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36 ../../principles/transport.rst:91
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Most applications exchange strings that are composed of fixed or variable numbers of characters. A common solution to define the character strings that are acceptable is to define them as a grammar using a Backus-Naur Form (:term:`BNF`) such as the Augmented BNF defined in :rfc:`5234`. A BNF is a set of production rules that generate all valid character strings. For example, consider a networked application that uses two commands, where the user can supply a username and a password. The BNF for this application could be defined as shown in the figure below. 563/10000 · 563
36 ../../exercises/ipv6.rst:350
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — on router ``R2`` 16/10000 · 16
36 ../../exercises/routing-protocols.rst:436
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — ``AS1`` is assigned ``2001:cafe:1::/48`` 40/10000 · 40
36 ../../exercises/tcp-2.rst:326
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A TCP stack uses both the fast retransmit technique and retransmission timers. A retransmission timer can fire after a fast retransmit when several segments are lost. The example below shows a loss of two consecutive segments. This script is available from :download:`/exercises/packetdrill_scripts/frr-rto.pkt`. 312/10000 · 312
36 ../../protocols/bgp.rst:122
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The BGP protocol :rfc:`4271` defines several types of messages that can be exchanged over a BGP session : 105/10000 · 105
36 ../../protocols/congestion.rst:197
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Evolution of the congestion window with regular losses 54/10000 · 54
36 ../../protocols/email.rst:181
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `Content-Type: multipart/alternative`. This header line indicates that the MIME message contains several representations of the same information. For example, a `multipart/alternative` message may contain both a plain text and an HTML version of the same text. 260/10000 · 260
36 ../../protocols/ethernet.rst:175
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 100Base-Tx 10/10000 · 10
36 ../../protocols/http.rst:153
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the `POST` method can be used by a client to send a document to a server. The document is attached to the HTTP request as a MIME document. 138/10000 · 138
36 ../../protocols/ipv6.rst:126
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — ``2001:0db8:0000:cd30:0000:0000:0000:0000`` / ``60`` 52/10000 · 52
36 ../../protocols/ethernet.rst:118
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The introduction of the twisted pairs led to two major changes to Ethernet. The first change concerns the physical topology of the network. 10Base2 and 10Base5 networks are shared buses, the coaxial cable typically passes through each room that contains a connected computer. A 10BaseT network is a star-shaped network. All the devices connected to the network are attached to a twisted pair cable that ends in the telecom closet. From a maintenance perspective, this is a major improvement. The cable is a weak point in 10Base2 and 10Base5 networks. Any physical damage on the cable broke the entire network and when such a failure occurred, the network administrator had to manually check the entire cable to detect where it was damaged. With 10BaseT, when one twisted pair is damaged, only the device connected to this twisted pair is affected and this does not affect the other devices. The second major change introduced by 10BaseT was that is was impossible to build a 10BaseT network by simply connecting all the twisted pairs together. All the twisted pairs must be connected to a relay that operates in the physical layer. This relay is called an `Ethernet hub`. A `hub` is thus a physical layer relay that receives an electrical signal on one of its interfaces, regenerates the signal and transmits it over all its other interfaces. Some `hubs` are also able to convert the electrical signal from one physical layer to another (e.g. 10BaseT to 10Base2 conversion). 1474/10000 · 1474
36 ../../protocols/routing.rst:106
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The first summary advertisement provides precise information about the distance used to reach each prefix. However, all routers in the network have to maintain a route towards `2001:db8:aaaa:0000::/64` and a route towards `2001:db8:aaaa:0001::/64` that are both via router `RA`. The second advertisement would improve the scalability of OSPF by reducing the number of routes that are advertised across area boundaries. However, in practice this requires manual configuration on the border routers. 497/10000 · 497
36 ../../protocols/rpc.rst:122
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `data`: an optional field that provides additional information about the error. 79/10000 · 79
36 ../../protocols/ssh.rst:269
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Among the various features of the ``ssh`` protocol, it is interesting to mention how users are authenticated by the server. The ``ssh`` protocol supports the classical username/password authentication (but both the username and the password are transmitted over the secure encrypted channel). In addition, ``ssh`` supports two authentication mechanisms that rely on public keys. To use the first one, each user needs to generate his/her own public/private key pair and store the public key on the server. To be authenticated, the user needs to sign a message containing his/her public key by using his/her private key. The server can easily verify the validity of the signature since it already knows the user's public key. The second authentication scheme is designed for hosts that trust each other. Each host has a public/private key pair and stores the public keys of the other hosts that it trusts. This is typically used in environments such as university labs where each user could access any of the available computers. If Alice has logged on ``computer1`` and wants to execute a command on ``computer2``, she can create an ``ssh`` session on this computer and type (again) her password. With the host-based authentication scheme, ``computer1`` signs a message with its private key to confirm that it has already authenticated Alice. ``computer2`` would then accept Alice's session without asking her credentials. 1421/10000 · 1421
36 ../../protocols/tcp.rst:116
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Upon reception of this segment (which is often called a `SYN segment`), the server host replies with a segment containing : 123/10000 · 123
36 ../../protocols/tls.rst:150
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `Random number`: security protocols rely on random numbers. The client sends a 32 bytes long random number where usually four of these bytes correspond to the client's clock. This random number is used, together with the server's random number, as a seed to generate the security keys. 285/10000 · 285
36 ../../protocols/wifi.rst:54
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — An 802.11 infrastructure network 32/10000 · 32
36 ../../principles/security.rst:378
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — a decryption function, :math:`D_{p}`, that takes a key and a message as parameters 82/10000 · 82
36 ../../protocols/http2.rst:239
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — HTTP/2.0 is a new version of the HTTP protocol that still uses port 80. When a client contacts an HTTP server, it must be able to determine whether it supports HTTP/1.x or HTTP/2.0. If the client sends a binary encoded HTTP/2.0 request to a server that only supports the ASCII encoded HTTP/1.x, it could cause problems on the server and even crash it. To minimize the risk of crashing HTTP/1.x servers, an HTTP/2.0 session starts like an HTTP/1.1 session and the first request contains the `Connection`, `Upgrade` and `HTTP2-Settings` headers. An example of such a request to upgrade the version of HTTP is shown below. 619/10000 · 619
36 ../../principles/sharing.rst:232
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `What triggers a packet to be discarded ?` What are the conditions that lead a network node to decide to discard a packet? The simplest answer to this question is : `When the buffer is full`. Although this is a good congestion indication, it is probably not the best one from a performance viewpoint. An alternative is to discard packets when the buffer occupancy grows too much. In this case, it is likely that the buffer will become full shortly. Since packet discarding is an information that allows hosts to adapt their transmission rate, discarding packets early could allow hosts to react earlier and thus prevent congestion from happening. 646/10000 · 646