So.

A Question.

What is the relationship between

Windows drive letters and

Internet web site URLs?

There is none.

There is no relationship.

Drive letters have nothing to do with the

Internet.

Absolutely nothing.

Internet file naming rules are

UNIX

URLs

• All URLs address filespace on a web server. • All URLs obey Unix filenaming rules.

• All Windows web servers obey Unix filenaming rules. • There are no exceptions at all.

• All URLs that use Windows filenames have to be 'repaired' using URL encoding before they work on the Internet.

'What are those "%20" codes in URLs?'http://www.blooberry.com/indexdot/html/topics/urlencoding.htm

"...Only alphanumerics [0-9a-zA-Z], the special characters "$-_.+!*'()," [not including the quotes], and reserved characters used for their reserved purposes may be used unencoded

within a URL."

http://www.w3schools.com/html/html_ref_urlencode.aspSpaces are converted into plus (+) signs or %20 to avoid semantic ambiguities.

Special characters or 8-bit values are converted into their hexadecimal equivalents and prefaced with a percent sign (%).

File Permissions and file access.

In DOS systems, files listed in Windows Explorer, File Manager (or equivalent) have letters next to them to indicate their permission status.

a - archive filesh - hidden filesr - read only filess - system files

Unix files and permissionsUNIX Files | Windows files-------------------------|----------------------------256 characters filename | 256 character filenamefilename.ext.ext.ext | 3 character extensionsensitive to case | not sensitive to casesecure file permissions | no effective file security

drwx------ 2 dforbes EL 512 Dec 1 17:25 Maildrwx------ 2 dforbes EL 512 Sep 2 1996 News-rw-r--r-- 1 dforbes EL 7127 Nov 28 18:38 boot.txtdrwxr-x--- 3 dforbes EL 512 Sep 2 1996 dhfdrwxr-xr-x 7 dforbes EL 512 Sep 8 14:03 frames-rw-r--r-- 1 dforbes EL 28774 Dec 1 14:08 hardware.txt-rw-r--r-- 1 dforbes EL 3144 Nov 28 18:38 memory.txt-rw-r--r-- 1 dforbes EL 15483 Nov 28 18:38 networks.txt-rw-r--r-- 1 dforbes EL 53089 Nov 27 13:56 ports.htmldrwx------ 9 dforbes EL 512 Oct 29 14:03 ugf-rw-r--r-- 1 dforbes EL 5773 Nov 27 13:56 video.htm-rw-r--r-- 1 dforbes EL 14762 Nov 27 13:56 work1.htm/homedir/dforbes%

Unix permissions determine which files can be altered, read or executed.

The permissions used are:

r - read access grantedw - write access grantedx - execute access granted

UNIX file listings have a set of 10 spaces where the letters r, w or x are written to indicate WHO is allowed to read, write, or execute that file.

- - - - - - - - - -

● The first space of the 10 may be left blank to indicate a file, or a "d" used to indicate a directory, or “l” for a 'link'.

● The remaining 9 spaces are divided into three groups of three.

A file which allows:

● read, write and execute permission to the owner, ● read and execute to a group and ● read only to everybody else,

would look like this:

d r w x r - x r - -

In each group of 3 spaces, ● the first character determines the read permission, ● the second the write permission, and ● the third the execute permission.

So ::

● The first letter group refers to the permissions granted to the owner of the file.

● The second, to a specific group of users who are granted access rights to the file.

● The third letter group determines the access rights of anybody else to the file.

These attributes can be changed by the owner of the file who decides which users can have particular access.

chmodTo change the permission set up, the chmod command is used:Each group of three permissions can be represented by an octal number (0 to 7), (1 = set permission)

d r w x r - x r - -Binary : 1 1 1 1 0 1 1 0 0Octal : 4 + 2 + 1 4 + 0 + 1 4 + 0 + 0 = 7 5 4

Command used is: chmod 754 filename. ** Only the owner of the file can change these settings.

Other commands include:● chgrp - for changing the group given access to the file● chown - to change the owner of the file

Networkinghttp://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 Windows XP for a simple peer-to-peer system. Alternatives include Novell Netware, Microsoft Windows Server 2007 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 (for comms to 100Mb/s RJ45)||____||| __ || / \ ||| O || ---BNC connection (for comms to 10Mb/s - old)| \__/ |+------+

+======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 | +-----------+

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 protocolhttp://en.wikipedia.org/wiki/Ethernet

OSILayer

AppleComputer

BanyanSystems

DECDECnet

IBMSNA

MicrosoftNetworking

NovellNetWare

TCP/IPInternet

XeroxXNS

OSIProtocols

ApplicationLayer 7

Application Programs and Protocolsfor file transfer, electronic mail, etc.

PresentationLayer 6

AppleTalkFilingProtocol(AFP)

RemoteProceduralCalls(Net RPC)

NetworkManagementNetworkApplication

TransactionServicesPresentationServices

ServerMessageBlock(SMB)

NetWareCoreProtocols(NCP

(Telnet, FTP,SMTP, etc.)

Control andProcessInteraction

ISO8823

SessionLayer 5

AppleTalkSessionProtocol(ASP)

SessionDataFlowControl

Network BasicInput/OutputSystem(NetBIOS)

Network BasicInput/OutputSystem(NetBIOS)

ISO8327

TransportLayer 4

AppleTalkTransactionProtocol(ATP)

VINESInterProcessCommunications(VIPC)

EndCommunications

TransmissionControl

NetworkBasic ExtendedUser Interface(NetBEUI)

SequencedPacketExchange(SPX)

TransmissionControl Protocol (TCP), (UDP)

SequencedPacketProtocol(SPP)

ISO8073TP0-4

Network Layer 3

DatagramDeliveryProtocol(DDP)

VINESInternetProtocol(VIP)

Routing PathControl

InternetPacketExchange(IPX)

InternetProtocol(IP)

InternetDatagramProtocol(IDP)

ISO8473(CLNP)

Data LinkLayer 2

Network Interface Cards: Ethernet, Token-Ring, ARCNET, StarLAN, LocalTalk, FDDI, ATM, etc.NIC Drivers: Open Datalink Interface (ODI), Network Independent Interface Specification (NDIS)

PhysicalLayer 1

Transmission Media:Twisted Pair, Coax, Fiber Optic, Wireless Media, etc.

http://www.lex-con.com/ http://freeside.dnsalias.org/csclass/networking/osimodel.html

IP Protocol Suite