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../../exercises/ipv6.rst:481
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The packets whose destinations are ``A1``, ``A2``, ``B1`` or ``B2`` are never forwarded via router ``R4``
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../../exercises/routing-protocols.rst:598
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Besides :manpage:`ping6(8)` and :manpage:`traceroute6(8)`, it is also useful to interact with the BGP daemon that runs on each of our routers. This is done by connecting on the Command Line Interface of the BGP router using telnet.
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../../exercises/tcp-2.rst:646
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the value of the duplicate acknowledgment threshold is fixed and set to 3
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../../protocols/bgp.rst:159
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In this figure, the router receives BGP messages on the left part of the figure, processes these messages and possibly sends BGP messages on the right part of the figure. A BGP router contains three important data structures :
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../../protocols/congestion.rst:225
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`CUBIC`, which was designed for high bandwidth links and is the default congestion control scheme in Linux since the Linux 2.6.19 kernel [HRX2008]_. It is now used by several operating systems and is becoming the default congestion control scheme :rfc:`8312`. A key difference between CUBIC and the TCP congestion control scheme described in this chapter is that CUBIC is much more aggressive when probing the network. Instead of relying on additive increase after a fast recovery, a CUBIC sender adjusts its congestion by using a cubic function. Thanks to this function, the congestion windows grows faster. This is particularly important in high-bandwidth delay networks.
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../../protocols/email.rst:230 • ../../protocols/email.rst:230 • ../../protocols/email.rst:230 • ../../protocols/email.rst:230 • ../../protocols/email.rst:278 • ../../protocols/email.rst:297 • ../../protocols/email.rst:311
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Encoding
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../../protocols/ethernet.rst:195
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Initially, the OUIs were allocated by Xerox [DP1981]_. However, once Ethernet became an IEEE and later an ISO standard, the allocation of the OUIs moved to IEEE. The list of all OUI allocations may be found at http://standards.ieee.org/regauth/oui/index.shtml
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../../protocols/http.rst:175
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The importance of the `Host:` header line
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../../protocols/ipv6.rst:174
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In practice, there are several types of IPv6 unicast address. Most of the `IPv6 unicast addresses <http://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml>`_ are allocated in blocks under the responsibility of IANA_. The current IPv6 allocations are part of the `2000::/3` address block. Regional Internet Registries (RIR) such as RIPE_ in Europe, ARIN_ in North-America or AfriNIC in Africa have each received a `block of IPv6 addresses <http://www.iana.org/assignments/ipv6-unicast-address-assignments/ipv6-unicast-address-assignments.xhtml>`_ that they sub-allocate to Internet Service Providers in their region. The ISPs then sub-allocate addresses to their customers.
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../../protocols/ethernet.rst:174
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10 Mb/s over optical fiber
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../../protocols/routing.rst:158
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To efficiently spread the load over different paths, routers need to implement `per-flow` load-balancing. This implies that they must forward all the packets that belong to the same flow on the same path. Since a TCP connection is always identified by the four-tuple (source and destination addresses, source and destination ports), one possibility would be to select an outgoing interface upon arrival of the first packet of the flow and store this decision in the router's memory. Unfortunately, such a solution does not scale since the required memory grows with the number of TCP connections that pass through the router.
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../../protocols/tcp.rst:159
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TCP connection establishment can be described as the four state Finite State Machine shown below. In this FSM, `!X` (resp. `?Y`) indicates the transmission of segment `X` (resp. reception of segment `Y`) during the corresponding transition. `Init` is the initial state.
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../../protocols/tls.rst:250
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An important difference between ``DHE_RSA`` and ``RSA`` is their reaction against attacks. ``DHE_RSA`` is considered by many to be stronger than ``RSA`` because it supports `Perfect Forward Secrecy`. This property is important against attackers that are able to eavesdrop all the (encrypted) data sent and received by a server. Consider that Terrence is such an attacker that has stored all the packets exchanged by Bob's server during the last six months. If he manages, by any means, to obtain Bob's private key, he will be able to decrypt all the keys used to secure the TLS sessions with Bob's server during this period. With ``DHE_RSA``, a similar attack is less devastating. If Terrence knows Bob's private key, he will be able to launch a man-in-the-middle attack against future TLS sessions with Bob's server. However, he will not be able to recover the keys used for all the past sessions that he captured.
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../../protocols/wifi.rst:141
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A first type of management frames are the `beacon` frames. These frames are broadcasted regularly by access points. Each `beacon frame` contains information about the capabilities of the access point (e.g. the supported 802.11 transmission rates) and a `Service Set Identity` (SSID). The SSID is a null-terminated ASCII string that can contain up to 32 characters. An access point may support several SSIDs and announce them in beacon frames. An access point may also choose to remain silent and not advertise beacon frames. In this case, WiFi stations may send `Probe request` frames to force the available access points to return a `Probe response` frame.
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../../bibliography.rst:318
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Scheifler, R., Gettys, J., `X Window System: The Complete Reference to Xlib <http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/V51B_ACRO_SUP/XWINSYS.PDF>`_, X Protocol, ICCCM, XLFD, X Version 11, Release 4, Digital Press
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../../glossary.rst:200
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The File Transfer Protocol is defined in :rfc:`959`
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../../principles/network.rst:217
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the `control packets`
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../../principles/reliability.rst:215
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Given that multi-symbol encodings cannot be used by all physical layers, a generic solution which can be used with any physical layer that is able to transmit and receive only bits `0` and `1` is required. This generic solution is called `stuffing` and two variants exist : `bit stuffing` and `character stuffing`. To enable a receiver to easily delineate the frame boundaries, these two techniques reserve special bit strings as frame boundary markers and encode the frames so that these special bit strings do not appear inside the frames.
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../../principles/transport.rst:125
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Most networks use a datagram organization and provide a simple service which is called the `connectionless service`.
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../../principles/sharing.rst:203
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Dropping and marking packets is not the only possible reaction of a router that becomes congested. A router could also selectively delay packets belonging to some flows. There are different algorithms that can be used by a router to delay packets. If the objective of the router is to fairly distribute to bandwidth of an output link among competing flows, one possibility is to organize the buffers of the router as a set of queues. For simplicity, let us assume that the router is capable of supporting a fixed number of concurrent flows, say `N`. One of the queues of the router is associated to each flow and when a packet arrives, it is placed at the tail of the corresponding queue. All the queues are controlled by a `scheduler`. A `scheduler` is an algorithm that is run each time there is an opportunity to transmit a packet on the outgoing link. Various schedulers have been proposed in the scientific literature and some are used in real routers.
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