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                             Issue #4 - Page 1 of 12 
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Hello folks this is TCP/IP part 3 by antimatt3r. ENJOY!

Client / server is defined by software, not hardware. The client application 
on one computer requests services from a computer running server software. 
Client / server software can run on any hardware.

   Server computers have a recource it shares with other computers, or a 
service it can perform on behalf of other computers and users.  A web server 
sends files and images to a web browser (client). A web server on a private 
intranet is an internal information server. A commerce server lets you 
conduct buisness over the web. The server software includes security 
features such as Secure Socket Layer (SSL). A file server shares its disk 
space with other computers, when there are multiple operating systems; there 
are various file formats. The server hides those format differences from the 
clients. Software converts the format. This is called "transparent file 
access." A compute server is a computer that will run a program for you.

   Client is a computer that borrows a service or recource from another 
computer. A thin client is the smallest, lightest, and least expensive 
configuration of hardware and software configured to perform the exact tasks 
you need, nothing more, nothing else. Thin client means fat server. A 
browser recieves information from a web server. Some smart cell phones are 
thin clients and have a microbrowser that knows how to display information 
on the phone screen.

   Most computers in a peer to peer network act as both clients and servers 
simultaneously. When browsing the web the browser (client) pulls information 
down from the server. Server push technology is just the opposite - the 
server initiaites the information delivery to the client. Delivery of E-mail 
is the most common push technology solution. Nowadays, content that is 
pushed is streaming audio and video.

The United States has 6 network access points.
New York - Operated by Pacific Bell
Bohemiany - Operated by ICS
Chicago -  Operated by Ameritech
San Hose and MAE West - Operated by Worldcom
San Francisco - Operated by Pacific Bell

For maps of backbones visit http://www.nthelp.com/maps.htm

An intranet is a private network within an organization or department, a 
private version on the Internet. Extranets are multiple interconnected 
intranets and internets. For example, a university in the East may want to 
share information with a university in the West; they hook together with an 
extranet.

   So who is in charge of all of this you wonder? They say that no one 
controls TCP/IP but there are several organizations that influence TCP/IP 
and its direction, as well as Internet policies:

InterNIC: Internet Network Information Center keeps lists or domains
IANA: Internet Assigned Numbers Authority is the central control for 
Internet addresses, domain names, and other protocol details. IANA maintains 
a database of top level domains, for all countries.
ICANN: Internet Corporation for Assigned Names and Numbers Association was 
incorporated in late 1990s, is taking the IANAs job over.
IAB: Internet Activities Board defines architecture for the Internet 
backbone and all the networks that link to the backbone. The IAB oversees 
TCP/IP. They have a committee that works together to solve problems with 
Internet growth problems. They work with all the following committees to set 
the direction for research and the development of the Internet.
IETF: Internet Engineering Task Force is responsible for keeping the 
Internet running. 70 groups make up the IETF. The groups develop standards 
for TCP/IP. They manage the growth and change of TCP/IP and the Internet.
IESG: Internet Engineering Steering Group sets the stretegic goals for the 
Internet. IAB appoints the chairperson and members. The IETF makes makes 
recommendations to the IESG about standardizing TCP/IP protocol for the 
Internet. The IESG manages how a protocol becomes an Internet standard. IESG 
oversees the IETF.
IRTF: Internet Research Task Force manages research into protocols. The IETF 
moves the IRTFs research into the practical world of TCP/IP and the 
Internet.
ISOC: IAB, IETF and  IRTF are part of ISOC which guides the future of the 
Internet, members are people, companies, international and government 
organizations.
W3C: World Wide Web Consortium. The W3C decides on which standards to adopt 
for the Web and its protocols.

	The Internet is close to reaching the limits of its current address 
numbering system. Although estimates vary, the average figure for when we 
will run out of addresses is around 2010, thats not too far away.

	If the Internet is close to running out of addresses, that does not mean 
that soon it wont be able to accept new companies and individuals. The IESG 
created a task force to determine how to best enhance TCP/IP to cope with 
this problem. IPv6 to the rescue.

	IPv6 is the next generation of IP, it offers millions and millions more of 
Internet addresses than we have now. Software vendors must develop products 
to cope with and understand the new addressing scheme. Some products are 
already in place. IPv6 also has some other goodies besides making 
addresses more abundant, like making it easier to assign addresses, 
increased cryptologic capabilities and advanced support for mobile devices.

	The current version of IP is IPv4. IPv5 was a research version that never 
made it to production.

	 In order for IPv6 to provide more addresses, it needs to change the 
addressing format. It works like an area code to phone numbers. The Ipv6 
task force mandates that old style IP addresses and new Ipv6 addresses must 
coexist. The transition from version 4 to version 6 will be slow and 
gradual, over the next few years. We can also be sure that the Internet will 
understand both forms of IP addresses for years to come. Read RFC 1883 for 
additional information on IPv6.

	ISO: International Standards Organization specifies worldwide standards for 
different types of computing, sets standards for networking, database, and 
charachter sets, among other things.

	OSI: Open Systems Interconnect defines network architecture and a full set 
of protocols

	OSIs interoperability standards have been designed to allow all parts of 
your network to work together. OSI divides network functions, (for example 
getting connected or sending mail), into layers and specifies how those 
layers interact.

	The ISO OSI seven layer stack:
Each layer provides services to the layer above it. In other words, each 
layer depends on the layer beneath it. When 2 peer computers are 
communicating, each PC has its own set of layers. When you send a message to 
another computer on the network, its starts at the top of the stack on youre 
computer, travels down and jumps to the other computer. When the information 
gets to the other computer it starts at the bottom layer and works its way 
up the stack to the top, application layer. LOWer layers are hardware 
orientated, HIGHer layers do thing such as email, and file transfers and are 
software related.

Layer 1 - The Physical Layer: This is the bottom of the stack, purely 
hardware, including the connection medium and the NIC.
Layer 2 - The Data Link Layer: Hardware involved, splits data into packets 
to be sent. When the information gets on the wire, the data link layer 
handles any interference.
Layer 3 - The Network Layer: Bottom layers are about hardware, TCP/IP is 
software. The network layer is the first place on the OSI model where a 
TCP/IP protocol fits in. IP works at this layer. This layer gets data from 
the data link layer (2) and sends it to the correct network address. If 
there is more than one possible path, network layer figures the best and 
fastest. Information would not get to the right place without this layer.
Layer 4 - The Transport Layer: The network layer takes your information to 
its destination, but cant guarentee that it will arrive in order or not pick 
up errors along the way. This is the transport layers job. TCP and UDP are 
both at work here. Transport makes sure that all data arrives in order and 
is error free. Without this, you couldent tusrt ouyr 
neowtkr..............get it?
Layer 5 - The Session Layer: This layer establishes and cordinates a 
session, the connection. After the session is established, security is 
turned on.
Layer 6 - The Presentation Layer: Works with filesystem and operating 
system. Files get converted from one type to another, if the server & client 
use different formats. Without this, the file transfer would be limited to 
computers of the same file format
Layer 7 - The Application Layer: This is the top layer where you do your 
work such as sending E-mail or requesting to transfer a file across the 
network. Without this layer, there is no way to create data to send, no 
browsers, and your computer wouldent know what to do with information that 
is sent to you.

	TCP/IP's 5th layer is very rich, it combines functions session, 
presentation, and application all in one layer. The third layer is the 
internet layer, this is the same as OSI's network layer. The following is 
the TCP/IP stack.

	-Application (RPC, SNMP, FTP, TFTP, DNS, DHCP, NFS, Telnet)
	-Transport  (TCP, UDP)
	-Internet  (IP, IPv6, ICMP, ARP, RARP)
	-Data link
	-Physical

	TCP/IP's modular, layered design makes it easy to innovate and add new 
componets. If you envision a new network service, as you go about designing 
the server and client applications you can simultaneously design a new 
protocol to ass to the TCP/IP suite. The protocol enables the server 
application to offer the service and lets the client application comsume 
that service. This simplicity is a key advantage of TCP/IP.

	In the fabric of a network, you find a protocol/application/service 
relationship so tightly woven together that it may be difficult to 
distinguish the threads in the cloth. We shall use FTP as an example of 
this. FTP stands for file transfer protocol, but its not only a protocol, 
its also a service and an application. (dont worry about FTP if you dont 
know what it is)(then again if you dont, bin this text) FTP is  service for 
copying files; pull or push to a remote computer. Pull is a geek term for 
download, push means upload. FTP is also an application for copying files. 
You run client applications such as browsers to get files or upload, called 
FTPD, FTP daemon. FTP is a protocol because client and server use it for 
communication to ensure the information is bit for bit identical to the 
original. Without application, a computer dosent know what to copy. Without 
service, there is no connection to the remote computer, and without the 
protocol computers cant communicate.

to be continued in the next issue (as usual)  shoutz to #hackerzlair and all 
of our outstanding outbreak krew

