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../../protocols/bgp.rst:125
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`NOTIFICATION` : this message is used to terminate a BGP session, usually because an error has been detected by the BGP peer. A router that sends or receives a `NOTIFICATION` message immediately shutdowns the corresponding BGP session.
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../../protocols/congestion.rst:201
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:math:`area=(\frac{W}{2})^2 + \frac{1}{2} \times (\frac{W}{2})^2 = \frac{3 \times W^2}{8}`
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../../protocols/email.rst:186
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The email message below, copied from :rfc:`2046` shows a MIME message containing two parts that are both in plain text and encoded using the ASCII character set. The string `simple boundary` is defined in the `Content-Type:` header as the marker for the boundary between two successive parts. Another example of MIME messages may be found in :rfc:`2046`.
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../../protocols/ethernet.rst:176
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100Base-FX
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../../protocols/http.rst:158
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the `Content-Length:` header is the :term:`MIME` header that indicates the length of the MIME document in bytes.
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../../protocols/http2.rst:260
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Finally, the client and the server need to confirm the utilization of HTTP/2.0. A client confirms this by sending the following Magic string `PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n` or `0x505249202a20485454502f322e300d0a0d0a534d0d0a0d0a` in hex. This string is followed by a SETTINGS frame. The server must send a possibly empty SETTINGS frame.
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../../protocols/ipv6.rst:128
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``2001:0db8:0:cd30::`` / ``60``
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../../protocols/ethernet.rst:156
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A hierarchical Ethernet network composed of hubs
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../../protocols/routing.rst:130
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A first solution to support such a LAN with a link-state routing protocol would be to consider that a LAN is equivalent to a full-mesh of point-to-point links as if each router can directly reach any other router on the LAN. However, this approach has two important drawbacks :
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../../protocols/rpc.rst:131
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If the `sum` method is not implemented on the server, it would reply with the following response.
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../../protocols/ssh.rst:295
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Footnotes
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../../protocols/tcp.rst:120 • ../../protocols/tcp.rst:126
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the `ACK` flag set
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../../protocols/tls.rst:162
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`Compression algorithm` : the client may propose the utilization of a specific compression algorithm (e.g. zlib). In theory, compressing the data before encrypting it is an intelligent way to reduce the amount of data exchanged. Unfortunately, its implementation in TLS has caused several security problems [PHG2013]_. For this reason, compression is usually disabled in TLS :rfc:`7525`.
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../../protocols/wifi.rst:93
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802.11 devices exchange variable length frames, which have a slightly different structure than the simple frame format used in Ethernet LANs. We review the key parts of the 802.11 frames. Additional details may be found in [IEEE802.11]_ and [Gast2002]_ . An 802.11 frame contains a fixed length header, a variable length payload that may contain up 2324 bytes of user data and a 32 bits CRC. Although the payload can contain up to 2324 bytes, most 802.11 deployments use a maximum payload size of 1500 bytes as they are used in `infrastructure` networks attached to Ethernet LANs. An 802.11 data frame is shown below.
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../../bibliography.rst:121
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McKeown N, Anderson T, Balakrishnan H, Parulkar G, Peterson L, Rexford J, Shenker S, Turner J., `OpenFlow: enabling innovation in campus networks <https://doi.org/10.1145/1355734.1355746>`_. ACM SIGCOMM Computer Communication Review. 2008 Mar 31;38(2):69-74.
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../../glossary.rst:161
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The Enhanced Interior Gateway Routing Protocol (EIGRP) is a proprietary intradomain routing protocol that is often used in enterprise networks. EIGRP uses the DUAL algorithm described in [Garcia1993]_.
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../../exercises/ex-sharing.rst:645
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Like ALOHA, CSMA relies on acknowledgments to detect where a frame has been correctly received. When a host senses an idle channel, if should transmit its frame immediately. How should it react if it detects that another host is already transmitting ? Consider two options :
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../../principles/network.rst:140
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Some networks use the arrival of packets as the trigger to compute the corresponding entries in the forwarding tables. Several technologies have been built upon this principle. When a packet arrives, the router consults its forwarding table to find a path towards the destination. If the destination is present in the forwarding table, the packet is forwarded. Otherwise, the router needs to find a way to forward the packet and update its forwarding table.
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../../principles/transport.rst:84
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The example above defines several terminals and two commands : `usercommand` and `passwordcommand`. The `ALPHA` terminal contains all letters in upper and lower case. In the `ALPHA` rule, `%x41` corresponds to ASCII character code 41 in hexadecimal, i.e. capital `A`. The `CR` and `LF` terminals correspond to the carriage return and linefeed control characters. The `CRLF` rule concatenates these two terminals to match the standard end of line termination. The `DIGIT` terminal contains all digits. The `SP` terminal corresponds to the white space characters. The `usercommand` is composed of two strings separated by white space. In the ABNF rules that define the messages used by Internet applications, the commands are case-insensitive. The rule `"user"` corresponds to all possible cases of the letters that compose the word between brackets, e.g. `user`, `uSeR`, `USER`, `usER`, ... A `username` contains at least one letter and up to 8 letters. User names are case-sensitive as they are not defined as a string between brackets. The `password` rule indicates that a password starts with a letter and can contain any number of letters or digits. The white space and the control characters cannot appear in a `password` defined by the above rule.
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../../principles/sharing.rst:175
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When the network load is low, buffer occupancy and link utilization are low. The buffers on the network nodes are mainly used to absorb very short bursts of packets, but on average the traffic demand is lower than the network capacity. If the demand increases, the average buffer occupancy will increase as well. Measurements have shown that the total throughput increases as well. If the buffer occupancy is zero or very low, transmission opportunities on network links can be missed. This is not the case when the buffer occupancy is small but non zero. However, if the buffer occupancy continues to increase, the buffer becomes overloaded and the throughput does not increase anymore. When the buffer occupancy is close to the maximum, the throughput may decrease. This drop in throughput can be caused by excessive retransmissions of reliable protocols that incorrectly assume that previously sent packets have been lost while they are still waiting in the buffer. The network delay on the other hand increases with the buffer occupancy. In practice, a good operating point for a network buffer is a low occupancy to achieve high link utilization and also low delay for interactive applications.
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