The DoD Schichtenmodell is a theoretical model department of the OF Defense (the US Department of Defense), after which Internet was developed. In the model the individual tasks are divided during the data communication in the Internet into layers developing one on the other. For each layer there is a set of minutes (see Internet minutes family), which solve the tasks of the respective layer in different way. 1970 of the DARPA was developed. It at that time still concerned a purely military net, which should be protected by a decentralized structure against losses.

Layers

Network ACCESS layer

In the network ACCESS layer the problem of the data communication is solved from directly connected computers. Here is of importance, which transmitting medium (copper cable, radio net, fiber-optic cable, etc.), which cable code (computer centre code, NRZ code, AMI code, etc.) and which access minutes (Ethernet, token ring, FDDI, etc.) are used. With the help of the MAC address, which contains each network map, for it one indicates, which computer is to receive the packet.

When dispatching data over several direct connection networks of rout too rout must this minutes of everyone on be built times again. The MAC address of the next network knot must be registered, to which the package is to be sent. In addition both the transmitting medium and access minutes can change.

Internet layer

The task of minutes of the Internet layer is to be made possible it a network width for addressing. , Each network map a network address is thus assigned to each computer. Differently than the MAC address this address will assign on the basis of logical criteria and made possible so that large networks beleiben managable. It is comparable with telephone numbers, belonged to which preselection prevents and thus that a switching plant must know all telephone numbers of the world. Thus it is possible packets of routs too routs over several you hitting a corner connecting networks to the goal host to send. Meistverbreitetes minutes of this layer is Internet minutes.

Host ton host layer

The task of minutes of the host ton host layer is it the transport of the data between two processes on the different computers to make possible (end end connection). That is there it is not necessarily, sufficient the data to the target computer to transport, but it must be also indicated, which of the programs running there, which wait for data of the net, which is to receive respective package. There are here different beginnings of the information transfer:

• During a connectingless transmission, no control is inserted in this layer that the package also arrives. Control must take place in the Process layer. Is comparable with the dispatching of a letter in the material world.
• To a confirmed connectingless transmission a confirmation message is to be announced to the transmitter intended around the receipt of the package. It corresponds to sending a writing with return ticket.
• During an connectingoriented transmission before the transmission a logical connection is developed and kept upright. Even if no data will transfer, control information is exchanged between the computer. This procedure makes control and data flow control for the package sequence possible.

In the Internet for it two minutes TCP and UDP are available. With TCP minutes it concerns connectingoriented minutes. It makes one reliably for transmission possible of the data. This however also a multiplicity at additional information, transferring become meant beside the actual message. UDP minutes against it are connectingless minutes. Kept by the smaller administration expense will the network load with this minutes smaller and it can a higher information flow-rate be achieved.

Process layer

In the Process layer minutes are certain applications are meant. They contain the actual information, which will transfer are.

Structure of package

Each level of the layer model adds information when dispatching the data as package headers, which are evaluated with the receiver on the same level. One can imagine that like an envelope, in which an envelope, in which an envelope, in which a letter is. On each envelope thereby the information which is needed in the respective layer, stands:

 {|border= " 1 " cellspacing= " 0 " cellpadding= " 5 " style= " border collapse: collapse; "“| bgcolor= " #CCCCCC"” | {| cellspacing= " 0"” | bgcolor= " #CCCCCC"” | data of the Internet layer | {|border= " 1"” cellspacing= " 0"” cellpadding= " 5"” style= " border collapse: collapse; "” | bgcolor= " #DDDDDD " | {| cellspacing= " 0 " | bgcolor= " #DDDDDD " | data of the host ton host layer | {|border= " 1 " cellspacing= " 0 " cellpadding= " 5 " style= " border collapse: collapse; "“| |Daten bgcolor= " #EEEEEE"” the Process layer |} |} |} |} |} 

The OSI Schichtenmodell

Some years according to the DoD model the OSI model was developed by the ISO. The structure is similarly distributed to the DoD model however on seven instead of only on four layers. Although the DoD model had in practice proven its fitness considered the large computer companies using the OSI model for their own transmission protocols. Since 1988 even the US Government supported the new model. Nevertheless minutes of the DoD model became generally accepted finally. Nowadays TCP/IP minutes are usually-used minutes in the Internet. To frequently still describe nevertheless the OSI model in addition used around expirations of communication.

Articles in category "DoD Schichtenmodell"

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