cnp3-ebook/exercises/reliability

Exit Zen

14 ../../exercises/reliability.rst:31

	English The bandwidth of the two directions of the link is set to `B` bits per second 77/10000 · 77
15 ../../exercises/reliability.rst:32

	English The delay between the two hosts is `s` seconds in both directions 65/10000 · 65
16 ../../exercises/reliability.rst:33

	English there are no transmission errors 32/10000 · 32
17 ../../exercises/reliability.rst:35

	English Consider a go-back-n sender and a go-back receiver that are directly connected with a 10 Mbps link that has a propagation delay of 100 milliseconds. Assume that the retransmission timer is set to three seconds. If the window has a length of 4 frames, draw a time-sequence diagram showing the transmission consisting of 10 data frames (each frame contains 10000 bits): 367/10000 · 367
18 ../../exercises/reliability.rst:37

	English when there are no losses 24/10000 · 24
19 ../../exercises/reliability.rst:38

	English when the third and seventh frames are lost 42/10000 · 42
20 ../../exercises/reliability.rst:39

	English when every second acknowledgment is discarded due to transmission errors 72/10000 · 72
21 ../../exercises/reliability.rst:41

	English Same question when using selective repeat instead of go-back-n. Note that the answer is not necessarily the same. 113/10000 · 113
22 ../../exercises/reliability.rst:45

	English Practice 8/10000 · 8
23 ../../exercises/reliability.rst:47

	English Reliable protocols depend on error detection algorithms to detect transmission errors. The following questions will reinforce your understanding of these algorithms. 165/10000 · 165
24 ../../exercises/reliability.rst:49

	English Reliable protocols rely on different types of checksums to verify whether frames have been affected by transmission errors. The most frequently used checksums are : 164/10000 · 164
25 ../../exercises/reliability.rst:51

	English the Internet checksum used by UDP, TCP and other Internet protocols which is defined in :rfc:`1071` and implemented in various libraries. 137/10000 · 137
26 ../../exercises/reliability.rst:52

	English the 16 bits or the 32 bits Cyclical Redundancy Checks (CRC) that are often used on disks, in zip archives and in datalink layer protocols. See http://rosettacode.org/wiki/CRC-32 for CRC-32 implementations in various languages. 226/10000 · 226
27 ../../exercises/reliability.rst:53

	English the Fletcher checksum [Fletcher1982]_, see https://en.wikipedia.org/wiki/Fletcher%27s_checksum for implementation details. 122/10000 · 122
28 ../../exercises/reliability.rst:55

	English By using your knowledge of the Internet checksum, can you find a transmission error that will not be detected by these checksums? 129/10000 · 129
29 ../../exercises/reliability.rst:57

	English The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that are able to detect : 97/10000 · 97
30 ../../exercises/reliability.rst:59

	English all errors that affect an odd number of bits 44/10000 · 44
31 ../../exercises/reliability.rst:60

	English all errors that affect a sequence of bits which is shorter than the length of the CRC 85/10000 · 85
32 ../../exercises/reliability.rst:62

	English Implement a small software that computes the CRC-32 for a text file. Then, modify the contents of the file to change an even number of bits or an odd number of bits inside the file. When modifying the file, remember that an ASCII file is composed of 8 bits characters that are encoded by using the ASCII table that you can find at : http://en.wikipedia.org/wiki/ASCII . You can also write a small program that produces binary files that are a small variation of each other. 473/10000 · 473
33 ../../exercises/reliability.rst:64

	English Checksums and CRCs should not be confused with secure hash functions such as MD5 defined in :rfc:`1321` or SHA-1 described in :rfc:`4634`. Secure hash functions are used to ensure that files or sometimes frames/packets/segments have not been modified. Secure hash functions aim at detecting malicious changes while checksums and CRCs only detect random transmission errors. Use the `shasum <http://linux.die.net/man/1/shasum>`_ or `md5sum <http://linux.die.net/man/1/md5sum>`_ programs on Linux to perform the same tests as above. 530/10000 · 530

Shortcut	Action
`?`	Open available keyboard shortcuts.
`Alt` + `Home`	Navigate to the first translation in the current search.
`Alt` + `End`	Navigate to the last translation in the current search.
`Alt` + `PageUp` or `Ctrl` + `↑` or `Alt` + `↑` or `Cmd` + `↑` or	Navigate to the previous translation in the current search.
`Alt` + `PageDown` or `Ctrl` + `↓` or `Alt` + `↓` or `Cmd` + `↓` or	Navigate to the next translation in the current search.
`Ctrl` + `Enter` or `Cmd` + `Enter`	Submit current form; this works the same as pressing Save and continue while editing translation.
`Ctrl` + `Shift` + `Enter` or `Cmd` + `Shift` +`Enter`	Unmark translation as Needing edit and submit it.
`Alt` + `Enter` or `Option` + `Enter`	Submit the string as a suggestion; this works the same as pressing Suggest while editing translation.
`Ctrl` + `E` or `Cmd` + `E`	Focus on translation editor.
`Ctrl` + `U` or `Cmd` + `U`	Focus on comment editor.
`Ctrl` + `M` or `Cmd` + `M`	Shows Automatic suggestions tab.
`Ctrl` + `1` to `Ctrl` + `9` or `Cmd` + `1` to `Cmd` + `9`	Copies placeable of a given number from source string.
`Ctrl` + `M` followed by `1` to `9` or `Cmd` + `M` followed by `1` to `9`	Copy the machine translation of a given number to current translation.
`Ctrl` + `I` followed by `1` to `9` or `Cmd` + `I` followed by `1` to `9`	Ignore one item in the list of failing checks.
`Ctrl` + `J` or `Cmd` + `J`	Shows the Nearby strings tab.
`Ctrl` + `S` or `Cmd` + `S`	Focus on search field.
`Ctrl` + `O` or `Cmd` + `O`	Copy the source string.
`Ctrl` + `Y` or `Cmd` + `Y`	Toggle the Needs editing checkbox.
`→`	Browse the next translation string.
`←`	Browse the previous translation string.