to end operations
• Flow control
• Reliability – sequence #’s &
acknowledgements
• Error detection & correction
Three-way Handshake
Has a
message to
send
Sending host/node
TCP three-way handshake to
establish a logical communication
connection. Communication can
begin once the handshake is
complete. A three-way
handshake is also used to end the
connection.
Receiving host/node
IP
• Defines a packet & address scheme
• Transfers data between Internet layer and
network access
• Connectionless
Network Access
•
•
•
•
Software & drivers for NIC, ISDN & modems
Mapping IP addresses to MAC addresses
Encapsulating packets into frames
Defines the connection with the medium
TCP/IP Model v. OSI
Application
Presentation
Application
Transport
Session
Transport
Network
Internet
Data Link
Network Access
Physical
TCP/IP & OSI Similarities
• Layers
• Packet switched
TCP/IP & OSI Differences
• TCP/IP Model combines first three layers of
OSI
• TCP/IP Model combines data link & phys into
network access
• TCP/IP – simpler
• TCP/IP – internet was built based on it
• OSI – guide for understanding communication
process
Internet Architecture
• Getting messages from one network to another requires
different approaches than getting messages from one host to
another on a LAN
• Internetworking – building networks of networks
•
•
•
•
•
•
must be scalable - # networks & computers
transport data vast distances
flexible for technological changes
dynamic
cost effective
anytime, anywhere communication
IANA
• Internet Assigned Numbers Authority
• organization that assigns network addresses
• duplicate public addresses not allowed
• organizations may obtain IP network address from an
ISP for $
IP Addressing
Unique
address
• IP address for each node must be unique
• Four bytes (bytes called octets)
• 10.9.19.3 might be a node address
• 10.0.0.0 would be the network address
• The first 10 in 10.9.19.3 corresponds to the network in this
example.
• Subnet mask identifies which part of the IP address
refers to the network address and which part to the
node.
• 11111111.00000000.00000000.00000000 (binary subnet mask)
• 255.0.0.0 would be the subnet mask
IP Address Classes
• Businesses are assigned network IP addresses
by IANA depending on the size of the business.
• Class A – very large businesses such as the
US government
• Class B – large businesses
• Class C – medium sized businesses
IP Class Addresses and Subnet
Masks
• The first number of the network address
identifies the network class
• Class A: 1 – 126
• S/N mask: 255.0.0.0
• Class B: 128 – 191
• S/N mask: 255.255.0.0
• Class C: 192 – 223
• S/N mask: 255.255.255.0
127 used for
loopback address
(troubleshooting)
Private addresses
•
•
•
•
10.0.0.0
172.16.0.0
192.168.0.0
May only be used internally.
ICMP
• Internet Control Message Protocol
• Ping and Tracert are two utilities that use ICMP.
• Provides control and error messaging
capabilities.
Proposed Solutions to Too Few
IPv4 Network Addresses
• CIDR (classless interdomain routing)
• Single IP address can represent many IP addresses
• Example: 172.200.0.0/16
• Private addressing internally
• Using NAT (network address translation) to map external
public address to internal private addresses
• IPv6
Proxy ARP
• If a host wants to communicate with a host that
is not in the same network, the router can be
configured to provide it’s own MAC address if
the destination host address is not in the MAC
table.
• This process allows the message to leave and
re-enter the network via the router.
Default Gateway
• Configured router interface that is used to
communicate with hosts outside the current
segment (network).
• Router sends it’s own MAC address.
Static v. DHCP Addresses
• Static address – manually assigned by the
network administrator
• DHCP – dynamic host configuration protocol
• Dynamically (automatically) assigns IP addresses to
hosts on the network for some predetermined
amount of time.