A plus 220-1001 – Exam Objective 2.5
A+ Exam Objective 2.5
2.5 Summarize the properties and purpose of services provided by networked hosts.
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we will look at some of the specific services provided by network servers and
other network hosts. We will examine the purpose and properties of various
servers, internet appliances, and legacy systems.
Specialized servers are the key to efficient web content
delivery for mail, file print, addressing, and name services as well as user
authentication. We will now break them down.
A Web server is used by companies to deliver web based content
over HTTP. This can be done privately, in the case of an internally accessed
company webpage, or publicly over the internet.
A File server is primarily used to establish a central location
where users can store and share content such as documents, media files, and
spreadsheets. The computer hosting the service is attached to the local
network. An NAS (Network Attached Storage) device is often used in this type of
application. However, this is not the same as an internet based file server which
uses the FTP protocol and is accessed using FTP client software.
A Print server is a network connected, shared device that
manages and distributes print “jobs” to the printers it controls. Users and
administrators can manage print jobs through the queue, which displays all jobs
received by the server and their status. A single user can manage their own
jobs and an administrator can manage all jobs. While print servers as computers
are still a part of many networks, stand-alone wired and wireless network based
printers exist that contain built-in print servers.
A DHCP server is responsible for delivering IP addressing and
related configuration information to its clients using the Dynamic Host
Configuration Protocol. This service has saved countless man-hours and address
duplications. The DHCP server uses an assigned address range, called a scope, in
order to provide addresses to hosts without duplication along with any other
necessary information such as subnet masks and gateway information. These
addresses are leased to the host for a predefined period of time, after which
they are refreshed or renewed.
DNS servers have made user interaction on the internet
dramatically simpler. DNS servers translate Fully Qualified Domain Names (FQDN)
into IP addresses. Once a server performs this translation, the translation
information is stored in its database for quicker access. The DNS (Dynamic Name
Server) is joined to the Dynamic Name System which allows it to consult with
other DNS servers when necessary. A new server will do this frequently but over
time, less frequently as it consults its local database first.
A Proxy server is a dedicated computer or network device that
handles all external requests made by users on the network. When the Proxy
server receives a request for a webpage, it checks its internal cache of
previous requests and if found delivers the content quickly, providing improved
performance. If the content is not cached, the Proxy will either connect to or
act as a firewall and perform private to public NAT (Network Address
Translation). The Proxy is capable of masking the client IP address, blocking
specified traffic, and filtering out malicious traffic.
A Mail server can conceptually be considered an email server as
it handles email. Email is customarily sent using an email client software
package, which allows emails to be composed and sent. This same program will
also check your mail server for any inbound messages. There are two main types
of mail servers: incoming and outgoing. The outgoing server will use the Simple
Mail Transport Protocol (SMTP) to send traffic to other mail servers en route
to the destination. Delivery to the destination client is achieved using one of
two incoming server types: POP3 (Post Office Protocol 3) and IMAP (Internet
Message Access Protocol). To summarize, you send email using an SMTP configured
mail server and receive email using either a POP3 or IMAP server. These can be
separate servers or hosted on the same server.
An Authentication server is usually an application running on a
server, such as Active Directory for example. This internet or network
appliance handles authentication by providing a user, or device, access to
designated resources on the network as determined by the administrator.
Syslog is a protocol that allows network devices to send TCP
messages to a Syslog server regarding network events such as logon/logoffs,
errors, and maintenance. The syslog server maintains a database of these
devices and events for use by administrators.
The Unified Threat Management (UTM) is a way to reduce cost and
administrative overhead by combining multiple security features, such as
router, firewall, and content filters, into a single hardware appliance in order
to protect the network from unwanted or malicious traffic. The UTM is generally
positioned between the Internet and the protected network. Here is a look at
some of the possible elements.
The Intrusion Detection System (IDS) is one of the earliest
network intrusion monitoring devices and is often found as a feature of a UTM,
router, and server. It comes in two primary configurations, either as a network
based NIDS, that will monitor an entire network, or as a Host based solution
HIDS, when individual workstations have this capability. The IDS signals an
alarm when suspicious activity is detected. However, this solution lacks the
capability to block traffic.
An Intrusion Protection System (IPS) takes the IDS concept and
evolves it to detect an alert condition before it enters the network and drops
or blocks the connection. This is an effective approach but is not a
replacement for IDS. The IPS is vulnerable to encrypted network traffic, making
a layered approach the optimum solution as opposed to “either or”.
End-point management server
Endpoints are any devices, such as computers, tablets,
smartphones, and laptops, that require network access. The endpoint server inspects
the endpoints to see if they meet the established policy criteria before they
can access the network. Endpoint condition includes the status of software
updates/patches and anti-malware updates.
Legacy / embedded systems
When considering network servers and devices, remember that you
will encounter networks that are comprised of a mix of new(er) and legacy (= old)
hardware. A single computer hosting multiple services, such as file and print
or web and email, is not uncommon. Also, you will encounter services that are
embedded in the firmware. Many routers, particularly the consumer grade or SOHO
designs, have services such as DHCP and Proxy built in.
That’s it for Objective 2.5. Good Luck on the test. You are getting closer…
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