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Reliable protocols rely on different types of checksums to verify whether frames have been affected by transmission errors. The most frequently used checksums are :
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English French Actions
a Cyclic Redundancy Check (`CRC`) un contrôle de redondance cyclique (`CRC`)
Derive a mathematical expression that provides the `goodput`, i.e. the amount of payload bytes that have been transmitted during a period of time, achieved by the Alternating Bit Protocol assuming that : Obtenez une expression mathématique pour le `goodput`, c'est-à-dire la quantité de bytes pouvant être transmis pendant une période de temps donnée, issu du protocole du bit alterné en considérant que :
Each frame contains `D` bytes of data and `c` bytes of control information Chaque frame contient `D` bytes de donnée et `c` bytes d'information de contrôle
Each acknowledgment contains `c` bytes of control information Chaque acknowledgment contient `c` bytes de information de contrôle
The bandwidth of the two directions of the link is set to `B` bits per second La bande passante dans les deux directions du câble est de `B` bits par seconde
The delay between the two hosts is `s` seconds in both directions Le délai entre deux hôtes est de `s` secondes dans les deux sens
there are no transmission errors il n'y a pas d'erreur de transmission
when there are no losses dans le cas où il n'y a pas de pertes
when every second acknowledgment is discarded due to transmission errors lorsqu'un acknowledgment sur deux est ignoré à cause des erreurs de transmission
Same question when using selective repeat instead of go-back-n. Note that the answer is not necessarily the same. Même question en utilisant du selective repeat à la place du go-back-n. Remarquez que la réponse n'est pas nécessairement la même.
Practice Exercices
Reliable protocols depend on error detection algorithms to detect transmission errors. The following questions will reinforce your understanding of these algorithms. Les protocoles fiables dépendent d'algorithmes de détection des erreurs de transmission. Les questions suivantes vont vous permettre d'approfondir votre compréhension de ces algorithmes.
Reliable protocols rely on different types of checksums to verify whether frames have been affected by transmission errors. The most frequently used checksums are : Les protocoles fiables reposent sur différents types de checksums afin de vérifier si des erreurs de transmission ont affecté les frames. Les checksums les plus fréquemment utilisés sont :
the Internet checksum used by UDP, TCP and other Internet protocols which is defined in :rfc:`1071` and implemented in various libraries.
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.
The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that are able to detect : Les contrôles de redondance cyclique (CRC) sont des outils efficaces de détection d'erreurs pouvant détecter :
all errors that affect an odd number of bits toutes les erreurs affectant un nombre impair de bits
all errors that affect a sequence of bits which is shorter than the length of the CRC toutes les errors affectant une séquence de bits plus courte que la longueur du CRC
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.
Discussion questions Questions de discussion
Consider two high-end servers connected back-to-back by using a 10 Gbps interface. If the delay between the two servers is one millisecond, what is the throughput that can be achieved by a reliable protocol that is using 10,000 bits frames and a window of
one frame une frame
ten frames dix frames
hundred frames cent frames
Is it possible for a go-back-n receiver to inter-operate with a selective-repeat sender ? Justify your answer. Est-il possible pour un récepteur go-back-n de fonctionner avec un émetteur selective-repeat ? Justifiez.

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cnp3-ebook / exercises/reliability — French

Reliable protocols rely on different types of checksums to verify whether frames have been affected by transmission errors. The most frequently used checksums are :
Les protocoles fiables reposent sur différents types de checksums afin de vérifier si des erreurs de transmission ont affecté les frames. Les checksums les plus fréquemment utilisés sont :
3 years ago
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Source string location
../../exercises/reliability.rst:54
String age
5 years ago
Source string age
5 years ago
Translation file
locale/fr/LC_MESSAGES/exercises/reliability.po, string 24