Download Proxy server

A gateway is a network point that acts as an entrance to another network. On the Internet, a node
or stopping point can be either a gateway node or a host (end-point) node. Both the computers of
Internet users and the computers that serve pages to users are host nodes. The computers that
control traffic within your company's network or at your local Internet service provider (ISP) are
gateway nodes.
In the network for an enterprise, a computer server acting as a gateway node is often also acting as
a proxy server and a firewall server. A gateway is often associated with both a router, which knows
where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the
actual
path
in
and
out
of
the
gateway
for
a
given
packet.
Network:
In information technology, a network is a series of points or nodes interconnected by
communication paths. Networks can interconnect with other networks and contain subnetworks.
The most common topology or general configurations of networks include the bus, star, and Token
Ring topologies. Networks can also be characterized in terms of spatial distance as local area
networks (LAN), metropolitan area networks (MAN), and wide area networks (WAN).
A given network can also be characterized by the type of data transmission technology in use on it
(for example, a TCP/IP or Systems Network Architecture network); by whether it carries voice, data,
or both kinds of signals; by who can use the network (public or private); by the usual nature of its
connections (dial-up or switched, dedicated or nonswitched, or virtual connections); and by the
types of physical links (for example, optical fiber, coaxial cable, and Unshielded Twisted Pair).
Large telephone networks and networks using their infrastructure (such as the Internet) have
sharing and exchange arrangements with other companies so that larger networks are created.
Nodo:
In a network, a node is a connection point, either a redistribution point or an end
point for data transmissions. In general, a node has programmed or engineered
capability to recognize and process or forward transmissions to other nodes.
host
The term "host" is used in several contexts, in each of which it has a slightly
different meaning:
1) In Internet protocol specifications, the term "host" means any computer that has full two-way
access to other computers on the Internet. A host has a specific "local or host number" that,
together with the network number, forms its unique IP address. If you use Point-to-Point Protocol
to get access to your access provider, you have a unique IP address for the duration of any
connection you make to the Internet and your computer is a host for that period. In this context, a
"host" is a node in a network.
2) For companies or individuals with a Web site, a host is a computer with a Web server that
serves the pages for one or more Web sites. A host can also be the company that provides that
service, which is known as hosting.
3) In IBM and perhaps other mainframe computer environments, a host is a mainframe computer
(which is now usually referred to as a "large server"). In this context, the mainframe has intelligent
or "dumb" workstations attached to it that use it as a host provider of services. (This does not mean
that the host only has "servers" and the workstations only have "clients." The server/client
relationship is a programming model independent of this contextual usage of "host.")
4) In other contexts, the term generally means a device or program that provides services to some
smaller
or
less
capable
device
or
program.
ISP
An ISP (Internet service provider) is a company that provides individuals and other companies
access to the Internet and other related services such as Web site building and virtual hosting. An
ISP has the equipment and the telecommunication line access required to have a point-of-presence
on the Internet for the geographic area served. The larger ISPs have their own high-speed leased
lines so that they are less dependent on the telecommunication providers and can provide better
service to their customers. Among the largest national and regional ISPs are AT&T WorldNet, IBM
Global Network, MCI, Netcom, UUNet, and PSINet.
ISPs also include regional providers such as New England's NEARNet and the San Francisco Bay
area BARNet. They also include thousands of local providers. In addition, Internet users can also
get access through online service providers (OSP) such as America Online and Compuserve.
The larger ISPs interconnect with each other through MAE (ISP switching centers run by MCI
WorldCom) or similar centers. The arrangements they make to exchange traffic are known as
peering agreements. There are several very comprehensive lists of ISPs world-wide available on
the Web.
An ISP is also sometimes referred to as an IAP (Internet access provider). ISP is sometimes used
as an abbreviation for independent service provider to distinguish a service provider that is an
independent,
separate
company
from
a
telephone
company.
Server
1) In general, a server is a computer program that provides services to other
computer programs in the same or other computers.
2) The computer that a server program runs in is also frequently referred to as a server (though it
may contain a number of server and client programs).
3) In the client/server programming model, a server is a program that awaits and fulfills requests
from client programs in the same or other computers. A given application in a computer may
function as a client with requests for services from other programs and also as a server of requests
from other programs.
Specific to the Web, a Web server is the computer program (housed in a computer) that serves
requested HTML pages or files. A Web client is the requesting program associated with the user.
The Web browser in your computer is a client that requests HTML files from Web servers.
Proxy server
In an enterprise that uses the Internet, a proxy server is a server that acts as an intermediary
between a workstation user and the Internet so that the enterprise can ensure security,
administrative control, and caching service. A proxy server is associated with or part of a gateway
server that separates the enterprise network from the outside network and a firewall server that
protects the enterprise network from outside intrusion.
A proxy server receives a request for an Internet service (such as a Web page request) from a user.
If it passes filtering requirements, the proxy server, assuming it is also a cache server, looks in its
local cache of previously downloaded Web pages. If it finds the page, it returns it to the user
without needing to forward the request to the Internet. If the page is not in the cache, the proxy
server, acting as a client on behalf of the user, uses one of its own IP addresses to request the
page from the server out on the Internet. When the page is returned, the proxy server relates it to
the original request and forwards it on to the user.
To the user, the proxy server is invisible; all Internet requests and returned responses appear to be
directly with the addressed Internet server. (The proxy is not quite invisible; its IP address has to be
specified as a configuration option to the browser or other protocol program.)
An advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are
frequently requested, these are likely to be in the proxy's cache, which will improve user response
time. In fact, there are special servers called cache servers. A proxy can also do logging.
The functions of proxy, firewall, and caching can be in separate server programs or combined in a
single package. Different server programs can be in different computers. For example, a proxy
server may in the same machine with a firewall server or it may be on a separate server and
forward
requests
through
the
firewall.
firewall
The term you selected is being presented by searchSecurity.com, a TechTarget site for Security
professionals.
A firewall is a set of related programs, located at a network gateway server, that protects the
resources of a private network from users from other networks. (The term also implies the security
policy that is used with the programs.) An enterprise with an intranet that allows its workers access
to the wider Internet installs a firewall to prevent outsiders from accessing its own private data
resources and for controlling what outside resources its own users have access to.
Basically, a firewall, working closely with a router program, examines each network packet to
determine whether to forward it toward its destination. A firewall also includes or works with a proxy
server that makes network requests on behalf of workstation users. A firewall is often installed in a
specially designated computer separate from the rest of the network so that no incoming request
can get directly at private network resources.
There are a number of firewall screening methods. A simple one is to screen requests to make sure
they come from acceptable (previously identified) domain name and Internet Protocol addresses.
For mobile users, firewalls allow remote access in to the private network by the use of secure logon
procedures and authentication certificates.
A number of companies make firewall products. Features include logging and reporting, automatic
alarms at given thresholds of attack, and a graphical user interface for controlling the firewall.
Router
On the Internet, a router is a device or, in some cases, software in a computer, that determines the
next network point to which a packet should be forwarded toward its destination. The router is
connected to at least two networks and decides which way to send each information packet based
on its current understanding of the state of the networks it is connected to. A router is located at any
gateway (where one network meets another), including each Internet point-of-presence. A router is
often included as part of a network switch.
A router may create or maintain a table of the available routes and their conditions and use this
information along with distance and cost algorithms to determine the best route for a given packet.
Typically, a packet may travel through a number of network points with routers before arriving at its
destination. Routing is a function associated with the Network layer (layer 3) in the standard model
of network programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a
switch that can perform routing functions.
An edge router is a router that interfaces with an asynchronous transfer mode (ATM) network. A
brouter
is
a
network
bridge
combined
with
a
router.
Hub
In general, a hub is the central part of a wheel where the spokes come together. The term is familiar
to frequent fliers who travel through airport "hubs" to make connecting flights from one point to
another. In data communications, a hub is a place of convergence where data arrives from one or
more directions and is forwarded out in one or more other directions. A hub usually includes a
switch of some kind. (And a product that is called a "switch" could usually be considered a hub as
well.) The distinction seems to be that the hub is the place where data comes together and the
switch is what determines how and where data is forwarded from the place where data comes
together. Regarded in its switching aspects, a hub can also include a router.
1) In describing network topologies, a hub topology consists of a backbone (main circuit) to which a
number of outgoing lines can be attached ("dropped"), each providing one or more connection port
for device to attach to. For Internet users not connected to a local area network, this is the general
topology used by your access provider. Other common network topologies are the bus network and
the ring network. (Either of these could possibly feed into a hub network, using a bridge.)
2) As a network product, a hub may include a group of modem cards for dial-in users, a gateway
card for connections to a local area network (for example, an Ethernet or a Token Ring), and a
connection
to
a
line
(the
main
line
in
this
example).
Switch
In a telecommunications network, a switch is a device that channels incoming data from any of
multiple input ports to the specific output port that will take the data toward its intended destination.
In the traditional circuit-switched telephone network, one or more switches are used to set up a
dedicated though temporary connection or circuit for an exchange between two or more parties. On
an Ethernet local area network (LAN), a switch determines from the physical device (Media Access
Control or MAC) address in each incoming message frame which output port to forward it to and out
of. In a wide area packet-switched network such as the Internet, a switch determines from the IP
address in each packet which output port to use for the next part of its trip to the intended
destination.
In the Open Systems Interconnection (OSI) communications model, a switch performs the layer 2 or
Data-Link layer function. That is, it simply looks at each packet or data unit and determines from a
physical address (the "MAC address") which device a data unit is intended for and switches it out
toward that device. However, in wide area networks such as the Internet, the destination address
requires a look-up in a routing table by a device known as a router. Some newer switches also
perform routing functions (layer 3 or the Network layer functions in OSI) and are sometimes called
IP switches.
On larger networks, the trip from one switch point to another in the network is called a hop. The time
a switch takes to figure out where to forward a data unit is called its latency. The price paid for
having the flexibility that switches provide in a network is this latency. Switches are found at the
backbone and gateway levels of a network where one network connects with another and at the
subnetwork level where data is being forwarded close to its destination or origin. The former are
often known as core switches and the latter as desktop switches.
In the simplest networks, a switch is not required for messages that are sent and received within the
network. For example, a local area network may be organized in a Token Ring or bus arrangement
in which each possible destination inspects each message and reads any message with its
address.
Circuit-Switching version Packet-Switching
A network's paths can be used exclusively for a certain duration by two or more parties and then
switched for use to another set of parties. This type of "switching" is known as circuit-switching and
is really a dedicated and continuously connected path for its duration. Today, an ordinary voice
phone call generally uses circuit-switching.
Most data today is sent, using digital signals, over networks that use packet-switching. Using
packet-switching, all network users can share the same paths at the same time and the particular
route a data unit travels can be varied as conditions change. In packet-switching, a message is
divided into packets, which are units of a certain number of bytes. The network addresses of the
sender and of the destination are added to the packet. Each network point looks at the packet to
see where to send it next. Packets in the same message may travel different routes and may not
arrive in the same order that they were sent. At the destination, the packets in a message are
collected and reassembled into the original message.
Point of presence: (POP)
A point-of-presence (POP) is an access point to the Internet. A POP necessarily has a unique
Internet Protocol (IP) address. Your Internet service provider (ISP) or online service provider (such
as AOL) has a point-of-presence on the Internet and probably more than one. The number of POPs
that an ISP or OSP has is sometimes used as a measure of its size or growth rate.
A POP may actually reside in rented space owned by the telecommunications carrier (such as
Sprint) to which the ISP is connected. A POP usually includes routers, digital/analog call
aggregators,
servers,
and
frequently
frame
relays
or
ATM
switches.
Network layer
In the Open Systems Interconnection (OSI) communications model, the Network layer knows the
address of the neighboring nodes in the network, packages output with the correct network address
information, selects routes and Quality of Service, and recognizes and forwards to the Transport
layer incoming messages for local host domains. Among existing protocol that generally map to the
OSI network layer are the Internet Protocol (IP) part of TCP/IP and NetWare IPX/SPX. Both IP
Version
4
and
IP
Version
6
(IPv6)
map
to
the
OSI
network
layer.
Domain:
A domain name locates an organization or other entity on the Internet. For example, the domain
name
www.totalbaseball.com
locates an Internet address for "totalbaseball.com" at Internet point 199.0.0.2 and a particular host
server named "www". The "com" part of the domain name reflects the purpose of the organization
or entity (in this example, "commercial") and is called the top-level domain name. The
"totalbaseball" part of the domain name defines the organization or entity and together with the toplevel is called the second-level domain name. The second-level domain name maps to and can be
thought of as the "readable" version of the Internet address.
A third level can be defined to identify a particular host server at the Internet address. In our
example, "www" is the name of the server that handles Internet requests. (A second server might
be called "www2".) A third level of domain name is not required. For example, the fully-qualified
domain name could have been "totalbaseball.com" and the server assumed.
Subdomain levels can be used. For example, you could have "www.nyyankees.totalbaseball.com".
Together, "www.totalbaseball.com" constitutes a fully-qualified domain name.
Second-level domain names must be unique on the Internet and registered with one of the ICANNaccredited registrars for the COM, NET, and ORG top-level domains. Where appropriate, a toplevel domain name can be geographic. (Currently, most non-U.S. domain names use a top-level
domain name based on the country the server is in.) To register a U. S. geographic domain name or
a domain name under a country code, see an appropriate registrar.
On the Web, the domain name is that part of the Uniform Resource Locator(URL) that tells a
domain name server using the domain name system (DNS) whether and where to forward a
request for a Web page. The domain name is mapped to an IP address (which represents a
physical point on the Internet).
More than one domain name can be mapped to the same Internet address. This allows multiple
individuals, businesses, and organizations to have separate Internet identities while sharing the
same Internet server.
To see the IP address for a domain name, (ping).
It may be worth noting that the domain name system contains an even higher level of domain than
the top-level domain. The highest level is the root domain, which would be represented by a single
dot (just as in many hierarchical file systems, a root directory is represented by a "/" ) if it were ever
used. If the dot for the root domain were shown in the URL, it would be to the right of the top-level
domain name. However, the dot is assumed to be there, but never shown.
Internet protocol
The Internet Protocol (IP) is 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 from 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 the order they were
sent in. 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 Internet Protocol 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.
Trend Micro
La Clave para
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es parte de la
familia integrada
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Micro
para protección
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que
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Requerimientos
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MB
de
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Nueva
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ServerProtect provee una tecnología antivirus de nueva generación para
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