냐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� +-+-+-+-+-+-+-+-+ 栢栢栢栢昉께께굇굇굅같�|O|u|t|b|r|e|a|k|臍같굇굇굉께께栢栢栢� +-+-+-+-+-+-+-+-+ Issue #4 - Page 1 of 12 냐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 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, that뭩 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 멺oodies� 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