Data Communication
IOS110 I & J
Week 3
Fall 2011
Communication
• Both Servers and Clients require guidelines that permit
communication across a network
• The language used by computers are called Protocols
Protocol guidelines consist of the following:
1) How data that is formatted into Packets and Frames
2) How packets and frames are sent across the network
3) How packets and Frames are handled at the receiving end
Transmitting Data
Ethernet
• Ethernet is a standard communications protocol embedded in
software and hardware devices, intended for building a Local
Area Network (LAN).
• Frames travel within Ethernet, sent from one computer and
received by one or more computers, within a LAN
• Frames contain Packets of Data
• Data traveling through the Internet begin and end within
Ethernet connections.
• Ethernet is simple to maintain, reliable and low cost
Transmitting Data
Packets and Frames
http://www.highteck.net/EN/Ethernet/Ethernet.html
Transmitting Data
Transmission Control Protocol/Internet Protocol (TCP/IP)
• TCP/IP is the communication protocol for the internet.
• TCP/IP defines how computers should connect to the Internet
and how data is transmitted between them
• Inside the TCP/IP standard there are additional protocols for
handling data communication:
– TCP (Transmission Control Protocol) communication between
applications
– IP (Internet Protocol) communication between computers
Transmitting Data
Transmission Control Protocol
• Applications (browsers, e-mail) use TCP to begin and end
transmissions to the Internet
• TCP ensures data is sent in the correct format and sequence and
that received data is reassembled in the correct sequence
• TCP is Connection-Oriented-Communication
Internet Protocol (IP)
• IP handles routing of packets (Source IP, Destination IP, Sequence
number, time-to-live, etc)
• Packets can pass through Routers that re-send data to final
destination. Several routers may be involved (hops) ***.
• Does not perform error checking (TCP does that)
• IPv4 and IPv6 are two versions of IP
***http://www.yougetsignal.com/tools/visual-tracert/
IP Classes
There are three common classes available for IP addressing (IPv4). They are;
Class A.
The first octet (10.X.X.X) denotes the network address, and the last three
octets are the host portion. Any IP address whose first octet is between 1
and 126 is a class A address. (126 networks/16,777,214 addresses per
network)
Class B.
The first two octets (130.10.X.X) denote the network address, and the last
two octets are the host portion. Any address whose first octet is in the
range 128 to 191 is a class B address. (16,384 networks/65,532 addresses
per network)
Class C.
The first three octets (198.50.125.X) denote the network address, and the last
octet is the host portion. The first octet range of 192 to 223 is a class C
address. (2,097,152 networks/254 addresses per network)
What address range is missing from class A?
Look at class A and B for a clue.
IP Classes
Each IP Class contains a group of address that are intended for a private
networks (non-routable IP’s).
Class A.
10.0.0.0–10.255.255.255. A single class A network
Class B.
172.16.0.0–172.31.255.255. A group of 16 contiguous class B Networks
Class C.
192.168.0.0–192.168.255.255. A contiguous group of 256 class C networks
If these are private addresses, how do we access the Internet?
Net Address Translation (NAT)
NAT translation is accomplished from with a router, that tracks the tracks
the private IP address of the computer sending or receiving data.
Note the additional identifier added to the source IP address. NAT
adds this number so that it can send data back to the proper IP
address when data is returned to the private network.
Reading
• Complete reading of chapter 1. You are responsible for the
entire chapter.
• Begin reading chapter 2.