Networking

Networking
http://www.netfilter.org/documentation/HOWTO//networking-concepts-HOWTO.txt
 Computers need to be networked when data stored on one
machine is required for use on another.
 A typical arrangement for a small office networked system is 4
machines connected together on a simple network, with one of
the machines adopting the role of a "server". The server is either
a dedicated or non-dedicated machine, which co-ordinates disk
and file sharing on the network.
 Typical network server software could be a Windows shared
folder for a simple peer-to-peer system. Alternatives include
Novell Netware, Microsoft Windows Server or Linux/Samba for a
secure server.

+==========T=============T=============T==========T==========+
| | | |
+---+ +---+ +---+ +---+
| | | | | | | |
+---+ +---+ +---+ +---+
 In a simple peer-to-peer system, the drive space on each
machine is often shareable, the server machine is also
used as a workstation as well, and there is virtually no
security for the files.
 However, it is a very inexpensive system to set up and is
ideal for circumstances where security is unimportant.
 Where the server is a dedicated machine on the network,
client machines access files and resources on the server,
and do not share space on their own disks. This system is
known as Client-Server, and would typically be
implemented by software such as Netware and NT Server.

Network card
 a network card is needed to make a physical connection by wire
or wireless
 an example of network card connections is shown here:
http://en.wikipedia.org/wiki/Rj45#RJ45
+------+
| |
| ____ |
|| ||
|| | | ---twisted pair connection (Ethernet via RJ45)
||____||
| __ |
| / |
|| O || ---WiFi connection
| __/ |
+------+

http://en.wikipedia.org/wiki/File:Network_card.jpg

+======T========T==========T==========T
| | | |Gateway
+---+ +---+ +---+ |192.168.0.1
| 5 | | 6 | | 7 | +----+---------+
+---+ +---+ +---+ | Firewall |
| Router box |
192.168.0.x +--+-----------+
|143.53.123.77
|
|
|
|143.53.123.100
/----------- +-----+-----+
///// | |
| Internet | | ISP |
| (LINX) +--+ Main |
///// | Router to |
-----------/ | Internet |
+-----------+

LINX
https://www.linx.net/index.html

There are 3 basic methods of sending packets of
data across a network.
 circuit switching. Dedicated line during the
communication, ie telephone
 message switching. Data is sent complete from node
to node. Store and forward.
 packet switching. Data is broken up into small
packets, sent by best route, and reassembled at
receiver end.
 IP uses packet switching.

Protocols
 There are a number of methods for passing data
from machine to machine across a network.
 Packets of data are enclosed by other pieces of
information, which provide the network
hardware with enough facts to send the data to
the correct destination.
 Commonly referred to as protocols, there are a
significant number used on modern networks.

 IP - Internet protocol. The protocol used on UNIX
systems, and significantly the Internet itself.
 AppleTalk - Apple's protocol
 NetBEUI- Microsoft's protocol
 IPX - Internet packet exchange. Novell's own
protocol used on Netware systems
Ethernet - the 'frame' that 'carries' the protocol
http://en.wikipedia.org/wiki/Ethernet

OSI
Layer
Apple
Computer
Banyan
Systems
DEC
DECnet
IBM
SNA
Microsoft
Networking
Novell
NetWare
TCP/IP
Internet
Xerox
XNS
OSI
Protocols
Application
Layer 7
Application Programs and Protocols
for file transfer, electronic mail, etc.
Presentation
Layer 6
AppleTalk
Filing
Protocol
(AFP)
Remote
Procedural
Calls
(Net RPC)
Network
Management
Network
Application
Transactio
n
Services
Presentati
on
Services
Server
Message
Block
(SMB)
NetWare
Core
Protocols
(NCP
(Telnet, FTP,
SMTP, etc.)
Control
and
Process
Interactio
n
ISO
8823
Session
Layer 5
AppleTalk
Session
Protocol
(ASP)
Session
Data
Flow
Control
Network
Basic
Input/Output
System
(NetBIOS)
Network
Basic
Input/Output
System
(NetBIOS)
ISO
8327
Transport
Layer 4
AppleTalk
Transaction
Protocol
(ATP)
VINES
InterProcess
Communicati
ons
(VIPC)
End
Communicati
ons
Transmissi
on
Control
Network
Basic
Extended
User Interface
(NetBEUI)
Sequenced
Packet
Exchange
(SPX)
Transmission
Control Protocol
(TCP),
(UDP)
Sequence
d
Packet
Protocol
(SPP)
ISO
8073
TP0-4
Network
Layer 3
Datagram
Delivery
Protocol
(DDP)
VINES
Internet
Protocol
(VIP)
Routing
Path
Control
Internet
Packet
Exchange
(IPX)
Internet
Protocol
(IP)
Internet
Datagram
Protocol
(IDP)
ISO
8473
(CLNP)
Data Link
Layer 2
Network Interface Cards: Ethernet, Token-Ring, ARCNET, StarLAN, LocalTalk, FDDI, ATM, etc.
NIC Drivers: Open Datalink Interface (ODI), Network Independent Interface Specification (NDIS)
Physical
Layer 1
Transmission Media:
Twisted Pair, Coax, Fiber Optic, Wireless Media, etc.
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Internet Protocol Addresses.
Internet Protocol Addresses are composed of four bytes.
The convention is to write addresses in what is called `dotted
decimal notation'. In this form each byte is converted to a decimal
number (0-255) dropping any leading zero's unless the number is
zero and written with each byte separated by a `.' character.
By convention each interface of a host or router has an IP address.
It is legal for the same IP address to be used on each interface of
a single machine in some circumstances, but usually each
interface will have its own address.

IPv6
 IPv6 is the shorthand notation for version 6 of the Internet
Protocol.
 IPv6 was developed primarily to overcome the concerns in the
Internet community that there would soon be a shortage of IP
addresses to allocate.
 IPv6 addresses are 16 bytes long (128 bits).
 IPv6 is a new version of IP which is designed to be an
evolutionary step from IPv4.
 It is a natural increment to IPv4.
 It can be installed as a normal software upgrade in internet
devices and is interoperable with the current IPv4.
 IPv6 address: 5F05:2000:80AD:5800:0058:0800:2023:1D71

Internet Protocol Networks
 Internet Protocol Networks are contiguous sequences of IP
addresses.
 All addresses within a network have a number of digits
within the address in common.
 The portion of the address that is common amongst all
addresses within the network is called the `network portion'
of the address.
 The remaining digits are called the `host portion'.
 The number of bits that are shared by all addresses within
a network is called the netmask and it is role of the
netmask to determine which addresses belong to the
network it is applied to and which don't.

Host Address 192.168.110.23
Network Mask 255.255.255.0
Network Portion 192.168.110.
Host portion .23
----------------- ---------------
Network Address 192.168.110.0
Broadcast Address 192.168.110.255
 Any address that is 'bitwise anded' with its
netmask will reveal the address of the network
it belongs to.
 The network address is therefore always the
lowest numbered address within the range of
addresses on the network and always has the
host portion of the address coded all zeroes.

broadcast address
 The broadcast address is a special address that every host on the
network listens to in addition to its own unique address. This address
is the one that datagrams are sent to if every host on the network is
meant to receive it simultaneously, like routing information and
warning messages.
 There are two commonly used standards for what the broadcast
address should be.
 The most widely accepted one is to use the highest possible address
on the network as the broadcast address. In the example before this
would be 192.168.110.255.
 Other sites have adopted the convention of using the network address
as the broadcast address. In practice it doesn't matter very much
which you use so long as every host on the network is configured with
the same broadcast address.

classes
For administrative reasons some time early in the development of the IP
protocol some arbitrary groups of addresses were formed into networks and
these networks were grouped into what are called classes. These classes
provide a number of standard size networks that could be allocated. The
ranges allocated are:
+--------------------------------------------------------+
| Network | Netmask | Network Addresses |
| Class | | |
+--------------------------------------------------------+
| A | 255.0.0.0 | 0.0.0.0 - 127.255.255.255 |
| B | 255.255.0.0 | 128.0.0.0 - 191.255.255.255 |
| C | 255.255.255.0 | 192.0.0.0 - 223.255.255.255 |
|Multicast| 240.0.0.0 | 224.0.0.0 - 239.255.255.255 |
+--------------------------------------------------------+
What addresses you should use depends on exactly what it is
that you are doing.

a private network
If you are building a private network and you never intend that network to be connected
to the Internet then you can choose whatever addresses you like. However, for safety
and consistency reasons there have been some IP network addresses that have been
reserved specifically for this purpose. These are specified in RFC1597 and are as
follows:
+---------------------------------------------------------+
| RESERVED PRIVATE NETWORK ALLOCATIONS |
+---------------------------------------------------------+
| Network | Netmask | Network Addresses |
| Class | | |
+---------------------------------------------------------+
| A | 255.0.0.0 | 10.0.0.0 - 10.255.255.255 |
| B | 255.255.0.0 | 172.16.0.0 - 172.31.255.255 |
| C | 255.255.255.0 | 192.168.0.0 - 192.168.255.255 |
+---------------------------------------------------------+
You should first decide how large you want your network to be and
then choose as many of the addresses as you require.

What is MS Windows networking?
Drive letters are only of relevance within a MS Windows environment,
and has no relevance on other Operating Systems. In other words it's
ONLY a MS way of assigning a disk resource.
It is a drive letter assigned LOCALLY to a LAN filespace resource. This
drive letter is only valid for use on the LAN and has NO relevance on
WANs, including the Internet.
If some disk space is made available to users, and the user has
permission to access this resource, then on a MS Windows machine
only, and assuming the correct network protocols are being used, then
this disk space can be assigned to a drive letter.

dforbes on 'SATURN (nthomes.inf.brad.ac.uk)' is assigned to drive z:
in this example the contents of 'dforbes' filespace on the server called
'SATURN' is assigned to a drive letter z:.
So drive z: is only of relevance to 'dforbes' on his machine. Other users
can also be using a drive z:, but their z: will contain completely different
files from the 'dforbes' user filestore area.
... One drive letter ..... different filestores .... lots of confusion.
To view all workgroups and domains on the LAN, type:
c:> net view

If a machine called, say, 'SATURN' is available to you, then connect in the
following way.
c:> net use k: SATURNWebSpace
c:> net use z: SATURNdforbes
The command completed successfully.
SATURN is a Windows compatible NETBIOS name for the server, which is
actually a Unix machine pretending to be a Windows server.
The 'real' name of SATURN is 'nthomes.inf.brad.ac.uk' and 'saturn.inf.brad.ac.uk'.
How can a Unix filestore 'pretend' to be a Windows filestore?
The protocols used are called SMB or 'Server Message Blocks' which are an open
standard. The information transfer using SMB looks the same on a Unix box running
a SAMBA server, as on a Windows box running FileServer.

Networking

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