DNS :
 
(Domain Name Server) – Used to map names to IP addresses and vice versa. Domain Name Servers maintain central lists of domain name/IP addresses and map the domain names in your Internet requests to other servers on the Internet until the specified web site is found.
 
Domain :  A group of computers and devices on a network that are administered as a unit with common rules and procedures. Within the Internet, domains are defined by the IP address. All devices sharing a common part of the IP address are said to be in the same domain.
 
IP address :  Every computer connected to the Internet is assigned a unique number known as an Internet Protocol (IP) address. Since these numbers are usually assigned in country-based blocks, an IP address can often be used to identify the country from which a computer is connecting to the Internet.
 
MASK :  A bit mask used to identify which bits in an address (usually an IP address) are network significant, subnet significant, and host significant portions of the complete address. This mask is also known as the subnet mask because the subnetwork portion of the address can be determined by comparing the binary version of the mask to an IP address in that subnet. The mask holds the same number of bits as the protocol address it references.
 
Gateway address : The address of the gateway used to reach a specified destination; for example, on a network or the Internet. Gateways are devices that route packets between the different physical networks.
 
MAC address :  In computer networking, the Media Access Control (MAC) address is every bit as important as an IP address. Learn in this article how MAC addresses work and how to find the MAC addresses being used by a computer.

What Is a MAC Address?
The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.

MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:
MM:MM:MM:SS:SS:SS

MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,

00:A0:C9:14:C8:29

The prefix
00A0C9
indicates the manufacturer is Intel Corporation.

Why MAC Addresses?
Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.
MAC vs. IP Addressing
Whereas MAC addressing works at the data link layer, IP addressing functions at the network layer (layer 3). It's a slight oversimplification, but one can think of IP addressing as supporting the software implementation and MAC addresses as supporting the hardware implementation of the network stack. The MAC address generally remains fixed and follows the network device, but the IP address changes as the network device moves from one network to another.

IP networks maintain a mapping between the IP address of a device and its MAC address. This mapping is known as the ARP cache or ARP table. ARP, the Address Resolution Protocol, supports the logic for obtaining this mapping and keeping the cache up to date.

DHCP also usually relies on MAC addresses to manage the unique assignment of IP addresses to devices.


 

DHCP :  (Dynamic Host Configuration Protocol) This is a protocol that lets network administrators centrally manage and automate the assignment of IP Addresses on the corporate network. When a company sets up its computer users with a connection to the Internet , an IP address must be assigned to each machine. Without DHCP , the IP address must be entered manually at each computer . DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.DHCP uses the concept of a ‘lease’ or amount of time that a given IP address will be valid for a computer. Using very short leases, DHCP can dynamically reconfigure networks in which there are more computers than there are available IP addresses.
 
USB & Firewire USB and FireWire (IEEE 1394a nd b) represent the newer generations of external serial interfaces being adopted to reduce PC and connection costs and to improve performance.
USB (1.x and 2.0)
 
 
The USB specification
defines A and B type connectors. A type connects
to the host or a hub. Type B connects to the end
peripheral.

A new 'On-the-Go (OTG)' specification introduces a
smaller (really) connector
and peer-to-peer operation.

Great to see that the USB
folk make their specs freely available unlike the
IEEE 1394 folks. .

Type A Pin assignment
Pin . Name Color          Notes.
1 VBUS      Red Power
2 D- White Data -
3 D+ Green Data +
4 GND Black Ground
Type B Pin assignment
Pin  .Name       Color       Notes
1 VBUS Red Power
2 D- White Data -
3 D+ Green Data +
4 GND Black Ground
Mini-USB Type A/B Pin assignment

Defined as part of the 'On-the-Go (OTG)' enhancement, features a single connector type (A/B) and peer-to-peer operation.
 
Pin Name Color Notes
1 VBUS Red Power
2 D- White Data -
3 D+ Green Data +
4 ID - Type A - GND: Type B - NC
5 GND Black Ground
   
IEEE 1394 (Firewire a.k.a. i.Link)

The IEEE high speed serial connector is known as Firewire and i.Link (Japan). The IEEE 1394a-1995 specification provides up to 400 M bit/sec and uses either a 6 pin connector (PCs/Computers) or a 4 pin connector (camcorders and AV equipment). The latest specification IEEE 1394b provides up to 800 M bit/sec (but is slated for 3.2 G bit/s) and uses a 9 pin connector which may operate in 'biligual mode' (will connect to either a 4 or 6 pin IEEE 1394a connectors - needs a special converter cable) or 'beta mode' (will connect to another IEEE 1394b system).

Firewire uses the Open Host Controller Interface (OHCI)

As always the lack of freely available specifications is just a pain - leading to confusion and plain stupidity. It is a shame that IEEE 1394 working group could not take a leaf out of the same IEEE 802 group which now provides specs at no cost 6 months after their initial publication. Sigh.
 
   
 
Firewire/i.Link 6 Pin
Connector Assignment

This connector is usually
found on PCs (Apple
especially) and disk systems.
 
.
Firewire/i.Link 4 Pin
Connector Assignment

This very compact connector
is usually found on camcorders
and other digital AV equipment.
 
   
Firewire/i.Link 9 Pin
Connector Assignment

This is the new IEEE 1394b
(Firewire 800) connector which
allows interconnection to older
1394a systems in 'bilingual
mode'(4 or 6 pin - using an
appropriate converter cable).
In 'beta mode' allows connection
to other 1394b systems.
  Pin Name Color Notes
1 Power - Power (18V - 25V, 15W)
2 GND - Ground
3 TPB- - Pair B -
4 TPB+ - Pair B +
5 TPA- - Pair A -
6 TPA+ - Pair A +


Pin Name Color Notes
1 TPB- - Pair B -
2 TPB+ - Pair B +
3 TPA- - Pair A -
4 TPA+ - Pair A +


Pin Name Color Notes
1 TPB- - Pair B -
2 TPB+ - Pair B +
3 TPA- - Pair A -
4 TPA+ - Pair A +
5 TPA(R) - Pair A Ground Ref.
6 VG - Power Ground
7 SC -
Status Contact (Reserved NC)
8 VP -
Power (18-25V DC, 15W)
9 TPB(R) -