Transcript Network Technology Foundations

Network Technology
Foundations
© 2004 ProsoftTraining
All Rights Reserved
Lesson 3:
Internetworking Servers
Objectives
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Identify and describe the functions and features
of various internetworking servers
Describe how each type of internetworking
server use TCP/IP suite protocols
Describe access-security features of an HTTP
server
Define MIME, and explain how MIME types are
used by HTTP and mail servers
Describe the functions of DNS
Define “daemon” and identify the functions of
the Internet-related daemons
File and Print Servers
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File servers — network servers that store data
files and programs that can be shared by network
users
Print servers — network servers that allow
multiple users to send print jobs to the same
physical printer
Line Printer/Line Printer Daemon (LPR/LPD) —
printing protocol in UNIX that allows users to
submit print jobs to network printers
HTTP Server Essentials
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The Web — a collection of computer systems
running the HTTP service
Web server — has access to HTML documents
that are returned to a client in response to a
request
Web gateway — a program on a server that is
activated based on a client request:
• Server passes the request to the program
• Program processes the request
• Server returns the program output to the
client
HTTP Server Essentials (cont’d)
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HTTP Servers and MIME
• Multipurpose Internet Mail Extensions (MIME)
— allow HTTP and e-mail attachments to
identify the files they must use
• MIME types — identify the contents of a file so
browsers can display the contents properly
HTTP Server Essentials (cont’d)
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Additional HTTP server considerations:
• HTTP servers work with a variety of operating
systems
• Permissions — restrict or allow access to
system resources
 Operating system permissions usually
override HTTP server permissions
• Access control — specifies who has access to
system resources
HTTP Server Essentials (cont’d)
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Additional HTTP server considerations:
• Aliases (or virtual directories)
 Flexible mapping of URL path names to file
names
• Logging — a log of requests handled by the
server
 Access data
 Referrer data
 Error data
HTTP Server Essentials (cont’d)
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Additional HTTP server considerations:
• Monitor server and network bandwidth use
 Helps maintain consistent performance
 Helps to identify bottlenecks
 Helps to create a baseline against which
future network activity can be compared
Database Server
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Database — a file that stores information in a
series of tables and columns
Relational database — a database consisting of
two or more tables related by a common field
Database server — a server that presents
relational databases and makes it possible for
remote individuals to access the data
All database servers use SQL to create, maintain
and query databases
Proxy Server
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Proxy server — an intermediary between a
network host and other hosts outside the network
Proxy servers:
• Provide enhanced security
• Manage TCP/IP addresses
• Speed Internet access by caching Web
documents
• Replace network IP address with another,
contingent address
Mail Server
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Mail servers store/forward e-mail messages using
several protocols:
• SMTP — used to send messages
• POP3 — used to store and forward messages
(forces a user to download messages before
managing them)
• IMAP — used to store and forward messages
(allows a user to browse and manage
messages remotely)
MIME is used to transmit files with e-mail
Instant Messaging (IM)
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Instant messaging runs on a mail server
Use instant messaging to:
• Type and view messages sent to one or more
recipients
• View the responses immediately
Instant messages can be sent only to contacts
who are currently online
Mailing List Server
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Forwards an e-mail message to every member on
a distribution list
Mailing List Manager (MLM) — the interface that
allows you to configure a mailing list server
Public versus private mailing lists
Examples of public mailing lists:
• LISTSERV
• Majordomo
Mailing List Server (cont’d)
Media Server
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Provides streaming audio and video over a
network
Uses UDP ports and buffers to achieve the effect
of a real-time connection
• UDP is a connectionless protocol
• Buffer — cache of memory that stores
frequently-used data to allow for faster access
times
DNS Server
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DNS — mechanism used on the Internet to
translate host computer names into IP addresses
• www.ciwcertified.com = http://12.42.192.73
Hosts file — file referenced locally by applications
and commands for name-to-address resolution
DNS Server (cont’d)
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DNS hierarchy:
• Root-level domain — the top of the hierarchy
that contains entries for each top-level domain
• Top-level domain — consists of categories
found at the end of domain names
• Second-level domain — includes the
businesses and institutions that register their
domain names with the top-level domains
DNS Server (cont’d)
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DNS components:
• Name server — server that supports name-toaddress translation and runs the DNS service
• Name resolver — software that uses the
services of one or more DNS servers to resolve
an unknown request
DSN server types: root, primary, secondary,
caching-only, forwarding
DNS records — entries in DNS database that
provide additional routing and resolution
information
DNS Server (cont’d)
Domain name space
.(root)
ie
se
com
mx
net
ch
xyz
user1
iso
ftp
user2
www
DNS Server (cont’d)
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nslookup
• Used to query Internet domain name servers
to learn name-to-IP-address mappings
• Example of nslookup one-time command:
 nslookup www.ciwcertified.com
• Used interactively by typing:
 nslookup
FTP Server
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Allows the transfer of large files between file
servers in real time
Files of 2 MB or greater should be transferred by
means of FTP
Sending files by means of FTP is faster than with
e-mail and HTTP
News Server
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Uses NNTP
Written text output
Multiperson input
Allows users to post information any time
Can be used to create secure newsgroups by
enabling user-specific password protection or
through an SSL session
Certificate Server
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Validates, or certifies, encryption keys
• Keys — strings of text generated from
encryption algorithms that allow you to secure
communications for a company or group of
users
Directory Server
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Identifies all resources on a network, then makes
them available to authenticated users
Enables a company to reuse information in its
directory
Avoids re-entry of user information for applications
that require it
Helps administrators manage applications and users
Helps users locate other users or e-mail addresses
Locates and manages all company accounts
Allows users inside and outside the network to use
the service
Maintains a single database of e-mail contacts
Directory Server (cont’d)
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Directory server protocols:
• X.500 — used to manage user and resource
directories
• X.500 offers:
 Scalability
 Synchronization
 Replication
• LDAP — TCP/IP protocol that allows
communication on both intranets and the
Internet
Catalog, Fax and
Transaction Servers
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Catalog servers:
• Index databases, files and information and
allow keyword, Boolean and other searches
• Use robots to automate indexing process
Fax servers:
• Provide a centrally located fax system
• Consist of a bank of fax/modems
Transaction servers:
• Guarantee that all required databases are
updated when a transaction takes place
The Internet Daemon:
inetd and xinetd
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Daemon — UNIX program initiated at startup;
runs in the background until required
inetd — daemon that listens on specified TCP
and UDP ports (0 to 1023) and launches
services to support requests it receives
xinetd — modified form of inetd that is more
secure; provides more control over how
daemons are run and which remote systems
can use a particular daemon
inetd and xinetd can create security problems
because they have root permission; they can
also deplete system resources because they
spawn new processes each time they are used
Mirrored Server
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Provides data redundancy by writing to two
physical hard drives each time a write operation
occurs
When a write request is issued:
• Data is written to the primary drive
• Data is copied to the mirrored drive
If one drive fails, all data is protected from loss
Mirrored Server (cont’d)
Main Serv er's
Hard Driv e
File 1
File 2
File 3
Mirrored Serv er's
Hard Driv e
Choosing Web Server Products
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Apache Web server
• Used by more than half of all Web sites
• Supports UNIX and Windows XP
• Available free of charge
Microsoft IIS
• Includes HTTP, FTP, NNTP, SMTP, certificate,
ASP, index (catalog) and transaction services
• Allows you to use a remote server to store and
retrieve files
Choosing Web Server Products
(cont’d)
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Lotus Domino series
• Includes all the most-used servers, including
certificate, HTTP, SMTP and FTP
• Serves applications over intranets and the
Internet
• Supports Java servlets as a preferred database
connection method
• Supports several operating systems including
AS/400, S/390, OS/2, Windows servers,
Solaris, AIX and HP-UX
Choosing Web Server Products
(cont’d)
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Sun ONE servers
• Support many platforms, including OS/2,
Windows NT and 2000, Solaris, AIX, HP-UX,
AS/400 and S/390
• Include servers with Server-Side JavaScript
interpreters
• Can use JavaScript to connect to databases
• Can implement other server-side scripting
applications
Choosing Web Server Products
(cont’d)
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Java software and Web servers:
• Java servlet — Java code that is compiled and
runs solely on Web servers
• Servlets allow:
 Chaining
 Connections to databases
 Near-universal support on systems