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../../protocols/tcp.rst:135
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Establishment of a TCP connection
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../../protocols/tls.rst:192
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the ``ServerHello`` message that contains the protocol version chosen by the server (assumed to be the same as the client version in this chapter), the 32 random bytes chosen by the server, the `Cipher Suite` selected by the server from the list advertised by the client and a `Session Id`. This `Session Id` is an identifier which is chosen by the server. It identifies the TLS session and the security parameters (algorithms and keys) negotiated for this session. It is used to support session resumption.
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../../protocols/wifi.rst:109
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802.11 control frames are simpler than data frames. They contain a `Frame Control`, a `Duration` field and one or two addresses. The acknowledgment frames are very small. They only contain the address of the destination of the acknowledgment. There is no source address and no `Sequence Control` field in the acknowledgment frames. This is because the acknowledgment frame can easily be associated to the previous frame that it acknowledges. Indeed, each unicast data frame contains a `Duration` field that is used to reserve the transmission channel to ensure that no collision will affect the acknowledgment frame. The `Sequence Control` field is mainly used by the receiver to remove duplicate frames. Duplicate frames are detected as follows. Each data frame contains a 12 bits sequence number in the `Sequence Control` field and the `Frame Control` field contains the `Retry` bit flag that is set when a frame is transmitted. Each 802.11 receiver stores the most recent sequence number received from each source address in frames whose `Retry` bit is reset. Upon reception of a frame with the `Retry` bit set, the receiver verifies its sequence number to determine whether it is a duplicated frame or not.
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../../bibliography.rst:147
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Rago, S., `UNIX System V network programming <http://www.pearsonhighered.com/educator/product/UNIX-System-V-Network-Programming/9780201563184.page>`_, Addison Wesley, 1993
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../../glossary.rst:63
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frame
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../../principles/network.rst:153
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Learning the location of the sources is not sufficient, nodes also need to forward packets towards their destination. When a node receives a packet whose destination address is already present inside its port-address table, it simply forwards the packet on the interface listed in the port-address table. In this case, the packet will follow the port-address table entries in the downstream nodes and will reach the destination. If the destination address is not included in the port-address table, the node simply forwards the packet on all its interfaces, except the interface from which the packet was received. Forwarding a packet over all interfaces is usually called `broadcasting` in the terminology of computer networks. Sending the packet over all interfaces except one is a costly operation since the packet is sent over links that do not reach the destination. Given the tree-shape of the network, the packet will explore all downstream branches of the tree and will finally reach its destination. In practice, the `broadcasting` operation does not occur too often and its performance impact remains limited.
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../../principles/reliability.rst:194
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To enable the transmission/reception of frames, the first problem to be solved is how to encode a frame as a sequence of bits, so that the receiver can easily recover the received frame despite the limitations of the physical layer.
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../../principles/security.rst:447
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MD5, originally proposed in :rfc:`1321`. It has been used in a wide range of applications. In 2010, attacks against MD5 were published and this hash function is now deprecated.
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../../exercises/ipv6.rst:473
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``p:0000::/64`` used on the link ``A1-R1``. ``A1`` uses address ``p:0000::A1/64``
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../../exercises/routing-protocols.rst:529
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Remember that BGP is a distributed protocol and that it takes some time to launch the daemons and exchange the messages. After some time, the same command will confirm that everything works as expected.
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../../exercises/tcp-2.rst:639
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Unless otherwise noted, we assume for the questions in this section that the following conditions hold.
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../../protocols/bgp.rst:133
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the set of attributes (e.g. AS-Path) associated to the advertised prefixes
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../../protocols/congestion.rst:214
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In general, the maximum throughput that can be achieved by a TCP connection depends on its maximum window size and the round-trip-time if there are no losses. If there are losses, it depends on the MSS, the round-trip-time and the loss ratio.
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../../protocols/email.rst:216
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`application`. The message part contains binary information that was produced by the particular application listed as the subtype. Email clients use the subtype to launch the application that is able to decode the received binary information.
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../../protocols/ethernet.rst:179 • ../../protocols/ethernet.rst:358
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10 Gbps
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../../protocols/http.rst:166
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the `Last-Modified:` header indicates the date and time of the last modification of the document attached to the HTTP response.
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../../protocols/ipv6.rst:159
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The subnet identifier plays a key role in the scalability of network layer addressing architecture. An important point to be defined in a network layer protocol is the allocation of the network layer addresses. A naive allocation scheme would be to provide an address to each host when the host is attached to the Internet on a first come first served basis. With this solution, a host in Belgium could have address ``2001:db8::1`` while another host located in Africa would use address ``2001:db8::2``. Unfortunately, this would force all routers on the Internet to maintain one route towards each host. In the network layer, scalability is often a function of the number of routes stored on the router. A network will usually work better if its routers store fewer routes and network administrators usually try to minimize the number of routes that are known by their routers. For this, they often divide their network prefix in smaller blocks. For example, consider a company with three campuses, a large one and two smaller ones. The network administrator would probably divide his block of addresses as follows :
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../../protocols/ethernet.rst:171
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Thick coaxial cable, 500m
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../../protocols/routing.rst:143
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the routers that are adjacent to the failure detect it quickly. The default solution is to rely on the regular exchange of HELLO packets. However, the interval between successive HELLOs is often set to 10 seconds... Setting the HELLO timer down to a few milliseconds is difficult as HELLO packets are created and processed by the main CPU of the routers and these routers cannot easily generate and process a HELLO packet every millisecond on each of their interfaces. A better solution is to use a dedicated failure detection protocol such as the Bidirectional Forwarding Detection (BFD) protocol defined in [KW2009]_ that can be implemented directly on the router interfaces. Another solution to be able to detect the failure is to instrument the physical and the datalink layer so that they can interrupt the router when a link fails. Unfortunately, such a solution cannot be used on all types of physical and datalink layers.
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../../protocols/tcp.rst:137
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In the figure above, the connection is considered to be established by the client once it has received the `SYN+ACK` segment, while the server considers the connection to be established upon reception of the `ACK` segment. The first data segment sent by the client (server) has its `sequence number` set to `x+1` (resp. `y+1`).
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