Device Drivers and the OSI Model
OSI model is an abstract model making it difficult to assimilate with the software and the hardware that is actually used. The article discusses network protocols and how they can be applied to the various layers of the OSI Model.
For every hardware device to work a software based device driver is required. While some drivers may be inbuilt in the system others may be required to be installed separately. The distinction gets lost with Windows Server 2008 R2 for drivers for a wide range of network cards. At the time on introduction of Windows 3.11, network drivers specified by the vendors. The vendors tried to deal with it by developing driver interfaces that could support multiple cards bound to multiple protocols. Services that correspond with the Data Link Layer are provided by network adapter cards and drivers.
Network Protocol Basics
Protocols can be defined as the manner for exchange of information that has been agreed upon by two people, computers or even appliances. In an OSI model, there are protocols at different levels and it is the protocol at a specific level that determines its functionality. Protocol stack also known as protocol suite is a term used for describing protocols that work together at one or more than one layers of the OSI model.
How Protocols Work
To put it in simple words a protocol is a series of steps that have been agreed between parties or are predefined. An example of a protocol could be a telephone conversation for it follows a scheduled protocol - Greetings, Conversation followed by a signing off. Same is the case with computers. To explain it with an example - the sending computer breaks the data into packets, adds addressing information and identifies the destination followed by delivery of data. The receiving computer follows the following steps - Acceptance of data, removal of transmitting information and reassembling of packets. Every computer needs to follow these steps and in the prescribed order.
Ethernet networks that run on IP and use TCP as the transport protocol basically send and receive data in small portions known as packets. Construction, modification and disassembly of packets is done as the data travels through the sending stack by network protocols. The smaller chunks are assembled in three parts - header, data and trailer.
Protocols and Binding
There are many protocol stacks that can perform network functions and there are a variety of network interface cards that can be installed on a machine. A machine may support more cards than one and more than one protocol stacks may be used at a point of time.
The protocol stacks are linked with the network device driver by a process known as binding. It makes it possible to have multiple protocols on a single card. A machine with multiple interface adapters can have an identical protocol bound to multiple network cards. The binding process can also be used through the entire OSI layers in order to link two protocol stacks. The device driver and the network interface card are bound; the TCP/IP and the device driver are bound.
There are two ways in which computers can be arranged:
- Using connectionless protocols: Television and Radio are two examples of connectionless protocols. These systems are based on the assumption that all the data will be transmitted. These protocols are fast. An example of a connectionless protocol is UDP - User Datagram Protocol.
- Using connection-oriented protocols: These protocols work quite the same way as a telephone. A number has to be dialed and a connection established with the other end before a message can be sent. These connections are based on the assumption that data may be lost or the arrangement may get distorted during transmission. It is these protocols that ensure that all the data gets through and reaches in its proper sequence.
For achieving this, retention of transmitted data and negotiating for transmission as and when required is done by these protocols. On receipt of all the data that is required it is reassembled into correct sequence and passed on to a higher level protocol. An example of a connection oriented protocol is TCP. Protocols other than those considered reliable cannot be said to be undependable. Protocols coming in that category do not allow retransmission of data that has been lost or has errors.
Network Protocols and Windows Server 2008 R2
There are a number of protocol stacks that are being used in the various networks the world over. Along with NetBIOS, NetWare, AppleTalk and TCP/IP, there are some additional and special protocols like Digital's (now HP/Compaq's) DECnet and IBM's Systems Network Architecture (SNA) that are available. The protocols fall in three categories Application protocols, Transport protocols and Network protocols.
Network Protocols Not Supported in Windows Server 2008 R2
Protocols like NWLink, Serial Line Interface Protocol (SLIP), AppleTalk and TCP/IP. Different protocols are supported by Windows Server 2008 R2 and support has been withdrawn for some of the technologies like Bandwidth Allocation Protocol (BAP), Serial Line interface Protocol (SLIP) and X.25. Connections that were based on SLIP were updated automatically to connections that were PPP based.
TCP/IP Preferred for Windows Server 2008 R2
Version 4 and 6 of TCP/IP networking protocols are supported by Microsoft Windows 2008 R2. These protocols are not simple and are sufficient for networks like Internet. Efforts are on by Microsoft to promote TCP/IP as a solution that is suitable for all network protocol. Active Directory is the default protocol for Windows Server 2008 R2.
TCP/IP in its actual situation is a combination of the Transmission Control Protocol and the Internet Protocols. When work began on the TCP/IP protocol, the aim was to develop a protocol that was sturdy enough to successfully route communications in an environment damaged by nuclear war. The protocol was not tested for actual goals but the design contributed towards what we know today as Internet.
IP is the most commonly used protocol used for setting up connection between computers and it is also the protocol of the internet. IP created for military networks was provided to governmental agencies and universities without any costs. Today IP is the protocol that is widely accepted for it has numerous advantages.
The main advantages of the protocol are:
- Wide connectivity amongst computers and servers of different types;
- Solid support to routing using a variety of flexible routing protocols;
- Support for name and address resolution;
- Support for a large number of Internet standard protocols;
- A network number and name assignment that is central in nature.