1. Translate the following words and phrases:
modularity to integrate
suit constituent
layering approach to constitute
application layer to evolve
host-to-host layer to recognize
internet layer to implement
network access layer to handle
character translation to include
underlying protocol to assume
generated traffic to log
U DP identity
TCP
2. Look through the text and find English equivalents for the following:
1. набор коммуникационных признаков;
2. разбить задачу на;
3. участок кода (программы);
4. коммуникационная задача;
5. уровневый набор коммуникационных протоколов;
6. процессы, представляющие приложения;
7. процессы, представляющие компьютерные сети;
8. процессы, представляющие узлы сети;
9. доступ к среде передачи;
10. процесс, представляющий средства физической доставки данных;
11. взаимодействующие приложения;
12. взаимодействие;
13. примеры протоколов, поддерживаемых на прикладном уровне;
14. достоверность передаваемых данных;
15. приложения, выполняемые на компьютерной сети;
16. целостность данных;
17. на обоих концах соединения;
18. открытым образом помечая пакеты;
19. природа взаимодействующих приложений.
3. Translate the questions and answer them.
1. Каков был выбор у разработчиков при постановке задачи по коммуникационным протоколам?
2. Понимание чего легло в основу создания модели архитектуры TCP/IP коммуникаций?
3. Какова иерархия элементов данной модели?
4. За что отвечает уровень процессов, представляющих приложения?
5. За что отвечает уровень процессов, представляющие компьютерные сети?
6. Что включает в себя протоколы, работающие в транспортном уровне?
4. Read and translate the continuation of the text.
Internet Layer
The internet layer is responsible for determining the best route that data packets should follow to reach their destination. If the destination host is attached to the same network, data is delivered directly to that host by the network access layer; otherwise, if the host belongs to some other network, the internet layer employs a routing process for discovering the route to that host. Once the route is discovered, data is delivered through intermediate devices, called routers, to its destination. Routers are special devices with connections to two or more networks. Every router contains an implementation of TCP/IP up to and including the internet layer.
As shown in Figure 3, hosts alto and tenor belong to different networks. The intervening networks are connected via devices called routers. For host alto to deliver data to host tenor, it has to send its data to router Rl first. Router Rl delivers to R2. and so on until the data packet makes it to host tenor. The "passing-the-buck" process is known as routing and is responsible for delivering data to its ultimate destination. Each of the involved routers is responsible for assisting in the delivery process, including identifying the next router to deliver to in the direction of the desired destination. The protocols that operate at the internet layer include IP (Internet Protocol), and RIP (Route Information Protocol) among others.
Network Access Layer
The network access layer is where media access and transmission mechanisms take place. At this layer, both the hardware and the software drivers are implemented. The protocols at this layer provide the means for the system to deliver data to other devices on a directly attached network. This is the only layer that is aware of the physical characteristics of the underlying network, including rules of access, data frame (name of a unit of data at this layer) structure, and addressing.
While the network access layer is equipped with the means, for delivering data to devices on a directly attached network, it does so based on directions from IP at the internet layer. To understand the implications of this statement, look at the internetwork of Figure 3. Hosts jade and alto are said to belong to the same network since they are directly attached to the same physical wire. In contrast, host tenor belongs to a different network.
When a requirement arises to deliver data out of host alto, the internet layer (in particular the IP protocol) has to determine whether the destined host is directly attached to the same network. If so, IP passes the data packet to the network access layer and instructs it to deliver the data to the designated host. So, should, for example, the packet be destined to host jade. IP instructs the network access layer to take the necessary steps to deliver it to that host.
However, if IP on host alto is required to deliver the data packet to a host on a different network (for instance, host tenor), IP has to determine to which network the host belongs and how to get the packet there. As can be seen from the diagram, to deliver packets to host tenor, IP in host alto has to send the packet first to router Rl, then Rl in turn has to forward it to R2 (or R3), and so on, as explained in the previous subsection. Consequently, IP passes the packet on to the network access layer and instructs it to deliver the packet to router Rl. Notice how in both cases, the case of a host directly attached to same network (host jade) and the case of a host on different network (host tenor), the network access layer followed the addressing instructions imposed by IP at the internet layer. In other words, the network access layer relies on IP at the layer above it to know where to send the data.