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Basic Networking
Network models are as follows:
- Peer-to-Peer - A peer to peer network is one in which lacks a dedicated server and every computer acts as both a client and a server. This is a good networking solution when there are 10 or less users that are in close proximity to each other. A peer to peer network can be a security nightmare, because the people setting permissions for shared resources will be computer idiots and the right people will never have access to the right resources. Thus is only recommended in situations where security is not an issue.
- Client/Server - This type of network is designed to support a large Number of users and uses dedicated server/s to accomplish this. Clients log on to the server/s in order to run applications or obtain files. Security and permissions can be managed by 1 or more administrators which cuts down on the aforementioned computer illiterates from medling with things that they shouldn't be. This type of network also allows for convenient backup services, reduces network traffic and provides a host of other services that come with the network operating system(NOS).
Local Area Networks
A local area network (LAN) is a high-speed communications system designed to link computers and other devices together within a small geographic area, such as a workgroup, department, or a building. There are several different types of common networks listed below:
| Network Type |
Cabling |
Connector |
Maximum Length |
Speed |
| 10Base5 |
RG-8 or RG-11, Thicknet coax |
AUI/DIX |
500 meters(1640 ft) |
10 mbps |
| 10Base2 |
RG-58, thinnet coax |
BNC connector |
185 meters(607 ft) |
10 mbps |
| 10BaseT |
Cat 3, 4, 5, 5e, 6 twisted pair |
RJ-45 |
100 meters(328 ft) |
10 mbps |
| 100Base-TX |
Cat 5, 5e, 6 twisted pair |
RJ-45 |
100 meters(328 ft) |
100 mbps |
| 100Base-FX |
Fiber Optic |
ST, SC |
2 Kilometers(6562 feet) |
200 mbps |
| 1000Base-T - Gigabit Ethernet |
CAT 5e, 6, Fiber |
RJ-45 |
100 meters(328 ft) |
1 gbps |
| 802.11b |
Wireless / WiFi |
No cabling. Uses Access Point (AP) for connection |
150+ feet |
11 mbps |
| 802.11g |
Wireless / WiFi |
No cabling. Uses Access Point (AP) for connection |
150+ feet |
54 mbps |
| Infrared |
N/A |
No cabling. Uses direct line of sight connections |
Varies |
Up to 16 mbps |
Additional Notes: Infrared technologies vary widely. They can be used for transmitting data between PDAs or cell phones. This technology typically connects at a speed of about 115 kbps while advanced technologies for connecting 2 networks together between buildings can run as high as 10 gbps and extend several miles. Windows XP supports VFIR (Very Fast Infrared) which can transmit at up to 16Mbps.
Remote Access
For the purposes of the A+ exam, you will need to be familiar with the following methods of connecting to the internet:
| Network Type |
Speed |
Cabling |
Description |
| Dial-up connection (POTS) |
Up to 56 Kbps |
Twisted pair |
Rapidly being replaced by faster technologies. |
| Integrated Services Digital Network (ISDN) |
128 kbps |
Coaxial cable |
Business access |
| Digital Subscriber Line (DSL) |
256 Kbps to 8 Mbps |
Twisted-pair |
Home, small business, and enterprise access using existing phone lines. |
| Cable modem |
512 Kbps to 52 Mbps |
Coaxial cable |
Home, business, school access |
| Satellite |
400 kbps |
Satellite Dish |
Rural and remote areas |
Additional Notes:
Dial-up networking is fading away with the adoption of faster technologies.
ISDN service is an older, but still viable technology offered by phone companies in some parts of the U.S.. ISDN requires an ISDN adapter instead of a modem, and a phone line with a special connection that allows it to send and receive digital signals.
ADSL allows you to connect to the internet via your phone line, but allows you to use your phone while connected to the internet. Unlike a cable modem, the speed is stable.
Cable modems are much faster generally than ADSL, however, your mileage will vary depending on how many other people are using the bandwidth on your segment.
Satellite connections come in two types - 1-way and 2-way. 1-way satellites only accept signals and 2-way connections send and receive. Satellite connections can be affected by weather.
Cabling
This next table lists the transmission speeds of the various cable types.
| Transmission Medium |
Transmission Speed |
| Thicknet |
10 mbps |
| Thinnet |
10 mbps |
| cat 2 twisted pair |
4 mbps |
| cat 3 twisted pair |
10 mbps |
| cat 4 twisted pair |
16 mbps |
| cat 5 twisted pair |
100 mbps |
| cat 5e twisted pair |
1 gbps |
| cat 6 twisted pair |
10 gbps |
| Fiber Optic |
100 mbps - 1 gbps |
| 802.11b |
11 mbps |
| 802.11g |
54 mbps |
Miscellaneous Cable Info
Shielded twisted pair (STP) differs from UTP in that it has a foil jacket that helps prevent crosstalk. Crosstalk is signal overflow from an adjacent wire. STP can support speeds up to 20 mbps.
Plenum grade cabling is required if the cabling will be run between the ceiling and the next floor (this is called the plenum). Plenum grade cabling is resistant to fire and does not emit poisonous gasses when burned. PVC cable, while cheaper, will emit poisonous gases in extreme heat or fire.
Thicknet is often used as a backbone. A transceiver with a vampire tap penetrates the core of the cable. From the transceiver a DB-15 connector plugs into the AUI port on a given device.
Token ring networks can use UTP and STP cabling. Older versions used IBM-type Data Connector (IDC) and Universal Data Connectors (UDC). These 2 types of cabling are now obselete.
Fiber Optic cabling has an built in security as you can't intercept data as you can with other cable mediums.
Protocols
Protocols are the special set of rules that end points use in a telecommunication connection when they communicate. These rules allow computers with dissimilar operating sytems, network topologies, hardware, etc. to communicate. Next is a description of some of the more common protocols:
- TCP/IP - TCP/IP is the protocol suite of the internet and will be covered in the next section.
- IPX/SPX - These protocols were developed by Novell and are/were used with Novell Netware. IPX is the fastest routable protocol and is not connection oriented. IPX addresses are up to 8 characters in hexadecimal format. SPX is connection oriented.
- NetBeui - Stands for "NetBIOS Extended User Interface". It is the standard protocol used by Microsoft's operating systems. It is NetBEUI that allows the "shares' between machines. In reference to the NetBIOS distinction, NetBIOS is the applications programming interface and NetBEUI is the transport protocol. NetBEUI is a non-routable protocol meaning it will not allow communication through a router.
- Appletalk - AppleTalk is the name given to the set of protocol and networking standards created by Apple Computer for use with the Macintosh family of computers. AppleTalk is routable and automatically handles such things as assigning of workstation and network addresses, message routing between networks, etc.
TCP/IP
TCP/IP Protocol Suite
The TCP/IP protocol suite is made of many other protocols that perform different functions. Below is a list of some of them:
- TCP - TCP breaks data into manageable packets and tracks information such as source and destination of packets. It is able to reroute packets and is responsible for guaranteed delivery of the data.
- IP - This is a connectionless protocol, which means that a session is not created before sending data. IP is responsible for addressing and routing of packets between computers. It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layer protocols such as TCP.
- ICMP - Internet Control Message Protocol enables systems on a TCP/IP network to share status and error information such as with the use of PING and TRACERT utilities.
- SMTP - Used to reliably send and receive mail over the Internet.
- FTP - File transfer protocol is used for transferring files between remote systems. Must resolve host name to IP address to establish communication. It is connection oriented (i.e. verifies that packets reach destination).
- ARP - provides IP-address to MAC address resolution for IP packets. A MAC address is your computer's unique hardware number and appears in the form 00-A0-F1-27-64-E1 (for example). Each computer stores an ARP cache of other computers ARP-IP combinations.
- POP3 - Post Office Protocol. A POP3 mail server holds mail until the workstation is ready to receive it.
- TELNET - Provides a virtual terminal or remote login across the network that is connection-based. The remote server must be running a Telnet service for clients to connect.
- HTTP - The Hypertext Transfer Protocol is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. It is the protocol controlling the transfer and addressing of HTTP requests and responses.
TCP/IP Ports
Ports are what an application uses when communicating between a client and server computer. Some common ports are:
- 21 FTP
- 23 TELNET
- 25 SMTP
- 80 HTTP
- 110 POP3
TCP/IP Addressing
Every IP address can be broken down into 2 parts, the Network ID(netid) and the Host ID(hostid). All hosts on the same network must have the same netid. Each of these hosts must have a hostid that is unique in relation to the netid. IP addresses are divided into 4 octets with each having a maximum value of 255. We view IP addresses in decimal notation such as 124.35.62.181, but it is actually utilized as binary data.
IP addresses are divided into 3 classes as shown below:
| Class |
Range |
| A |
1-126 |
| B |
128-191 |
| C |
192-223 |
NOTE: 127.x.x.x is reserved for loopback testing on the local system and is not used on live systems. The following address ranges are reserved for private networks:
10.0.0.0 - 10.254.254.254
172.16.0.0 - 172.31.254.254
192.168.0.0 - 192.168.254.254
IPv6
The previous information on TCP/IP has referred to IPv4, however, this addressing scheme has run out of available IP addresses due to the large influx of internet users and expanding networks. As a result, the powers that be had to create a new addressing scheme to deal with this situation and developed IPv6. This new addressing scheme utilizes a 128 bit address (instead of 32) and utilizes a hex numbering method in order to avoid long addresses such as 132.64.34.26.64.156.143.57.1.3.7.44.122.111.201.5. The hex address format will appear in the form of 3FFE:B00:800:2::C for example.
Wireless Networking
As the name implies, wireless networks allow computers to comunicate without the use of cables. IEEE 802.11b defines two pieces of equipment, a wireless station, which is usually a PC or a Laptop with a wireless network interface card (NIC), and an Access Point (AP),which acts as a bridge between the wireless stations and Distribution System (DS) or wired networks. An 802.11b wireless network adapter can operate in two modes, Ad-Hoc and Infrastructure. In infrastructure mode, all your traffic passes through a wireless ‘access point’. In Ad-hoc mode your computers talk directly to each other and do not need an access point at all. 802.11b delivers data throughput of 11 Mbps.
Network Cards
A Network Interface Card, often abbreviated as NIC, is an expansion board you insert into a computer so the computer can be connected to a network. Like other expansion cards, network cards require that the appropriate driver is loaded to function properly. If a network card will not function it may be due to an IRQ or memory conflict. Typical settings for these are:
- IRQ - 5
- Port Address - 300h
- Base Memory - D8000h
Modern network cards can run in full-duplex mode which means that they send and receive data at the same time. You can see this occurring by looking at the RX and TX (receive and transmit) LEDs on the back of a network card. Older network cards only supported half-duplex and could only send or receive, but not both at the same time.
Further Reference:
http://www.techtutorials.com/Networking/
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