This document is intended
to cover the questions usually asked by novices. As a side-effect,
it will help to the newsgroups from being cluttered by these
questions. It helps users with questions by providing instant
access to their answers; it helps other readers of the newsgroup,
who will have to read fewer of the questions they see over and
over again; it helps everyone by (hopefully) reducing traffic.
This FAQ tries to clear up a few things about the Internet,
and the trouble to connect to the Internet. Although the Intranet
is not different from the Internet in terminology, some specialties
are mentioned here.
This document should
help you find answers to frequently asked questions. Usually,
the answers are already available on the Net in one or more
detailed documents. In these cases, this document will tell
the reader where to find the information in question. Thus,
when possible, this document will only point you to another
document - that one may have the information you need, or it
may point you somewhere else. (This may seem annoying at first,
but offers multiple benefits. First, it reduces duplicated work.
Second, it increases your chances of finding the most current,
reliable information. Most importantly, it shows _how_ to find
the information you need rather than simply giving you answers.
"Teach a man to fish...")
This FAQ is purely
a volunteer effort. Although every effort has been made to insure
that answers are as accurate as possible, no guarantee is implied
or intended. The editor and contributors have developed this
FAQ as a service to the Internet. I hope you find it useful.
If you find any errors please report them to hermann@heimhardt.com.
Thank you.
Sorry folks, but this
document will appear only in English. Maybe there are some volunteers
that translate this to German. Please send your corrections,
questions, and comments to the editor at hermann@heimhardt.com.
Please indicate what version of this document you are referring
to (diffs are highly appreciated).
Where
can I get this FAQ ?
There is one way to
get a copy of this FAQ.
Via WWW:
http://heimhardt.com/htdocs/networkingfaq.html
Version 1.1 (HTML)
History stack:
Version 1.1 (HTML)
- reformatting and
rewriting of parts
- Intranet access
cookbook included
Version 1.01 (HTML)
- fixed error in cisco-networking-faq
pointer.
- created a history
stack instead of a history list
- changed some department
informations
- changed X.500 and
DCE Answers
Version 1.0 (HTML)
- created HTML document
- error fixing
- updates on various
infos
Version 0.5 (Draft)
ASCII groff source (never released)
Version 0.4 (Draft)
ASCII groff source
Version 0.3 (Draft)
ASCII groff source
- corrected minor
and major typos and groff formatting errors
- added/changed dns
subdomains
- added info to SCN
Section
Version 0.2 (Draft)
ASCII groff source
- corrected minor
and major typos
- corrected problems
in formatting the document
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Version
- new dns subdomains
added
Version 0.1 (Draft)
ASCII groff source
First of all: Read
your manuals. If you are sure, that the problem has nothing
to do with your local configuration consult your local network
provider. They should know how to fix the problem.
SECTION
1: WHAT IS... ?
Excerpt from: THE INTERNET
COMPANION - A beginners guide to "Global Networking"
by Tracy Laquey
- The Internet is
a loose amalgam of thousands of computer networks reaching
millions of people all over the world. Although its original
purpose was to provide researchers with access to expensive
hardware resources, the Internet has demonstrated such speed
and effectiveness as a communications medium that it has transcended
the original mission. Today it's being used by all sorts of
people -- educators, librarians, hobbyists, and businesspeople
-- for a variety of purposes, from communicating with each
other, to accessing valuable information and resources.
- Excerpt from RFC1462:
A commonly asked question is "What is the Internet ?"
The reason such a question gets asked so often is because
there's no agreed upon answer that neatly sums up the Internet.
The Internet can be thought about in relation to its common
protocols, as a physical collection of routers and circuits,
as a set of shared resources, or even as an attitude about
interconnecting and intercommunication. Some common definitions
given in the past include:
- a network of networks
based on the TCP/IP protocols,
- a community of people
who use and develop those networks,
- a collection of
resources that can be reached from those networks.
Today's Internet is
a global resource connecting millions of users that began as
an experiment over 20 years ago by the U.S. Department of Defense.
While the networks that make up the Internet are based on a
standard set of protocols (a mutually agreed upon method of
communication between parties), the Internet also has gateways
to networks and services that are based on other protocols.
DNS stands for Domain
Name Service. The purpose of domain names is to provide a mechanism
for naming resources in such a way that the names are usable
in different hosts, networks, protocol families, internist,
and administrative organizations.
Name service is a network
service providing name-to-address translation. Such service
can be achieved in a number of ways. For a simple networking
environment, it can be accomplished with a single central database
containing name-to-address correspondence for all the pertinent
network entities, such as hosts.
The name service at
each domain is assumed to be provided by one or more name servers.
A name server is a
network service that enables clients to name resources or objects
and share this information with other objects in the network.
This in effect is a distributed data base system for objects
in a computer network.
The World-Wide-Web
is a graphical Internet service with some very nice linking
abilities. These features have made the Web the fastest growing
Internet Service. The Web can link from any point in a document
or image to any point in another document. However, you need
a browser with a graphical user interface (GUI) like Netscape
or Mosaic, or an ASCII browser like Lynx to take advantage from
the Web. In fact you can access every Internet service (ftp,
telnet, news, archie, ...) from the Web.
Usenet is a worldwide
network of computers that run, among other services, the News
software. It is a public forum for the exchange of ideas in
the form of articles that are broadcast to member sites. Net
users can post articles, reply by mail or send follow-up articles
to previous ones, or simply read the News using the netnews
programs (nn, tin, trn, trumpet, ...). To bring structure in
the collection of users and their ideas, news articles are classified
into newsgroups.
FTP stands for file
transfer protocol. FTP allows you to copy files from a remote
computer to your local host and vice versa. FTP-Clients are
available not only for UNIX Systems, but also for PCs, BS2000-Hosts,
MVS-Hosts ...
A router is a network
"relay" that uses a protocol beyond the data-link
protocol to route traffic between LANs and other network links.
This approach creates two separate subnets and uses routing
to filter the packets between them. Routers talk to each other
using a routing protocol. The TCP/IP family of protocols has
a bunch of routing protocols, such as RIP, EGP, BGP, OSPF, and
dual IS-IS.
For further info please
refer to the
CISCO Networking FAQ
Routing binds networks
together. Without routing the network traffic would be limited
to a single physical network. Routing allows traffic from your
local network to reach its destination somewhere else in the
world - perhaps after passing through many intermediate routers
and networks. On a UNIX-Host you can show all routes using the
netstat command:
root@hellraiser.rs.sni.de$ netstat -rn
Routing tables
Destination Gateway Flags Refcnt Use Interface
127.0.0.1 127.0.0.1 UH 1 0 lo0
default 149.202.66.1 UG 2 254210 et0
149.202 149.202.66.5 U 14 3495918 et0
The output of the netstat
command shows that there are three routes defined: One route
to the local host (127.0.0.1), one default route (default) and
a route to the network 149.202.x.x (149.202). There are different
Gateways to those networks. These gateways are routing IP packets
to their destinations.
What
is a default-route ?
A default route is
used whenever there is no specific route to a destination, and
it is often the only route you need. If your network has only
one gateway, use a default route to direct all traffic bound
for remote networks through that gateway.
What is
a Firewall ?
A firewall computer
provides strict access control between your systems inside the
company and the outside world. A firewall system replaces an
IP router with a multi-homed host that does not forward packets.
Firewalls do sever the connection between networks. To provide
the network behind the firewall with some level of network connectivity,
the firewall performs certain unique functions. To minimize
the inconvenience caused by a firewall, the system must do many
more things, than a router does. The firewall must provide:
- DNS for the outside
world.
- E-Mail forwarding
- FTP service
- Telnet service
- WWW service
For further info please
refer to
The firewall FAQ
What
is SMTP ?
SMTP stands for SIMPLE
MAIL TRANSFER PROTOCOL.
Excerpt from RFC821:
The objective of Simple Mail Transfer Protocol (SMTP) is to
transfer mail reliably and efficiently. SMTP is independent
of the particular transmission subsystem and requires only a
reliable ordered data stream channel. An important feature of
SMTP is its capability to relay mail across transport service
environments. A transport service provides an interprocess communication
environment (IPCE). An IPCE may cover one network, several networks,
or a subset of a network. It is important to realize that transport
systems (or IPCEs) are not one-to-one with networks. A process
can communicate directly with another process through any mutually
known IPCE. Mail is an application or use of interprocess communication.
Mail can be communicated between processes in different IPCEs
by relaying through a process connected to two (or more) IPCEs.
More specifically, mail can be relayed between hosts on different
transport systems by a host on both transport systems.
For further info please
refer to
RFC821
What
is MIME ?
MIME stands for Multipurpose
Internet Mail Extensions.
Excerpt from RFC1521:
STD 11, RFC822 defines a message representation protocol which
specifies considerable detail about message headers, but which
leaves the message content, or message body, as flat ASCII text.
This document redefines the format of message bodies to allow
multi-part textual and non-textual message bodies to be represented
and exchanged without loss of information. This is based on
earlier work documented in RFC 934 and STD 11, RFC 1049, but
extends and revises that work.
For further info please
refer to
RFC1521
What
is X.400 ?
X.400 is the short
name for the set of standards from ISO and the ITU that describe
a mail service. It is the only non-proprietary standard for
interchange of electronic mail that has the sanction of an official
standards body. (ITU-TS, the International Telecommunications
Union Telecommunication Standard Sector, was formerly named
CCITT).
It currently exists
in 3 flavors:
- X.400/84: This is
what most implementations today in fact run. It was documented
in the "Red Book" series from ITU-TS.
- ISO MOTIS/86 (mostly
dead): This was the first attempt from ISO to agree to what
ITU-TS had done. It died at the DIS stage. It contains some
elements you need in order to conform to the European functional
profiles and make manageable systems from the 1984 version,
like domain-internal trace and the ISO6937 body part.
- X.400/88: This is
documented in the "Blue Book" series. Most people
seem to think that this is a great improvement over 84, but
the number of systems implementing it has been underwhelming.
This one is also an International Standard by ISO.
What
is X.500 ?
Excerpt from RFC1330:
X.500 is a CCITT/ISO standard which defines a global solution
for the distribution and retrieval of information (directory
service). The X.500 standard includes the following characteristics:
- decentralized management,
- powerful searching
capabilities,
- a single global
namespace,
- a structured framework
for the storage of information.
The 1988 version of
the X.500 standard specifies four models to define the Directory
Service: the Information Model, the Functional Model, the Organizational
Model and the Security Model. As is the nature of International
standards work continues on the 1992 X.500 standard agreements.
For further info please
refer to
RFC1330
DCE (Distributed Computing
Environment) is a future-oriented standard for distributed applications
and is offered by the OSF (Open Systems Foundation).
Used in heterogeneous
network environments (LAN or LAN segment coupled via WAN basing
on IP using IPX25 or IP-ISDN) DCE offers a state-of-the-art
of fast and distributed communication across a network. The
remote procedure call of DCE (DCE RPC) makes the distribution
of the applications a fast and secure way of computing. The
thread architecture increases the performance within the client
and server processes by parallelizing the working code.
A high standard of
security for the applications (client and server) within the
network is gained through DCE SECURITY, a sophisticated way
of authenticating the user (Berbers) and authorizing his access
to all objects that are to be protected. An additional data
encryption makes communications even more secure against eavesdropping
on the very hardware level.
The transparent access
to all resources available on DCE hosts in the network is organized
using the Cell Directory Service (CDS). Replication allows load
balancing of the most important DCE servers (CDS and SEC) on
multiple machines (you can have a read-only copy of the CDS
name space or the security registry to fasten the access to
the data or obtain higher security and avilability, e.g.).
Back
to WHAT IS ... ? or Back to the TOC
SECTION
2: WHERE CAN I GET... ?