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../../principles/network.rst:269
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This hierarchical allocation of addresses can be applied in any type of network. In practice, the allocation of the addresses must follow the network topology. Usually, this is achieved by dividing the addressing space in consecutive blocks and then allocating these blocks to different parts of the network. In a small network, the simplest solution is to allocate one block of addresses to each network node and assign the host addresses from the attached node.
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../../principles/reliability.rst:236
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`Bit stuffing` can be easily implemented in hardware. However, implementing it in software is difficult given the complexity of performing bit manipulations in software. Software implementations prefer to process characters than bits, software-based datalink layers usually use `character stuffing`. This technique operates on frames that contain an integer number of characters. In computer networks, characters are usually encoded by relying on the :term:`ASCII` table. This table defines the encoding of various alphanumeric characters as a sequence of bits. :rfc:`20` provides the ASCII table that is used by many protocols on the Internet. For example, the table defines the following binary representations :
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../../principles/sharing.rst:265
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The common problem among Local Area Networks is how to efficiently share the available bandwidth. If two devices send a frame at the same time, the two electrical, optical or radio signals that correspond to these frames will appear at the same time on the transmission medium and a receiver will not be able to decode either frame. Such simultaneous transmissions are called `collisions`. A `collision` may involve frames transmitted by two or more devices attached to the Local Area Network. Collisions are the main cause of errors in wired Local Area Networks.
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../../principles/security.rst:747
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The protocol described above works, but it takes a long time for Bob to authenticate Alice and for Alice to authenticate Bob. A faster authentication could be the following.
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../../exercises/ipv6.rst:609
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We use five /64 IPv6 prefixes in this network topology:
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../../exercises/routing-protocols.rst:861
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The ``UPDATE`` message can be used to withdraw and advertise routes. The packet below is sent by ``AS2`` to advertise its route towards `2001:cafe:2::/48` on the BGP session with ``AS1``.
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../../exercises/tcp-2.rst:837
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A TCP connection has been active for some time and has reached a congestion window of 4000 bytes. Four segments are sent, but the second (shown in red in the figure) is corrupted. Complete the time-sequence diagram.
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../../protocols/bgp.rst:271
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Utilization of the BGP nexthop attribute
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../../protocols/email.rst:234
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../../protocols/ethernet.rst:293
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The `MAC address learning` algorithm combined with the forwarding algorithm work well in a tree-shaped network such as the one shown above. However, to deal with link and switch failures, network administrators often add redundant links to ensure that their network remains connected even after a failure. Let us consider what happens in the Ethernet network shown in the figure below.
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../../protocols/http.rst:255
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This problem was solved by extending HTTP to support persistent TCP connections :rfc:`2616`. A persistent connection is a TCP connection over which a client may send several HTTP requests. This is illustrated in the figure below showing the persistent connection of HTTP 1.1.
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../../protocols/ipv6.rst:217
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a packet with destination ``2001:6a8:3080::1234`` matches three routes : ``::/0``, ``2001:6a8::/32`` and ``2001:6a8:3080::/48``. The packet is forwarded via gateway ``fe80::bad:cafe``
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../../protocols/ethernet.rst:193
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Additional information about the history of the Ethernet technology may be found at http://ethernethistory.typepad.com/
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../../protocols/tcp.rst:215
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As explained earlier, TCP segments may contain an optional header extension. In the `SYN` and `SYN+ACK` segments, these options are used to negotiate some parameters and the utilization of extensions to the basic TCP specification.
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../../protocols/tls.rst:335
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a `Protocol Version` field that indicates the version of the TLS protocol used. This version is composed of two sub fields : a major and a minor version number.
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../../glossary.rst:241
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ICANN
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../../principles/network.rst:295
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In the above figure, assume that the network uses 16 bits addresses and that the prefix `01001010` has been assigned to the entire network. Since the network contains four routers, the network operator could assign one block of sixty-four addresses to each router. `R1` would use address `0100101000000000` while `A` could use address `0100101000000001`. `R2` could be assigned all addresses from `0100101001000000` to `0100101001111111`. `R4` could then use `0100101011000000` and assign `0100101011000001` to `B`. Other allocation schemes are possible. For example, `R3` could be allocated a larger block of addresses than `R2` and `R4` could use a sub-block from `R3` 's address block.
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../../principles/reliability.rst:238
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`A` : `1000011` b
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../../principles/transport.rst:219
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Transport layer services
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../../principles/sharing.rst:267
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All Local Area Network technologies rely on a `Medium Access Control` algorithm to regulate the transmissions to either minimize or avoid collisions. There are two broad families of `Medium Access Control` algorithms :
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