Exit Zen
52
../../principles/reliability.rst:217
English
`Bit stuffing` reserves the `01111110` bit string as the frame boundary marker and ensures that there will never be six consecutive `1` symbols transmitted by the physical layer inside a frame. With bit stuffing, a frame is sent as follows. First, the sender transmits the marker, i.e. `01111110`. Then, it sends all the bits of the frame and inserts an additional bit set to `0` after each sequence of five consecutive `1` bits. This ensures that the sent frame never contains a sequence of six consecutive bits set to `1`. As a consequence, the marker pattern cannot appear inside the frame sent. The marker is also sent to mark the end of the frame. The receiver performs the opposite to decode a received frame. It first detects the beginning of the frame thanks to the `01111110` marker. Then, it processes the received bits and counts the number of consecutive bits set to `1`. If a `0` follows five consecutive bits set to `1`, this bit is removed since it was inserted by the sender. If a `1` follows five consecutive bits sets to `1`, it indicates a marker if it is followed by a bit set to `0`. The table below illustrates the application of bit stuffing to some frames.
0/11800 · 1180
52
../../principles/transport.rst:127
English
The figure below provides a representation of the connectionless service as a `time-sequence diagram`. The user on the left, having address `S`, issues a `Data.request` primitive containing Service Data Unit (SDU) `M` that must be delivered by the service provider to destination `D`. The dashed line between the two primitives indicates that the `Data.indication` primitive that is delivered to the user on the right corresponds to the `Data.request` primitive sent by the user on the left.
0/4910 · 491
53
../../bibliography.rst:323
English
Semke, J., Mahdavi, J., and Mathis, M., `Automatic TCP buffer tuning <http://doi.acm.org/10.1145/285243.285292>`_. SIGCOMM Computer Communication Review 28, 4 (Oct. 1998), 315-323.
0/1800 · 180
53
../../glossary.rst:315
English
The original file containing the list of all Internet hosts. This file has been deprecated, but Unix variants still maintain a local ``/etc/hosts`` containing mappings between names and IP addresses. See http://man7.org/linux/man-pages/man5/hosts.5.html for a description of the format of this file on Linux.
0/3080 · 308
53
../../exercises/network.rst:364
English
3 via D
0/100 · 7
53
../../principles/reliability.rst:220 • ../../principles/reliability.rst:258
English
Original frame
0/140 · 14
53
../../principles/transport.rst:146
English
There are several possible implementations of the connectionless service. Before studying these realizations, it is useful to discuss the possible characteristics of the connectionless service. A `reliable connectionless service` is a service where the service provider guarantees that all SDUs submitted in `Data.requests` by a user will eventually be delivered to their destination. Such a service would be very useful for users, but guaranteeing perfect delivery is difficult in practice. For this reason, network layers usually support an `unreliable connectionless service`.
0/5790 · 579
54
../../bibliography.rst:329
English
Stevens R. and Fenner, and Rudoff, A., `UNIX Network Programming: The sockets networking API <http://books.google.com/books?id=ptSC4LpwGA0C>`_, Addison Wesley, 2004
0/1640 · 164
54
../../glossary.rst:262
English
HTML
0/100 · 4
54
../../exercises/network.rst:365
English
C
0/100 · 1
54
../../principles/reliability.rst:220 • ../../principles/reliability.rst:258
English
Transmitted frame
0/170 · 17
54
../../principles/sharing.rst:231
English
Distributing the load across the network
0/400 · 40
54
../../principles/transport.rst:148
English
An `unreliable connectionless` service may suffer from various types of problems compared to a `reliable connectionless service`. First of all, an `unreliable connectionless service` does not guarantee the delivery of all SDUs. This can be expressed graphically by using the time-sequence diagram below.
0/3030 · 303
55
../../bibliography.rst:330
English
Sklower, K. 1989. `Improving the efficiency of the OSI checksum calculation <http://doi.acm.org/10.1145/74681.74684>`_. SIGCOMM Computer Communication Review 19, 5 (Oct. 1989), 32-43.
0/1830 · 183
55
../../glossary.rst:264
English
The HyperText Markup Language specifies the structure and the syntax of the documents that are exchanged on the world wide web. HTML is maintained by the `HTML working group <https://www.w3.org/html/wg/>`_ of the :term:`W3C`
0/2240 · 224
55
../../exercises/network.rst:365
English
1 via C
0/100 · 7
55
../../principles/network.rst:249
English
For example, consider again the network topology above. `A` sends a control packet towards `B`. The initial `record route` is empty. When `R1` receives the packet, it adds its own address to the `record route` and forwards a copy to `R2` and another to `R3`. `R2` receives the packet, adds itself to the `record route` and forwards it to `R3`. `R3` receives two copies of the packet. The first contains the `[R1,R2]` `record route` and the second `[R1]`. In the end, `B` will receive two control packets containing `[R1,R2,R3,R4]` and `[R1,R3,R4]` as `record routes`. `B` can keep these two paths or select the best one and discard the second. A popular heuristic is to select the `record route` of the first received packet as being the best one since this likely corresponds to the shortest delay path.
0/8050 · 805
55
../../principles/reliability.rst:222
English
0001001001001001001000011
0/250 · 25
55
../../principles/transport.rst:165
English
In practice, an `unreliable connectionless service` will usually deliver a large fraction of the SDUs. However, since the delivery of SDUs is not guaranteed, the user must be able to recover from the loss of any SDU.
0/2160 · 216
56
../../bibliography.rst:335
English
Stevens, R., `UNIX Network Programming, Volume 1, Second Edition: Networking APIs: Sockets and XTI <http://books.google.com/books?id=ptSC4LpwGA0C>`_, Prentice Hall, 1998
0/1690 · 169