D-Link DES-3226L Technical Information download pdf (Page 125)

Glossary 125

Internet Protocol. The method or protocol by which data

is sent from one computer to another on the Internet. Each

computer (known as a host) on the Internet has at least one

IP address that uniquely identifies it among all other

computers on the Internet. When you send or receive data

(for example, an e-mail note or a Web page), the message

gets divided into little chunks called packets. Each of these

packets contains both the sender's Internet address and the

receiver's address. Any packet is sent first to a gateway

computer that understands a small part of the Internet. The

gateway computer reads the destination address and

forwards the packet to an adjacent gateway that in turn

reads the destination address and so forth across the

Internet until one gateway recognizes the packet as

belonging to a computer within its immediate

neighborhood or domain. That gateway then forwards the

packet directly to the computer whose address is specified.

Because a message is divided into a number of packets,

each packet can, if necessary, be sent by a different route

across the Internet. Packets can arrive in a different order

than they were sent. The Internet Protocol just delivers

them. It's up to another protocol, the Transmission Control

Protocol (TCP) to put them back in the right order. IP is a

connectionless protocol, which means that there is no

continuing connection between the end points that are

communicating. Each packet that travels through the

Internet is treated as an independent unit of data without

any relation to any other unit of data. (The reason the

packets do get put in the right order is because of TCP, the

connection-oriented protocol that keeps track of the packet

sequence in a message.) In the Open Systems

Interconnection (OSI) communication model, IP is in

Layer 3, the Networking Layer. The most widely used

version of IP today is IP version 4 (IPv4). However, IP

version 6 (IPv6) is also beginning to be supported. IPv6

provides for much longer addresses and therefore for the

possibility of many more Internet users. IPv6 includes the

capabilities of IPv4 and any server that can support IPv6

packets can also support IPv4 packets.

IVL. Independent VLAN Learning (IVL) allows unicast

address-to-port mappings to be created based on a MAC

Address in conjunction with a VLAN ID.

LAN. See “Local Area Network” on page 125.

Learning. The bridge examines the Layer 2 source

addresses of every frame on the attached networks (called

listening) and then maintains a table, or cache, of which

MAC addresses are attached to each of its ports.

Local Area Network. A group of computers that are

located in one area and are connected by less than 1,000

feet of cable. A typical LAN might interconnect

computers and peripherals on a single floor or in a single

building. LANs can be connected together, but if modems

and telephones connect two or more LANs, the larger

network constitutes what is called a WAN or Wide Area

Network.

MAC. (1) Medium Access Control. In LANs, the

sublayer of the data link control layer that supports

medium-dependent functions and uses the services of the

physical layer to provide services to the logical link

control (LLC) sublayer. The MAC sublayer includes the

method of determining when a device has access to the

transmission medium. (2) Message Authentication Code.

In computer security, a value that is a part of a message or

accompanies a message and is used to determine that the

contents, origin, author, or other attributes of all or part of

the message are as they appear to be. (IBM Glossary of

Computing Terms)

Management Information Base. When SNMP devices

send SNMP messages to the management console (the

device managing SNMP messages), it stores information

in the MIB.

MDC. Management Data Clock.

MDI. Management Data Interface.

MDIO. Management Data Input/Output.

MDIX. Management Dependent Interface Crossover.

MIB. See “Management Information Base” on page 125.

Multicasting. To transmit a message to specific

recipients across a network. A simple example of

multicasting is sending an e-mail message to a mailing list.

Teleconferencing and videoconferencing also use

multicasting, but require more robust protocols and

networks. Standards are being developed to support

multicasting over a TCP/IP network such as the Internet.

These standards, IP Multicast and Mbone, will allow users

to easily join multicast groups. Note that multicasting

refers to sending a message to a select group whereas

broadcasting refers to sending a message to everyone

connected to a network. The terms multicast and

narrowcast are often used interchangeably, although

narrowcast usually refers to the business model whereas

multicast refers to the actual technology used to transmit

the data.

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