Modern Communication Services

Modern Communication Services

Society is becoming more informationally and visually oriented every day. Personal computing facilitates easy access, manipulation, storage, and exchange of information. These processes require reliable transmission of data information. Communicating documents by images and the use of high resolution graphics terminals provide a more natural and informative mode of human interaction than just voice and data. Video teleconferencing enhances group interaction at a distance. High definition entertainment video improves the quality of picture at the expense of higher transmission bit-rates, which may require new transmission means other than the present overcrowded radio spectrum. A modern Telecommunications network (such as the broadband network) must provide all these different services (multi-services) to the user.
Differences between traditional (telephony) and modern communication services

Conventional telephony communicates using:

* the voice medium only
* connects only two telephones per call
* uses circuits of fixed bit rate

In contrast, modern communication services depart from the conventional telephony service in these three essential aspects. Modern communication services can be:

* Multimedia
* point to point, and
* multi-rate

These aspects are examined Individually in the following three sub-sections.

* Multi-media: A multi-media call may communicate audio, data, still images, or full-motion video, or any combination of these media. Each medium has different demands for communication qualities, such as:
o bandwidth requirement
o signal latency within the network, and
o signal fidelity upon delivery by the network

Moreover, the information content of each medium may affect the information generated by other media. For example, voice could be transcribed into data via voice recognition and data commands may control the way voice and video are presented. These interactions most often occur at the communication terminals, but may also occur within the network .

* Multi-point: A multi-point call involves the setup of connections among more than two people. These connections can be multi-media. They can be one way or two way communications. These connections may be reconfigured many times within the duration of a call. A few examples will be used to contrast point-to-point communications versus multi-point communications. Traditional voice calls are predominantly two party calls, requiring a point-to-point connection using only the voice medium. To access pictorial information in a remote database would require a point-to-point connection that sends low bit-rate queries to the database, and high bit-rate video from the database. Entertainment video applications are largely point-to-multi-point connections, requiring one way communication of full motion video and audio from the program source to the viewers. Video teleconferencing involves connections among many parties, communicating voice, video, as well as data. Thus offering future services requires flexible management of the connection and media requests of a multi-point, multi-media communication call .
* Multi-rate A multi-rate service network is one which allocates transmission capacity flexibly to connections. A multi-media network has to support a broad range of bit-rates demanded by connections, not only because there are many communication media, but also because a communication medium may be encoded by algorithms with different bit-rates. For example, audio signals can be encoded with bit-rates ranging from less than 1 kbit/s to hundreds of kbit/s, using different encoding algorithms with a wide range of complexity and quality of audio reproduction. Similarly, full motion video signals may be encoded with bit-rates ranging from less than 1 Mbit/s to hundreds of Mbit/s. Thus a network transporting both video and audio signals may have to integrate traffic with a very broad range of bit-rates.

BASICS OF NETWORKING

BASICS OF NETWORKING

Networking is connecting two or more devices to allow communication between them with the purpose of sharing information and resources. Examples of these devices are computers, printers, routers, hubs, modems, and PDAs. The information and resources being shared can be anything from MS Office documents and e-mail to printers and fax devices. Internetworking is connecting multiple networks with the purpose of creating one large network. The Internet is the most common example of an internetwork.

Client/server vs Peer-to-peer

Most of today's networks use the client/server model. In this model at least one computer acts as a server. Servers hold resources that are accessed over the network by clients. Examples of resources are shared files, e-mail messages and even applications. Another common server is the print server that allows access to network printers.
In a peer-to-peer network model every computer can act as a client and a server at the same time. An example is a network with 4 Windows XP Professional computers in a workgroup using file and print sharing.

LAN/WAN

The terms LAN and WAN mainly refer to the geographical area of the network. LAN is short for Local Area Network and is a high-speed network typically within a building. WAN is short for Wide Area Network and refers to low-speed networks that cover a large distance, for example a network that spans several cities or the entire globe even. The Internet can be considered the largest WAN, but actually consists of many different WANs, which, in turn, include LANs. The connection between LANs in an internetwork is also referred to as a WAN connection, although a network diagram of a WAN often includes the LANs in it.

Private vs Public Networks

Two other terms used to categorize networks are private networks and public networks. A private network is typically within the premises of a corporation and can be accessed only by users working for, or related to, that corporation. A public network Internet can be accessed by multiple individuals and/or corporations, the best example of a public network is again, the Internet.

Media

The physical connection used to transport electrical signals (bits; 1s & 0s) between the network devices is called the media. Examples of network media are copper cabling, fiber optic cabling and infra-red.

Protocols

To be able to communicate with each other, network devices need a common language. The language network devices use is called a protocol. There are many different types of protocols available, and most protocols are actually a suite of several protocols, each with a different function. For example, one protocol allows data transfer between hosts and another can be used to retrieve email from a mail server.

Addressing

If you want to contact somebody by snail-mail or by telephone you need some sort of address. In a telephone network you need to enter a telephone number to reach your intended communication partner. Similar, devices in a network need an address. There are two types of addresses, the first type is configured in software by a network administrator and uses protocols to define the addressing scheme and format, this type is known as network or layer 3 addressing. The other type of address that devices in a network use, is most commonly referred to as MAC address; this address is burned into the chip of the physical network interface.

Network Topologies

A physical topology depicts how network devices are connected physically, the cabling.
A logical topology depicts the route a the signal takes on the network.
Collisions

A collision indicates that two or more network nodes have tried to access the network simultaneously, and both put a signal on the network cable at the same time which collide with each other. Occasional occurrences are normal and will not affect network performance.

Access Methods

The access method defines how signals are put on the network media.
Carrier Sense Multiple Access with Collision Detection (CSMA/CD) The access method used in Ethernet networks. In so called broadcast networks multiple nodes are attached to the same cable segment. To avoid that nodes on the network transmit traffic simultaneously and their signals collide, they listen to the network to sense if it is currently in use. If a collision does occur, it will be detected and the sender will wait for an amount of time determined by a backoff algorithm.

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) The access method used in Wireless networks for example. It is similar to CSMA/CD, but CA means that a node broadcasts a warning it is about to use the network, before it actually starts to transmit data.
Token Passing This is the access method used in Token Ring and FDDI networks. A token is passed around the network from station to station, when a station does not need to transmit data it passes the token to the next station in the logical ring. A station that receives the token and needs to transmit data seizes the token and sends a data frame, the receiving station marks the data frame as read and passes it forward along the ring to the source station. During this time no other station can transmit data which rules out collisions. The source station releases the token (passing it to the next station) when it receives the data frame and verified it was read.

NETWORK INTERFACE CARDS (NICs)

A Network Interface Card (NIC), typically an expansion card in a computer, is used to connect to the physical network media. Some mainboards and most portable computers are equipped with a built-in (onboard) NIC. NICs are available for different types of network media, the most common today being Ethernet NICs with a RJ-45 socket for UTP/STP cabling. To install a network interface card you need a free ISA or PCI expansion slot and an appropriate driver that the computer's operating system will use to communicate with the NIC. Some older ISA NICs can be manually configured to use a particular IRQ. This is done by setting jumpers or dip switches. Some other NICs allow the IRQ to be configured through the use of configuration software.

Many of today's NICs are equipped with status indicators in the form of leds. These leds can be used to troubleshoot network problems. Typically one green led indicates the NIC is physically connected to the network and flashes when activity occurs, i.e., the port is transmitting or receiving data, this is also known as a heartbeat. When the NIC supports multiple speeds, for example 10 and 100 Mbps, there can be a green led for each speed, of which one is lit indicating the current speed, possibly auto-negotiated with a hub or switch. Some NICs, as well as other network devices such as hubs, include and orange or red led which flashes when collisions occur. If the collision LED flashes repeatedly or continuously, the NIC maybe be configured incorrectly or may be malfunctioning, or there may be other devices utilizing the network heavily.

As described earlier, networks interfaces are physically configured with an address known as the MAC address (MAC is short for Media Access Layer), layer 2 address, Burned In Address (BIA), or physical address. Here's an example of a MAC address: 00-10-E3-42-A8-BC. The first 6 hexadecimal digits specify the vendor/manufacturer of the NIC, the other 6 define the host. MAC addresses are supposedly unique across the planet.

Half duplex vs. Full-duplex communication
Half-duplex means that only one host can communicate at a given time, two hosts communicating with each other will take turns transmitting. In full-duplex communication both hosts can transmit at the same time, in theory allowing twice as much data to be transmitted over the same connection.
The connections able to run at full-duplex are cross-cable connections and connections to a port on a switch, where collisions cannot occur because each end has it's own wire pair (separate segment).

MEDIA

The list below shows some important considerations to make when choosing the proper media for a particular network solution:
Cost Besides the high cost of some cable types you also have to consider that the equipment that is used to put the signal on the cable, and take it off the cable, differs a lot in price.
Maximum distance Network media is bound to a maximum cable length, because when a signal travels through the cable it will get weaker.

Flexiblity Some types of media are more flexible than others. Typically, the thinner the cable the easier it is to implement. Except for fiber optic cabling, this has to be placed with care to avoid breaks.

Susceptibility to electrical interference Some cables, such as UTP, are more susceptible to nearby high-voltage devices or other sources of electrical interference, than other cables, such as STP or fiber-optics.

Susceptibility to cross-talk Cross-talk refers to interference from other data cables.
Susceptibility to fire. Plenum cabling is designed to better withstand the introduction of fire than PVC, and, if burned, generates less smoke toxicity as a result. It is less flexible and it is more expensive. Plenum is typically used in environments such as hospitals.

RS-232

The RS-232 standard specifies serial cabling using DB-9 or DB-25 connectors. The maximum length for a RS-232 cable is 50 feet (15.25 meters) at a baudrate of 19200. The RS-232 standard is designed to supports data transfer rates up to 20 Kbps.

TWISTED PAIR

The most common type of twisted pair cabling is Unshielded Twisted Pair (UTP) cabling. This type of cabling is typically made up of 4 twisted pairs of copper wires as depicted in the image below. Each wire has its own cover, and so does the complete bundle. UTP cabling is categorized using a number. The required category depends on the network technology and the desired transmission speed. Following are the UTP categories:
Cat.1 Used for voice/telephone communication only.
Cat.2 Data rates up to 4 Mbps.
Cat.3 Data rates up to 4 Mbps in TokenRing networks, 10 Mbps in Ethernet networks, bandwidth of 16 MHz.
Cat.4 Data rates up to 16 Mbps in TokenRing networks, 10 Mbps in Ethernet networks, bandwidth of 20 MHz.
Cat.5 Data rates up to 100 Mbps, bandwidth of 100 MHz
Cat.5e Data rates up to 1 Gbps (Gigabit Ethernet), bandwidth of 100 MHz rated (tested up to 350 Mhz).
Cat.6 Data rates up to 1 Gbps (Gigabit Ethernet), bandwidth of 250 MHz rated (tested up to 550 Mhz).

10BaseT Ethernet, 100BaseTX Fast Ethernet, 1000BaseT and Token Ring are the most common networks that use twisted pair cabling and are described below.

10BaseT
The 10BaseT specification uses Cat 3, 4 and 5 UTP cabling in a star/hierarchical topology. Devices on the network are connected through a central hub.
10BaseT specifications:
- Maximum segment length is 100 meters
- Maximum data transfer speed is 10Mb/s
- Cat 3, 4 and 5 Unshielded Twisted Pair (UTP)

100BaseTX (Fast Ethernet, 802.3u)
Is similar to 10BaseT, except it requires at least Category 5 UTP or Category 1 STP cabling. Only uses 4 of the 8 wires like just like 10BaseT. The maximum data transfer rate is 100 Mb/s.

802.5 (Token Ring)
Token Ring uses the token passing method described earlier in this TechNote. While the logical topology of a Token Ring network is a ring, the physical topology is star/hierarchical as illustrated in the diagram below. Stations connect to MultiStation Access Units (look a bit like hubs) using UTP cabling which in turn are connected in a physical ring.

Token Ring specifications:
- Data transfer rate is 4 or 16 Mb/s
- Uses Twisted Pair cabling (Cat 3 for 4 MB/s, Cat 5 for 16 Mb/s)
- Logical topology ring, physical topology is star

Token Ring is originally created by IBM, and was later standardized by IEEE under the 802.5 specification. The original IBM Token Ring specification uses IBM Class 1 STP cabling with IBM proprietary connectors. This connector is called the IBM-type Data Connector (IDC) or Universal Data Connector (UDC), and is male nor female.

COAXIAL
Coaxial cabling is used primarily in 10Base2 (Thinnet) and 10Base5 (Thicknet) Ethernet networks. Coaxial cable uses a copper core with a protective shield, to reduce interference. The shield is covered with the outside cover made from PVC or plenum. The most common types are listed in the following table.
RG-58U 50 Ohm, used in 10Base2 Ethernet networks (Thinnet).
RG-8 50 Ohm, used in 10Base5 Ethernet networks (Thicknet).
RG-59 / RG-6 75 ohms, used for cable television (hence, cable modem access), video, digital audio, and telecommunication applications (for example for E1 coaxial cabling).
10Base2

10Base2 specifications:
- Maximum segment length is 185 meters
- Maximum data transfer speed is 10Mb/s
- 0.2 inch, 50 ohm RG-58 coaxial cable (Thinnet)

10Base5
Commonly referred to as Thicknet, commonly uses a bus topology. Stations are attached to the cable using MAUs, a transceiver that is attached to the cable using vampire taps that pierce the cable. A cable with AUI connectors is used to connect the transceiver to the network interface on for example a computer, hub or repeater. Both cable ends are terminated using a 50 ohm terminator.
10Base5 specifications:
- Maximum segment length is 500 meters
- Maximum data transfer speed is 10Mb/s
- 0.4 inch, 50 ohm coaxial RG-8 cabling (Thicknet)

FIBER OPTIC
Fiber optic cabling is a rather new technology that allows for fast data transfer over large distances. Fiber optic cabling is not susceptible to electrical interference, but needs expensive equipment and is fragile. There are two main types of fiber optics, the first is multi-mode, which is typically used in corporate networks' backbone. In a multi-mode cable, light travels down the fiber cable in multiple paths. Essentially, the light beam is reflected off the cladding (material surrounding the actual fiber) as it travels down the core. The other type is single-mode, this type is typically used by telephone companies to cover very large distances. In a single-mode cable, light travels thru the cable without interacting with the glass cladding (material surrounding the actual fiber), maintaining signal quality for great distances.

Fiber optic cabling is connected using SC, ST or MIC connectors.
Network technologies that use fiber optic cabling include 100BasesFX and FDDI.

100BaseFX (802.3u)
Similar to 100BaseTX but designed to operate over 2 strands of single-mode or multi-mode fiber cabling. One cable is used to send the other is used for collision detection and receiving. The maximum length of a 100BaseFX link is 400 meters in half-duplex mode, 2000 meters in full-duplex mode.

- 1000BaseLX, uses multi-mode fiber with a maximum length of 550 meters or single-mode fiber with a maximum length of 5 km
- 1000BaseSX, uses multi-mode fiber with a maximum length of 500 meters

FDDI

Another token-passing network technology is Fiber Distributed Data Interface. FDDI networks are often used as backbones for wide-area networks providing data transfer rates up to 100 Mb/s using fiber media. The use of fiber makes it immune to electrical interference, and allows it to transmit data over greater distances. FDDI provides fault tolerance by using a dual counter-rotating ring configuration, an active primary ring and a secondary ring used for backup.

WIRELESS

Infrared
Infrared (IR) communication is typically used between devices such as PDAs, laptops and printers. An advantage of IR communication is that it is not susceptible to electrical interference. The main disadvantage, besides the rather short maximum supported distance between devices, is that there must be a clear path between the devices. Supports data transfer rates up to 4 Mbps.

802.11b (Wi-fi)

The 802.11b standard specifies wireless Ethernet LAN technology. The topology used in wireless networks is known as cellular. It is a wireless structure where stations send signals to each other via wireless media hubs. The access method for 802.11b is CSMA/CA. Clients connect via wireless access points with data transfer rates up to 11 Mbps. 802.11b operates in the 2.4 GHz range. Another WLAN standard that has recently emerged, 802.11a, offers a maximum transmission speed of 54 Mbps at 5 GHz frequency.

NETWORK COMPONENTS

Repeaters Used to extend the maximum distance a cable segment can span. Repeaters grab the incoming electrical signal from the cable, amplify it, and send it out.
Hubs Hubs, also known as concentrators or multiport repeaters, are used in star/hierarchical networks to connect multiple stations/cable segments. There are two main types of hubs: passive and active. An active hub takes the incoming frames, amplifies the signal, and forwards it to all other ports, a passive hub simply splits the signal and forwards it.
Bridges Used to increase network performance by segmenting networks in separate collision domains, or increase the network size. Bridges are not aware of upper-layer protocols such as TCP/IP or IPX/SPX. They keep a table with MAC addresses of all nodes, and on which segment they are located.

Switches Similar to bridges; they also keep a table with MAC addresses per port to make switching decisions. The main difference is that a switch has more ports than a bridge, and instead of interconnecting networks it is typically used to connect hosts and servers like a hub does, but offers dedicated bandwidth per port, hence offers much higher network performance than hubs.

Routers Routers are used to interconnect multiple (sub-)networks and route information between these networks by choosing an optimal path ("route") to the destination based on addressing information from protocols such as TCP/IP or IPX/SPX. Router are also typically used to connect a LAN to a WAN or another LAN, which can use different technologies such as Token Ring, Ethernet, ISDN, Frame Relay etc.

Gateways Used to connect networks with dissimilar technologies, for example a Microsoft TCP/IP network and NetWare IPX/SPX network can be connected using a gateway. Typically implemented in software on a router.
Firewalls Protects a private network from external users, typically those from the Internet, by hiding the internal network and filtering incoming packets. A firewall is not always a hardware device, it can be implemented in software on a router or proxy server as well.

PROTOCOLS

TCP/IP

TCP/IP is today's most popular network protocol and is the protocol in the Internet. It is a routable protocol that provides connection between heterogeneous systems, these are the main reasons the protocol is so widely adapted; for example it allows communication between UNIX, Windows, Netware and Mac OS computers spread over multiple interconnected networks. The "TCP/IP protocol" is actually the "TCP/IP suite" composed of many different protocols each with its own functions. The two main protocols are in its name: the Internet Protocol and the Transmission Control Protocol.

IP addressing is assigning a 32-bit logical numeric address to a network device. Every IP address on the network must be unique. An IP address is represented in a dotted decimal format, for example: 159.101.6.8. As you can see the address is divided in 4 parts, these parts are called octets. The current used addressing schema in version 4 of IP is divided in 5 Classes:
Classes First Octet
Class A 1 126
Class B 128 191
Class C 192 223
Class D 224 239
Class E 240 254

A subnet mask is used to determine which part is the network part and which is the host part.
Default subnet masks:
Class A 255.0.0.0
Class B 255.255.0.0
Class C 255.255.255.0

IANA reserved 4 address ranges to be used in private networks, these addresses won't appear on the Internet avoiding IP address conflicts:
- 10.0.0.0 through 10.255.255.255
- 172.16.0.0 through 172.31.255.255
- 192.168.0.0 through 192.168.255.255
- 169.254.0.1 through 169.254.255.254 (reserved for Automatic Private IP Addressing)

IPX/SPX
Although current versions of Novell Netware use TCP/IP, before Netware version 5, IPX was the protocol in Netware networks. It is a small and easy to implement routable protocol developed by Novell and based on the Xerox Network System. The Netware protocol suite is a suite of several protocols for different functions, the most important being IPX and SPX. IPX is similar to the Internet Protocol from the TCP/IP suite, it is a connectionless Layer 3 (Network layer) protocol used to transfer datagrams between hosts and networks. SPX is the Transport protocol used to provide reliable transport for IPX datagrams, similar as TCP does for IP.



The frame types of two Netware hosts must match to enable communication without a router. IPX can use several frame formats, of which the two most important are listed in the following table.
Frame Format Frame Type Netware Versions
Novell 802.3 raw 802.3 Default frame type for Netware 3.11 and earlier. Supports only IPX/SPX as the upper layer protocol
IEEE 802.3 802.2 Default frame type for Netware 3.12 and 4.x. The main difference with Novell's 802.3 format is the addition of LLC field, which specifies the upper-layer protocol, such as IPX or IP.

An complete IPX network address is 80 bits in length and is represented in a hexadecimal format. As with all routable protocols it needs a network and a host portion, the network portion is 32 bits in length and is manually configured. The host portion is 48 bits in length and is derived from the MAC address of the host's network interface.

Examples of complete IPX internetwork addresses are:
- 0CC001D8.0050.BF61.6C71
- 0000ABBA.0060.9736.954B
- 00000046.0060.E92A.C2A4

NWLINK is Microsoft's implementation of IPX/SPX which allows Windows clients to communicate with Netware servers.

AppleTalk
AppleTalk was developed by Apple Computers in the early 1980s to allow file and printer sharing and mail functionality between Macintosh computers. A Mac that shares resources is called a server, and the computer connecting to it a client. Like TCP/IP, AppleTalk is not just one protocol, but a suite of several protocols for different functions. It is built-in in every Macintosh computer and requires virtually no user interaction, therefore it is very easy to administer in small network environments. Address assignment in AppleTalk networks is automatically. Besides Ethernet and TokenRing, AppleTalk can also be used on Apple's own network technology called LocalTalk, which uses UTP/STP cabling.

NetBEUI/NETBIOS

NETBios Extended User Interface is a non-routable Transport layer protocol. The reason it is non-routable is in its flat addressing schema, NETBEUI uses Netbios names to identify computers on the network that do not contain a network portion. Netbios names are sometimes referred to as friendly names. NetBIOS names are 16 characters in length and cannot contain any of the the following characters: \ / : * ? " < > | The first 15 characters represents a unique name identifying a resource, the 16th character (if you would set a name of 8 characters it is padded with spaces up to 15 characters long to allow a '16th' character) is a suffix identifying the type of resource or group of resources. For example the redirector, server, or messenger services can be installed on one computer resulting in three times the same name but with different suffixes.

NETBEUI is a broadcast protocol, meaning a computer running NETBEUI discovers the MAC address from the intended communication partner by sending out a broadcast with the NETBIOS name. The main advantage of NETBEUI is that it is small in size and easy-configurable.

Linux Installation

Linux Installation

Welcome to Red Hat Enterprise Linux

The Welcome screen does not prompt you for any input. Read over the help text in the left panel for additional instructions and information on where to register your Red Hat Enterprise Linux product.

Notice the Hide Help button at the bottom left corner of the screen. The help screen is open by default. To minimize the help text, click on Hide Help.
Click on the Next button to continue.

Language Selection

Using your mouse, select a language to use for the installation. Selecting the appropriate language also helps target your time zone configuration later in the installation. The installation program tries to define the appropriate time zone based on what you specify on this screen.

Once you select the appropriate language, click Next to continue.

Disk Partitioning Setup

Partitioning allows you to divide your hard drive into isolated sections, where each section behaves as its own hard drive. Partitioning is particularly useful if you run multiple operating systems.

On this screen, you can choose to perform automatic partitioning, or manual partitioning using Disk Druid.

Automatic partitioning allows you to perform an installation without having to partition your drive(s) yourself. If you do not feel comfortable with partitioning your system, it is recommended that you do not choose to partition manually and instead let the installation program partition for you.

To partition manually, choose the Disk Druid partitioning tool.


Partitioning Your System
If you chose to partition manually, you must tell the installation program where to install Red Hat Enterprise Linux. This is done by defining mount points for one or more disk partitions in which Red Hat Enterprise Linux is installed.

The partitioning tool used by the installation program is Disk Druid. With the exception of certain esoteric situations, Disk Druid can handle the partitioning requirements for a typical installation.

Disk Druid's Buttons

These buttons control Disk Druid's actions. They are used to change the attributes of a partition (for example the file system type and mount point) and also to create RAID devices. Buttons on this screen are also used to accept the changes you have made, or to exit Disk Druid. For further explanation, take a look at each button in order:
Edit: Used to modify attributes of the partition currently selected in the Partitions section. Selecting Edit opens a dialog box. Some or all of the fields can be edited, depending on whether the partition information has already been written to disk.
To make a RAID device, you must first create (or reuse existing) software RAID partitions. Once you have created two or more software RAID partitions, select Make RAID to join the software RAID partitions into a RAID device.

Partition Fields

Above the partition hierarchy are labels which present information about the partitions you are creating. The labels are defined as follows:

Device: This field displays the partition's device name.
Mount Point/RAID/Volume: A mount point is the location within the directory hierarchy at which a volume exists; the volume is "mounted" at this location. This field indicates where the partition is mounted. If a partition exists, but is not set, then you need to define its mount point. Double-click on the partition or click the Edit button.
Type: This field shows the partition's file system type (for example, ext2 or ext3).
Format: This field shows if the partition being created will be formatted.
Size (MB): This field shows the partition's size (in MB).
Start: This field shows the cylinder on your hard drive where the partition begins.
End: This field shows the cylinder on your hard drive where the partition ends.

Recommended Partitioning Scheme

The following is a list of recommendations for partitioning your system:
A swap partition (at least 256 MB) — swap partitions are used to support virtual memory. In other words, data is written to a swap partition when there is not enough RAM to store the data your system is processing.

If you are unsure about what size swap partition to create, make it twice the amount of RAM on your machine. It must be of type swap.
Creation of the proper amount of swap space varies depending on a number of factors including the following (in descending order of importance):
The applications running on the machine.
The amount of physical RAM installed on the machine.
The version of the OS.
Swap should equal 2x physical RAM for up to 2 GB of physical RAM, and then 1x physical RAM for any amount above 2 GB, but never less than 32 MB.
Using this formula, a system with 2 GB of physical RAM would have 4 GB of swap, while one with 3 GB of physical RAM would have 5 GB of swap. Creating a large swap space partition can be especially helpful if you plan to upgrade your RAM at a later time.
For systems with really large amounts of RAM (more than 32 GB) you can likely get away with a smaller swap partition (around 1x, or less, of physical RAM).
A root partition (500 MB - 5.0 GB) — this is where "/" (the root directory) is located. In this setup, all files — except for files stored in /boot (on x86, AMD64, and Intel EM64T) are on the root partition.
A 500 MB partition allows you to install a minimal installation; while a 5.0 GB root partition lets you perform a full installation, choosing all package groups.
It is recommended that you create a /boot/ partition (100 MB). /boot/ contains the kernels, along with files used during the bootstrap process

Network Configuration

If you do not have a network device, this screen does not appear during your installation and you should advance to The installation program automatically detects any network devices you have and displays them in the Network Devices list.

Once you have selected a network device, click Edit. From the Edit Interface pop-up screen, you can choose to configure the IP address and Netmask of the device via DHCP (or manually if DHCP is not selected) and you can choose to activate the device at boot time. If you select Activate on boot, your network interface is started when you boot. If you do not have DHCP client access or you are unsure what to provide here, please contact your network administrator.

Firewall Configuration

Red Hat Enterprise Linux offers firewall protection for enhanced system security. A firewall exists between your computer and the network, and determines which resources on your computer remote users on the network can access. A properly configured firewall can greatly increase the security of your system.

Firewall Configuration

Next, you can decide whether to enable a firewall for your Red Hat Enterprise Linux system.
No firewall
No firewall provides complete access to your system and does no security checking. Security checking is the disabling of access to certain services. This should only be selected if you are running on a trusted network (not the Internet) or plan to do more firewall configuration later.

Enable firewall

If you choose Enable firewall, connections are not accepted by your systems (other than the default settings) that are not explicitly defined by you. By default, only connections in response to outbound requests, such as DNS replies or DHCP requests are allowed. If access to services running on this machine is needed, you can choose to allow specific services through the firewall.

If you are connecting your system to the Internet, this is the safest option to choose.
Next, select which services, if any, should be allowed to pass through the firewall.
Enabling these options allow the specified services to pass through the firewall. Note, these services may not be installed on the system by default. Make sure you choose to enable any options that you may need.

Remote Login (SSH)

Secure Shell (SSH) is a suite of tools for logging in to and executing commands on a remote machine. If you plan to use SSH tools to access your machine through a firewall, enable this option. You need to have the openssh-server package installed in order to access your machine remotely, using SSH tools.

Web Server (HTTP, HTTPS)

The HTTP and HTTPS protocols are used by Apache (and by other Web servers) to serve webpages. If you plan on making your Web server publicly available, enable this option. This option is not required for viewing pages locally or for developing webpages. You must install the httpd package if you want to serve webpages.

File Transfer (FTP)

The FTP protocol is used to transfer files between machines on a network. If you plan on making your FTP server publicly available, enable this option. You must install the vsftpd package in order to publicly serve files.

Mail Server (SMTP)

If you want to allow incoming mail delivery through your firewall, so that remote hosts can connect directly to your machine to deliver mail, enable this option. You do not need to enable this if you collect your mail from your Internet Service Provider's server using POP3 or IMAP, or if you use a tool such as fetchmail. Note that an improperly configured SMTP server can allow remote machines to use your server to send spam.

Language Support Selection

You can install and support multiple languages for use on your system.
You must select a language to use as the default language. The default language is the language used on the system once the installation is complete. Typically, the default language is the language you selected to use during the installation. If you choose to install other languages during this installation, you can change your default language after the installation. If you are only going to use one language on your system, selecting only that language saves significant disk space.

Caution

If you select only one language, you can only use that specified language after the installation is complete.

Language Support Selection

To use more than one language on your system, choose specific languages to be installed or select all languages to have all available languages installed on your Red Hat Enterprise Linux system.

Use the Reset button to cancel your selections. Resetting reverts to the default; only the language you selected for use during the installation is installed. Tip To change the language configuration after you have completed the installation, use the Language Configuration Tool.

Type the system-config-language command in a shell prompt to launch the Language Configuration Tool. If you are not root, it prompts you for the root password to continue.
Time Zone Configuration

Set your time zone by selecting the city closest to your computer's physical location.

There are two ways for you to select your time zone:

Using your mouse, click on the interactive map to select a specific city (represented by a yellow dot). A red X appears indicating your selection.

You can also scroll through the list at the bottom of the screen to select your time zone. Using your mouse, click on a location to highlight your selection.

Configuring the Time Zone

Select System Clock uses UTC if you know that your system is set to UTC.
To change your time zone configuration after you have completed the installation, use the Time and Date Properties Tool.

Type the system-config-date command in a shell prompt to launch the Time and Date Properties Tool. If you are not root, it prompts you for the root password to continue.
To run the Time and Date Properties Tool as a text-based application, use the command timeconfig.

Set Root Password

Setting up a root account and password is one of the most important steps during your installation. Your root account is similar to the administrator account used on Windows NT machines. The root account is used to install packages, upgrade RPMs, and perform most system maintenance. Logging in as root gives you complete control over your system. Note
The root user (also known as the superuser) has complete access to the entire system; for this reason, logging in as the root user is best done only to perform system maintenance or administration.

Root Password

Use the root account only for system administration. Create a non-root account for your general use and su - to root when you need to fix something quickly. These basic rules minimize the chances of a typo or an incorrect command doing damage to your system.
To become root, type su - at the shell prompt in a terminal window and then press Enter. Then, enter the root password and press Enter.

The installation program prompts you to set a root password for your system. You cannot proceed to the next stage of the installation process without entering a root password
The root password must be at least six characters long; the password you type is not echoed to the screen. You must enter the password twice; if the two passwords do not match, the installation program asks you to enter them again.

Tip

To change your root password after you have completed the installation, use the Root Password Tool.

Type the system-config-rootpassword command in a shell prompt to launch the Root Password Tool. If you are not root, it prompts you for the root password to continue.
A root password is the administrative password for your Red Hat Enterprise Linux system. You should only log in as root when needed for system maintenance. The root account does not operate within the restrictions placed on normal user accounts, so changes made as root can have implications for your entire system.

Package Group Selection

Now that you have made most of the choices for your installation, you are ready to confirm the default package selection or customize packages for your system.

The Package Installation Defaults screen appears and details the default package set for your Red Hat Enterprise Linux installation. This screen varies depending on the version of Red Hat Enterprise Linux you are installing.

To customize your package set further, select Customize the set of packages to be installed option on the screen. Clicking Next takes you to the Package Group Selection screen.
You can select package groups, which group components together according to function (for example, X Window System and Editors), individual packages, or a combination of the two.
To select a component, click on the checkbox beside it.

Package Group Selection

Select each component you wish to install. Selecting Everything (at the end of the component list) installs all packages included with Red Hat Enterprise Linux.
Once a package group has been selected, click on Details to view which packages are installed by default, and to add or remove optional packages from that group. (Package Group Details)

Preparing to Install

A screen preparing you for the installation of Red Hat Enterprise Linux now appears.
For your reference, a complete log of your installation can be found in /root/install.log once you reboot your system.

Warning

If, for some reason, you would rather not continue with the installation process, this is your last opportunity to safely cancel the process and reboot your machine. Once you press the Next button, partitions are written and packages are installed. If you wish to abort the installation, you should reboot now before any existing information on any hard drive is rewritten.

Installing Packages

At this point there is nothing left for you to do until all the packages have been installed. How quickly this happens depends on the number of packages you have selected and your computer's speed.

Installation Complete

Congratulations! Your Red Hat Enterprise Linux installation is now complete!
The installation program prompts you to prepare your system for reboot.
DOS versus Linux commands

In this appendix, we matched DOS commands with their Linux equivalent.
As an extra means of orientation for new users with a Windows background, the table below lists MS-DOS commands with their Linux counterparts. Keep in mind that Linux commands usually have a number of options. Read the Info or man pages on the command to find out more.

Overview of DOS/Linux commands

DOS commands	Linux command
/?	man or command --help
cd	cd
chdir	pwd
cls	clear
copy	cp
date	date
del	rm
dir	ls
echo	echo
edit	vim (or other editor)
exit	exit
fc	diff
find	grep
format	mke2fs or mformat
mem	free
mkdir	mkdir
more	more or even less
move	mv
ren	mv
time	date