| Chapter 1. Network Administration Fundamentals | ||
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| Chapter 1. Network Administration Fundamentals | ||
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Table of Contents
The course we doing now is really the Foundation for TCP/IP and Network administration, and essentially before we can network administration a box, (a Linux machine) we need to understand more about TCP/IP.
The entire Internet is based upon the TCP/IP protocol.
In fact TCP/IP was developed on Unix many years ago and was the fundamental building block when building the Linux networking environment.
TCP/IP stands for Transmission Control Protocol /Internet Protocol.
IP is broken up into two protocols:
TCP (Transfer Control Protocol)
UDP (User Datagram Protocol)
Essentially the IP protocol is the main protocol for transferring information across the Internet.
So before we explore how TCP/IP works, let have a look at the underlying structure of how it is supposed to work.
If we look at the TCP and the IP protocol, it is essentially built up of a stack, think of it as a stack of books, each representing a different layer (5 layers in all).
At the lowest level we have a physical Layer - often the physical layer will be Ethernet, fast Ethernet, gigabit Ethernet, it might be a Token Ring, Fiber Data Distributed Interface (FDDI) amongst many possibilities.
Essentially what that boils down to, is the cabling, the network cards, the switches, the routers what do they talk at a physical layer?
Are they gigabit devices, Ethernet devices or Token Ring devices?
This level would consist of the device driver and network interface card and is responsible for forming the packets and then transmitting them across the physical media.
This layer is referred to as the Media Access Control Layer, the Link Layer or Layer-2.
The MAC layer is responsible for the MAC address of a network card. This is a 12 byte address, commonly the hardware address of the interface card. The MAC address on my only interface card is: 00:01:03:8C:FB:01. Since any two machines can only talk between one another at the MAC level, they each need to know each other's MAC addresses in order to communicate.
The destination address of the packets are checked at this level when the correct destination is reached, the Ethernet header is stripped from the packet and it is passed to the Network layer of that system.
The network layer is responsible for IP addressing in the network. In fact, the network layer is critical to so many aspects of communication and it is where IP gets its name - the Internet Protocol. IP addresses denote the logical network as well as the address of each device on the network.
This layer has the capability of handling two protocols, the first is Transmission Control Protocol and the second is User Datagram Protocol (TCP and UDP).
TCP is responsible for breaking up the message into packets and reassembling the message at the other end. Resending anything that is lost and making sure that the message is put back together from the packets in the correct order.
UDP is designed for applications that do not require the packets to be in any specific order. UDP is therefore termed a connection-less protocol.
At this level the server provides the requested service for the client. For example, the client requests a login into the server, so the client requests a remote login and the server provides the service with the remote login daemon. The service that is provided is the login service.
Table 1.1. TCP/IP Protocols and some of the related services
| Layer | Services |
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| Application Layer | e.g. ftp (transfer files), telnet, smtp (simple message transfer protocol), NFS |
| Transport Layer | TCP and UDP |
| Network Layer | IP |
| MAC Layer | Network device e.g. /dev/ and MAC address |
| Physical Layer | e.g. Ethernet, Token Ring, SLIP |
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| Network Administration |  |
The OSI Model |