![]() For instance, how does TCP provide flow control, how does ARP map physical addresses to IP addresses, and how does IP know where to send a datagram addressed to a different subnet? These questions are explored later in this book. Of course, there are endless details describing how each protocol goes about fulfilling its assigned tasks. The data frame is converted to a stream of bits that is transmitted over the network medium.(ARP, Address Resolution Protocol, translates IP addresses to physical addresses.) In the case of a LAN system such as ethernet, the frame may contain physical address information obtained from lookup tables maintained using the Internet layer ARP protocol. The Network Access layer creates one or more data frames designed for entry onto the physical network. The IP datagram enters the Network Access layer, where it passes to software components designed to interface with the physical network.The data segment passes to the Internet level, where the IP protocol provides logical-addressing information and encloses the data into a datagram.UDP offloads more of the error control responsibilities to the application. It is faster than TCP, but it is not as reliable. TCP is more reliable than UDP, but the additional error checking and flow control mean that TCP is slower than UDP. TCP goes to great effort to guarantee the delivery of the data. As you learn in Hour 6, “The Transport Layer,” connection-oriented protocols provide more sophisticated flow control and error control than connectionless protocols. TCP is a connection-oriented protocol.Programs can access the network through either TCP or UDP, depending on the program’s requirements: Data passes from a protocol, network service, or application programming interface (API) operating at the Application layer through a TCP or UDP port to either of the two Transport layer protocols (TCP or UDP).Of course, there are additional protocols and services in the complete package, but Figure 2.4 shows most of what is going on.įigure 2.4 A quick look at the basic TCP/IP networking system. It is sometimes useful to view these important protocols in the foreground, against the backdrop of the layering system described earlier in this hour.įigure 2.4 describes the basic TCP/IP protocol networking system. In fact, though every protocol has a role to play, most of the functionality of the TCP/IP suite can be described in terms of only a few of its most important protocols. Second, itemizing the various protocols as subheads within the greater topic of a protocol layer can give the false impression that all protocols are of equal importance. However, focusing solely on protocol layers also creates some limitations.įirst, talking about protocol layers rather than protocols introduces additional abstraction to a subject that is already excruciatingly abstract. The layering system does provide insights into the protocol system, and it’s impossible to describe TCP/IP without first introducing its layered architecture. ![]() The practice of describing protocol systems in terms of their layers is widespread and nearly universal. Learn More Buy A Quick Look at TCP/IP Networking Hence, they synchronize their "view" of time by communicating numbers.Sams Teach Yourself TCP/IP in 24 Hours, 5th Edition Then, the sender's view of time would be different from the receivers. Imagine if we didn't have a universal notion of time. So your friend asks you to resend the letter at position 3 (this is the idea behind the expected acknowledgement number).Īs mentioned in the article, it may be just that ('c', 3) is taking longer to arrive and so in that case, the sender sends a duplicate message, but duplicates are typically dropped by the receiver.Ī helpful way to think about these numbers is that they synchronize the data so both parties have the same "view" of it. It's missing 'c' because it expects a continuous increase of numbers and 3 is missing. Now, suppose the friend gets ('b', 2), but then ('d', 4). The numbers are used in case the packets/messages arrive out of order. Imagine you want to send the letters of the alphabet to a friend over the Internet.
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