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 Frames2) How packets and frames are sent across the network3) 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 DataTransmission 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 ClassesThere 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.