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Reliable transfer
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Reliable transfer Transfert fiable
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Transmission links have sometimes different upstream and downstream bandwidths. A typical example are access networks that use ADSL (Asymmetric Digital Subscriber Lines). Consider two hosts connected via an ADSL link having an upstream bandwidth of 1 Mbps and a downstream bandwidth of 50 Mbps. The propagation delay between the two hosts is 10 milliseconds. What is the maximum throughput, expressed in frames/second, that the alternating bit protocol can obtain on this link if each data frame has a length of 125 bytes and acknowledgments are 25 bytes long. Same question if the protocol is modified to support 1500 bytes long data frames.
How would you set the duration of the retransmission timer in the alternating bit protocol ? Comment fixeriez-vous le délai du timer de retransmission dans le protocole du bit alterné ?
A version of the Alternating Bit Protocol supporting variable length frames uses a header that contains the following fields : Une version du protocole du bit alterné à frame de longueur variable utilise une entête qui contient les champs suivants :
a `number` (0 or 1) un `nombre` (0 ou 1)
a `length` field that indicates the length of the data un champ `length` (taille) qui indique la taille des données
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

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cnp3-ebook / exercises/reliability — French

Reliable transfer
Transfert fiable
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cnp3-ebook / exercises/reliability — French

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String information

Source string location
../../exercises/reliability.rst:7
String age
5 years ago
Source string age
5 years ago
Translation file
locale/fr/LC_MESSAGES/exercises/reliability.po, string 1