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Diese Seite soll einen
kleinen Überblick zum Thema Networking bieten.
folgende Informationen sind abrufbar:
Network Calculators
IP addresses and Subnetting
TCP/IP ports
Addressing and Subnetting on the Near Side of the Net
The Domain Name System (DNS)
Firewall security
Goto Whoix? - das ultimative Domain-Namen Portal
Oesterreichisches ADSL-Forum
Netzmafia-Skriptensammlung
 Network Calculators
Calculating IP subnet masks is one of the most basic yet most error-prone networking tasks.
This site's subnet mask calculator takes the guesswork out of the process with a
fill-in-the-blanks format: Users simply enter the network address, number of subnets or
hosts per subnet, and presto the site calculates the correct subnet masks to use.
The site also distinguishes between network ID and host ID portions of IP address/subnet mask combinations.
IP addresses and Subnetting
The following gives an introduction to IP addresses and
subnetting on local area networks. If you want to find out about the advantages
of using private network IP addresses on you local area network, or what
subnetting can do for you, the explanation is here. You can also find the recipe
for how you calculate a subnet mask, a network address and broadcast address.
However, the course also offers a fast track to getting the advantages of
subnetting on local area networks without having to do all the calculations
yourself. If this is what you are looking for, you might want to jump directly
to the last chapter in this course: ‘The fast track to the advantages of
subnetting'.
(full document as PDF)
TCP/IP
ports
Any single machine on the Internet is addressed and
identified by a unique IP number like: 207.71.92.193. That particular IP is the
Internet address of the machine running a web server that your web browser
connected to in order to view the contents of this web site.
But the machine offers more than just web services. It also has an FTP server
offering files, an SMTP server supporting our eMail post office, and a POP3
server allowing our employees to pickup their eMail. Yet all of these various
servers are running within a single machine located at a single IP address. So
how do we know which of these servers should handle a connection request from
another computer on the Internet ?
The answer, of course, is
Ports.
A
PORT is nothing more than the final portion of the
destination
address for any piece of Internet traffic.
Standard port numbering conventions have been
widely adopted to allow specific client programs, like a web browser or eMail
client, to connect to their proper counterpart servers on a remote machine. For
example, web browsers typically connect to a web server using port 80 and secure
encrypted web connections generally occur on port 443. Email clients pickup
incoming mail from a server at port 110 and deliver outbound mail to a server at
port 25. FTP clients usually connect to FTP servers on port 21.
TCP ports are numbered 1 through 65535. Servers accepting
inbound connections have traditionally "listened for connections" on
the lower-numbered ports 1 through 1023 which are therefore known as the
"system" ports. Client computers originating outbound connections
generally grab any free port above 1023 as their "source port" and
specify the destination machine's IP address and the destination port for the
service they wish to solicit from the remote machine.
Since server software opens and listens for connections on
well known port numbers, every Internet machine with software servers has an
"open port profile" describing the services that are being made
available by that machine. This is relevant to issues of security because it's
possible to scan across all of a machine's potential ports to find those that
are "open" and "listening" for connections. As the diagram
above shows, when a scanner sweeps past such a machine and discovers open ports
21, 25, 80, and 110, it concludes that this machine contains four servers for
file transfer (FTP), inbound eMail (SMTP), web (HTTP) and outbound eMail (POP3).
Each open port on a machine creates a
potential point of
attack for an internet intruder.
(full document as PDF)
Addressing and Subnetting on the Near Side of the
Net
This document is designed to give the reader a reasonable
working knowledge of TCP/IP subnetting, addressing, and routing. It is not
intended to be complete, or to cover all issues. This is targeted toward LAN
administrators just moving to TCP/IP, however it should help anyone who wants to
know a little (more) about how TCP/IP works. This document does not, generally,
apply to dial-up SLIP/PPP connections.
(full document as PDF)
The Domain Name System (DNS)
The following is a general, non-technical introduction to the
Domain Name System and how it works on the Internet. If you are looking for
specific information on how the domain name space is organised, how domains can
be acquired, or how DNS servers do what they do, you might want to go directly
to ‘More about the Domain Name System (DNS)’.
(full document as PDF)
Firewall security
This overview of Firewall security will give you a basic
understanding of the role of firewalls in the protection of local networks, as
well as a brief description of how firewalls work and why it is important that a
company has a carefully planned security policy.
For a more thorough walkthrough of the actual techniques behind firewalls you
may want to turn to ‘More about Firewall security’.
(full document as PDF)
Domain
Check
Offers free Domain-Name Search/Check and Info who has
registered a domain you are searching for
Goto Whoix? -
the ultimate
Domain-Name Portal
Oesterreichisches ADSL-Forum
Das Oesterreichische ADSL-Forum ist ein Treffpunkt mit
öffentlichen Message-Boards für alle, die auf dem Gebiet High-Speed-Internet
Erfahrungen austauschen, Fragen stellen, Antworten geben oder einfach ihre
Meinung kundtun wollen!
Netzmafia
Hier finden Sie viele per WWW verfügbare Skripten sowie
aktuelle Erweiterungen zu den Themen:
Datenkommunikation,
Netze
HTML, Multimedia
Programmieren
Betriebssyteme
Hardware
Glossare, RFCs
Etliche Skripte ergänzen sich gegenseitig, z. B. 'Modem-Technik',
'Computernetze' und die Internet-Themen oder auch 'Einführung in
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und 'Internet.
Die Skripten bieten vielfach auch Hintergrundinformationen und
Praxistips.
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