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Packet: when the information sends by the network, it’s
divided in blocks (at the network level). Each block is called
packet.

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Router:
device that provides connectivity at the network
level of the OSI model.
Its main function is to send or route packets of data from one
network to another, (to
interconnect subnets),
meaning a subset of IP machines that can communicate without the
intervention of a router (through network bridges or a switch).

IP: Internet Protocol. It’s used in the network layer, and
the main function is the bidirectional use in
origin or destination of communication to transmit data through a
non-connection oriented protocol that transfers packets switched
through different physical networks previously linked according to
the OSI standard of data link.

TCP: Transmission Control Protocol. It’s
one of the main protocols of the transport layer of the TCP / IP
model. Works at the application level.
When the data is provided to the IP protocol, it groups them into IP
datagrams. It’s oriented
to connection.

UDP: User Data Protocol. It’s a transport level protocol,
that allows sending datagrams through the network
without having previously established a connection, since the
datagram itself incorporates sufficient addressing information in
its header. It’s not oriented to
connection.

NAT: Network Address Translation. It’s a
mechanism used by IP routers to exchange packets between two
networks that mutually assign incompatible addresses. It consists of
converting, in real time, the addresses used in the transported
packages. It is also necessary to edit the packets to allow the
operation of protocols that include address information within the
protocol conversation. Currently it is the solution used to supply
the lack of IPv4 addresses.

ICMP:
Internet Control Message Protocol. Is a protocol that control and
notification errors of the IP. It’s used to indicate, for example,
to send error messages when a router (or host) can’t be located.

Subnet mask: combination of bits (IPv4: 8 bits, IPV6: 64
bits) used to delimit the scope of a computer
network. The functions is
to indicate to the devices which part of the IP address is the
network number (including
the subnet), and
which part corresponds to the host.

TTL: Time-To-Live. Indicate (with an integer) how many nodes
can pass a packet before being discarted. It
prevents a package from traveling infinitely without reaching its
destination. This value is initialized in
the transmitter and has the function of discounting a unit according
to the IP datagram from one counter to another, so it must be
recalculated in each hop.

PPP:
Point-to-Point Protocol. This protocol works in the data link layer,
and it’s used to establish a direct connection between tho network
nodes (for example two routers). Can provide services as
authentication, encryption and compression.

Host:
computer (or other devices) connected to a network that provide and
use services from its own.

Physical
layer: the lowest layer in OSI model. Works this the physical
medium (electronic circuit transmission).

Data link
layer: the second layer in OSI model. Transfers data frames
between the connected nodes as WAN, LAN, …

Network layer: the third layer in the OSI model. Works
choosing about the best path may use the physical layer (identify
the existing routing between one or more networks).

Transport layer: the fourth layer in the OSI model. This
layer transmit the data without errors between sender and receptor.
Basically, this layer provide a reliable and
economical data transport from the source machine to the destination
machine.

Session
layer: the fifth layer in the OSI model. Is the responsible for
transportins the data (in packages) to the destination machine.
Provide independency of the physical medium. There are two different
protocols in this layer: UDP and TCP.

Presentacion layer: the sixth layer in the OSI model. This
layer provide communication between network devices. The
objective is to take charge of the representation of the
information, so that although different equipment may have different
internal representations of characters, the data arrive in a
recognizable manner.

Application layer: the seventh layer (the
highest) in the OSI model. Offers
the possibility of access to the other layers services. Defines too
the protocols that the applications can use to exchange data.

WAN:
Wide Area Network. Is a network that connect several LAN’s,
independiently of its physical location. Can be built by the
Internet Service Providers or private companies.

LAN:
Local Area Network. Is a network that connect several computers in
the same physical location (office, house, …).