Lecture

A+ Lesson Plan Week 12 Addendum


Networking


I. Why do we network?


Cost

Share Resources

Increase Productivity


2. History

Arpanet – Milnet – Internet

Networking careers – Network technician, Network architect, network   administrator, network Analyst


3. Network Types

Centralized – Mainframe

Peer to peer

Client/server


Geographical types

LANs

WANs


4. Architectural Topologies

Bus, star, ring, mesh


5. Network models – protocols


OSI, TCP/IP SNA

IP, IPX, NetBIOS, netbui, DDP (AppleTalk)

Applications – HTTP, SMTP, SNAP, FTP, Telnet


6. Network Devices

Hubs, repeaters, bridges, switches, routers, gateways (same as router), Nic cards

Cabling – coax, thinnet, thicknet fiber, copper twisted pair UTP STP

Wireless – RF, IR, microwave










IP Addressing


IP Addressing can be very complicated. Here, we will just get into the addressing basics and a little bit of Subnetting. The lecture will begin with a review of binary, octal, and hexadecimal numbering systems.


NOTE: It has been my experience that this subject is only useful to these students during this class. Many of their mathematically skills in understand more in depth coverage of Subnetting is over their heads.


There are three classes of IP addressing. They are made up of 32 bit and expressed as decimal dot notation (ex. 207.30.101.234). There are four sets (octets) of three hexadecimal numbers. There are five classes of IP addresses.


Class A – 1st octet is the network portion – the rest are the host addresses

Network #’s from 1 – 126 – max # of hosts = 17 million (3 Octets)

Ex. nnn.hhh.hhh.hhh

Class B – 1st and 2nd octets are network addresses – the rest are host addresses

Network #’s from 128 – 191 – Max # of hosts – 65600 Max # of networks – 16400


Note: 127.0.0.x is a special reserved address (actually the address of loop back on your Nic cards)

Ex. nnn.nnn.hhh.hhh

Class C – 1st, 2nd, and 3rd Octets are network portion – the rest are host addresses

Network #’s from 193 – 254 – Max # of nets 268.5 million – max # of hosts – 254


Note: 192.168.0.x reserved for private use


Class D – under development

Class E – not yet exist

Ex. nnn.nnn.nnn.hhh

Addresses cannot be all 0’s or all 1’s. All 1’s are called a broadcast address and they are specifically banned due to the network traffic of broadcast storms. If you have a computer with the address of all 1’s – it would answer every packet and resend all packets to everyone.


Subnetting


When you get an IP Address you will receive a Class C number. This gives you 254 possible hosts but the average number in use is only 10 of those hosts. Since the world is running out of networking numbers, you use Subnetting to re-use the same numbers throughout the network. Basically, Subnetting is the addition of a second IP Address – in the same format but with different meanings for the bits. The subnet mask defines how many of the original IP Address are actually network versus host bits. The subnet mask breaks down the assigned number of hosts from 254 to some number of hosts. It accomplishes this be defining some of the normal host bits in a class C network as network numbers and not hosts (ex. nnn.nnn.nnn.nnhh).

A default subnet mask exists for each class of IP Address. The defaults are as follows,

Class A – 255.0.0.0

Class B – 255.255.0.0

Class C – 255.255.255.0


Using some number other than 0 in the last octets above is Subnetting – exchanging some host numbers for net numbers.

Some of the more well known and common subnet numbers are


2 bits – 192 Ex. in binary – nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh

3 bits – 224 Ex. in binary – nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh

4 bits – 240 Ex. in binary – nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh

5 bits – 248 Ex. in binary – nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh

6 bits – 252 Ex. in binary – nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh


The computer uses the Boolean process called Anding to calculate which part of the host addresses is to be converted into the network address.


IPv4 and IP v6


Since the world is running out of IP numbers, they have gone to IP v 6 that uses a 64 bit address instead of IPv4 which uses only 32 bits. This is currently in place on the backbone infrastructure between major portals but not yet implemented on your home computer. It is similar to the post offices use of extended zip codes. XP has the capability of using IPv6.


Explain

Alpha testers – test version 1 of something

Beta testers test version 1.x and above

Charter testers – report back to creator any bugs that are found.


Well known ports


Routers also use ports to identify which program is the originator or recipient of a packet on the network. Some well known ports are

80 for http

21 ftp

23 telnet

25 SMTP

110 pop3

161 SNMP

194 IRC