The 3 Types of VPN(Virtual Private Layer)

1.) INTRANET VPN - If a company has one or more remote locations that they wish to join in a single private network, they can create an intranet VPN to connect LAN to LAN.

2.) EXTRANET VPN - When a company has a close relationship with another company (for example, a partner, supplier or customer), they can build an extranet VPN that connects LAN to LAN, and that allows all of the various companies to work in a shared environment.

3.) Remote-Access VPN - also called a virtual private dial-up network (VPDN), is a user-to-LAN connection used by a company that has employees who need to connect to the private network from various remote locations.

Data Center Technology - Technology infrastructures are a costly investment and require constant vigilance to protect and maintain. As networks increase in size, reach, and sophistication, so does their cost.



(WAN) Wide Area Networks












VIRTUAL PRIVATE NETWORKS















STORAGE - Area Networks

METROPOLITAN - Area Networks














BROADCAST DOMAIN















(LAN) Local - Area Networks

OPEN SYSTEM INTERCONNECTION LAYER AND FUNCTIONS

APPLICATION LAYER - is the seventh level of the seven-layer OSI model, and the top layer of the TCP/IP model. It interfaces directly to and performs common application services for the application processes; it also issues requests to the Presentation Layer (OSI).

PRESENTATION LAYER - is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems.

SESSION LAYER - provides the mechanism for opening, closing and managing a session between end-user application processes, i.e. a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session Layers are commonly used in application environments that make use of remote procedure calls (RPCs).

TRASPORT LAYER - is a group of methods and protocols within a layered architecture of network components, within which it is responsible for encapsulating application data blocks into datagrams (packets) suitable for transfer to the network infrastructure for transmission to the destination host, or managing the reverse transaction by abstracting network datagrams and delivering them to an application.

NETWORK LAYER - is responsible for end-to-end (source to destination) packet delivery including any routing through intermediate hosts, whereas the link layer is responsible for node-to-node (hop-to-hop) frame delivery on the same link.

DATA - LINK LAYER - is the layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment. The Data Link Layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the Physical layer.

PHYSICAL LAYER - is a fundamental layer upon which all higher level functions in a network are based. However, due to the plethora of available hardware technologies with widely varying characteristics, this is perhaps the most complex layer in the OSI architecture.

NETWORKING I

COLLISION - is an isolated event in which two or more bodies (colliding bodies) exert relatively strong forces on each other for a relatively short time.


TYPES OF COLLISIONS

1. LOCAL COLLISION - in CSMA/CD computer networks, is a collision that occurs at the NIC as opposed to on the wire. On UTP cable a local collision is detected on the local segment only when a station detects a signal on the RX pair at the same time it is sending on the TX pair.

2. REMOTE COLLISION - in CSMA/CD computer networks, is a collision that occurs when a frame having length less than minimum length and with an incorrect FCS (Frame Check Sequence), is transmitted. This frame causes a collision at the remote end which will not be detected by the transmitter.

3. LATE COLLISION - is a type of collision found in the CSMA/CD protocol standard. If a collision error occurs after the first 512 bit times of data are transmitted by the transmitting station, a late collision is said to have occurred. Importantly, late collisions are not re-sent by the NIC unlike collisions occurring before the first 64 octets; it is left for the upper layers of the protocol stack to determine that there was loss of data.

JABBER - is an initiative to produce an open source, XML-based instant messaging platform. Similar to the Linux and Apache projects, Jabber developers volunteer their time to work with the code over the Internet.

COLLISION DOMAIN - is a physical network segment where data packets can "collide" with one another for being sent on a shared medium, in particular in the Ethernet networking protocol. This is an Ethernet term used to describe a network scenario wherein one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it.

MULTIMODE FIBER (multimode fiber or MM fiber or fibre) - is a type of optical fiber mostly used for communication over shorter distances, such as within a building or on a campus. Typical multimode links have data rates of 10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters—more than sufficient for the majority of premises applications.

SINGLE-MODE FIBER (SMF) - is an optical fiber designed to carry only a single ray of light (mode). This ray of light often contains a variety of different wavelengths. Although the ray travels parallel to the length of the fiber, it is often called the transverse mode since its electromagnetic vibrations occur perpendicular (transverse) to the length of the fiber. Single-mode optical fibers are also called monomode optical fibers, single-mode optical waveguides, or unimode fibers.


PICTURE FOR LOOSE - TUBE FIBER














PICTURE FOR TIGHT - BUFERRED FIBER

PART I

Bit - A bit (short for binary digit) is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1. Although computers usually provide instructions that can test and manipulate bits, they generally are designed to store data and execute instructions in bit multiples called bytes. In most computer systems, there are eight bits in a byte.

Byte - is a unit of data that is eight binary digits long. A byte is the unit most computers use to represent a character such as a letter, number, or typographic symbol (for example, "g", "5", or "?"). A byte can also hold a string of bits that need to be used in some larger unit for application purposes (for example, the stream of bits that constitute a visual image for a program that displays images or the string of bits that constitutes the machine code of a computer program).

Kb (kilobit) - is a unit of information, abbreviated kbit (or kb).The standard definition is 1 kilobit = 103 bit = 1,000 bit. In the context of storage-memory and address-space sizes, the alternative binary definition of 210 = 1,024 bit is occasionally used (see Binary prefix), although this usage is ambiguous.

KB (kilobyte) - As a measure of computer memory or storage, a kilobyte (KB or Kbyte*) is approximately a thousand bytes (actually, 2 to the 10th power, or decimal 1,024 bytes).

Mb (megabit) - In data communications, a megabit is a million binary pulses, or 1,000,000 (that is, 106) pulses (or "bits"). It's commonly used for measuring the amount of data that is transferred in a second between two telecommunication points. For example, a U.S. phone company T-carrier system line is said to sustain a data rate of 1.544 megabits per second. Megabits per second is usually shortened to Mbps.

MB (megabyte) - is a unit of measurement used to quantify computer memory and storage. One megabyte is the equivalent of approximately one million bytes and one thousand kilobytes (the exact conversion is 1 megabyte=1,048,576 bytes and 1,024 kilobytes in binary measurement).

GB (gigabyte) - Is composed of One billion bytes.

TB (terabyte) - Is a measure of computer storage capacity and is 2 to the 40th power or approximately a thousand billion bytes (that is, a thousand gigabytes).

kbps (kilobits per second) - A measure of data transfer. A 56Kbps dial-up modem transfers data at about 7.2 kilobytes (KB) per second.

kBps (kilobytes per second) - Another unit of data transmission is the kilobyte per second (kBps or kbyte/s) and is one-eighth that of a kilobit per second.

Mbps (megabits per second) - Because there are 8 bits in a byte, a transfer speed of 8 megabits per second (8 Mbit/s) is equivalent to 1000000 bytes per second (approximately 977 KiB/s).

MBps (megabytes per second) - Is a unit of data transfer rate that is sometimes used when describing the flow of data to and from a computer storage device.

Gbps (gigabits per second) - Stands for billions of bits per second and is a measure of bandwidth on a digital data transmission medium such as optical fiber. With slower media and protocols, bandwidth may be in the Mbps (millions of bits or megabits per second) or the Kbps (thousands of bits or kilobits per second) range.

Tbps (terabits per second) - In measuring data transmission speed, a terabit is one trillion bits, or 1,000,000,000,000 (that is, 1012) bits. A terabit is used for measuring the amount of data that is transferred in a second between two telecommunication points or within network devices. For example, several companies are building a network switch that passes incoming packets through the device and out again at a terabits-per-second speed.

Hz (hertz) - The hertz (symbol: Hz) is a measure of frequency, informally defined as the number of events occurring per second. It is the basic unit of frequency in the International System of Units (SI), and is used worldwide in both general-purpose and scientific contexts.

MHz (megahertz) - One megahertz is equal to one million cycles per second. It is used to measure transmission speeds of electronic devices. The most common area you will see Megahertz used is in measuring processor clock speed, such as an 800 Mhz Pentium III.

GHz (gigahertz) - One gigahertz is equal to 1,000 megahertz (MHz) or 1,000,000,000 Hz. It is commonly used to measure computer processing speeds. For many years, computer CPU speeds were measured in megahertz, but after personal computers eclipsed the 1,000 Mhz mark around the year 2000, gigahertz became the standard measurement unit. After all, it is easier to say "2.4 Gigahertz" than "2,400 Megahertz."

PART II

Unit...............................Bytes...................................Bits

Bit(b).............................0.125 byte..............................1 bit
Byte (B)........................1 byte......................................8 bits
Kilobyte (KB)................1,024 byte...................................8,192 bits
Megabyte (MB)............1,048,576 byte...........................8,388,608 bits
Gigabyte (GB)..............1,073,741,824 byte.....................67,108,864 bits
Terabyte (TB)............1,099,511,627,776 byte..............8,796,093,022,208

PART III

1. The connection to the Internet can be broken down into which of the following?
Ans: B. Logical connection

2. What is the main circuit board of a computer?
Ans: B. Motherboard

3. What are PCMCIA slots?
Ans: C. Expansion slots for a NIC

4. What is a NIC?
Ans: B. A printed circuit board that provides network communication.

5. Which of the following is/are the resource(s) you need before you intall a NIC?
Ans: D. All of the above

6. Which number system is based on powers of 2?
Ans: D. ASCII

7. The smallest unit of data in a computer?
Ans: C. kpbs

8. A standard measurement of the rate at which data is transferred over a network connection?Ans: D. MHz

9. A unit of frequency; the rate of change in the state or cycle in a sound wave, alternating current, or another cylical waveform?
Ans: C. kbps

10. A unit of measurement that describes the size of a data file, the amount of space on a disk or another storage medium, or the amount of data being tranferred over a network?
Ans: B. Byte