cnp3-ebook/protocols/transport-service

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1 ../../protocols/transport-service.rst:6

	English The application layer 21/10000 · 21
2 ../../protocols/transport-service.rst:8

	English Networked applications rely on the transport service. As explained earlier, there are two main types of transport services : 124/10000 · 124
3 ../../protocols/transport-service.rst:10

	English the `connectionless` service 28/10000 · 28
4 ../../protocols/transport-service.rst:11

	English the `connection-oriented` or `byte-stream` service 50/10000 · 50
5 ../../protocols/transport-service.rst:13

	English The connectionless service allows applications to easily exchange messages or Service Data Units. On the Internet, this service is provided by the UDP protocol that will be explained in the next chapter. The connectionless transport service on the Internet is unreliable, but is able to detect transmission errors. This implies that an application will not receive data that has been corrupted due to transmission errors. 421/10000 · 421
6 ../../protocols/transport-service.rst:15

	English The connectionless transport service allows networked application to exchange messages. Several networked applications may be running at the same time on a single host. Each of these applications must be able to exchange SDUs with remote applications. To enable these exchanges of SDUs, each networked application running on a host is identified by the following information : 376/10000 · 376
7 ../../protocols/transport-service.rst:17

	English the `host` on which the application is running 46/10000 · 46
8 ../../protocols/transport-service.rst:18

	English the `port number` on which the application `listens` for SDUs 61/10000 · 61
9 ../../protocols/transport-service.rst:20

	English On the Internet, the `port number` is an integer and the `host` is identified by its network address. There are two types of Internet addresses : 145/10000 · 145
10 ../../protocols/transport-service.rst:22

	English `IP version 4` addresses that are 32 bits wide 46/10000 · 46
11 ../../protocols/transport-service.rst:23

	English `IP version 6` addresses that are 128 bits wide 47/10000 · 47
12 ../../protocols/transport-service.rst:25

	English IPv4 addresses are usually represented by using a dotted decimal representation where each decimal number corresponds to one byte of the address, e.g. `203.0.113.56`. IPv6 addresses are usually represented as a set of hexadecimal numbers separated by semicolons, e.g. `2001:db8:3080:2:217:f2ff:fed6:65c0`. Today, most Internet hosts have one IPv4 address. A small fraction of them also have an IPv6 address. In the future, we can expect that more and more hosts will have IPv6 addresses and that some of them will not have an IPv4 address anymore. A host that only has an IPv4 address cannot communicate with a host having only an IPv6 address. The figure below illustrates two applications that are using the datagram service provided by UDP on hosts that are using IPv4 addresses. 782/10000 · 782
13 ../../protocols/transport-service.rst:47

	English Textual representation of IPv6 addresses 40/10000 · 40
14 ../../protocols/transport-service.rst:49

	English It is sometimes necessary to write IPv6 addresses in text format, e.g. when manually configuring addresses or for documentation purposes. The preferred format for writing IPv6 addresses is `x:x:x:x:x:x:x:x`, where the `x` 's are hexadecimal digits representing the eight 16-bit parts of the address. Here are a few examples of IPv6 addresses : 343/10000 · 343
15 ../../protocols/transport-service.rst:51

	English `abcd:ef01:2345:6789:abcd:ef01:2345:6789` 41/10000 · 41
16 ../../protocols/transport-service.rst:52

	English `2001:db8:0:0:8:800:200c:417a` 30/10000 · 30
17 ../../protocols/transport-service.rst:53

	English `fe80:0:0:0:219:e3ff:fed7:1204` 31/10000 · 31
18 ../../protocols/transport-service.rst:56

	English IPv6 addresses often contain a long sequence of bits set to `0`. In this case, a compact notation has been defined. With this notation, `::` is used to indicate one or more groups of 16 bits blocks containing only bits set to `0`. For example, 243/10000 · 243
19 ../../protocols/transport-service.rst:58

	English `2001:db8:0:0:8:800:200c:417a` is represented as `2001:db8::8:800:200c:417a` 77/10000 · 77
20 ../../protocols/transport-service.rst:59

	English `ff01:0:0:0:0:0:0:101` is represented as `ff01::101` 54/10000 · 54

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