Exit Zen
86
../../protocols/tcp.rst:262
English
the remote TCP port number
0/260 · 26
86
../../protocols/tls.rst:454
English
For some applications, waiting one round-trip-time before being able to send data is too long. TLS 1.3 allows the client to send encrypted data immediately after the `ClientHello`, without having to wait for the `ServerHello` message. At this point in the handshake, the client cannot know the key that will be derived by the Diffie Hellman key exchange. The trick is that the server and the client need to have previously agreed on a `pre-shared-key`. This key could be negotiated out of band, but usually it was exchanged over a previous TLS session between the client and the server. Both the client and the server can store this key in their cache. When the client creates a new TLS session to a server, it checks whether it already knows a pre-shared key for this server. If so, the client announces the identifier of this key in its `ClientHello` message. Thanks to this identifier, the server can recover the key and use it to decrypt the 0-rtt Encrypted record. A simplified version of the 0-rtt TLS 1.3 handshake [#fhandshake]_ is shown in the figure below.
0/10660 · 1066
87
../../glossary.rst:144
English
IS-IS
0/100 · 5
87
../../principles/network.rst:363
English
the label for the outgoing packet
0/330 · 33
87
../../principles/reliability.rst:304
English
Recovering from transmission errors
0/350 · 35
87
../../principles/transport.rst:521
English
In the previous sections, we have described services that are provided by the transport layer. However, it is important to note that the notion of service is more general than in the transport layer. As explained earlier, the network layer also provides a service, which in most networks is an unreliable connectionless service. There are network layers that provide a connection-oriented service. Similarly, the datalink layer also provides services. Some datalink layers will provide a connectionless service. This will be the case in Local Area Networks for examples. Other datalink layers, e.g. in public networks, provide a connection oriented service.
0/6570 · 657
87
../../principles/sharing.rst:402
English
[KT1975]_ analyzes in detail the performance of several CSMA variants. Under some assumptions about the transmission channel and the traffic, the analysis compares ALOHA, slotted ALOHA, persistent and non-persistent CSMA. Under these assumptions, ALOHA achieves a channel utilization of only 18.4% of the channel capacity. Slotted ALOHA is able to use 36.6% of this capacity. Persistent CSMA improves the utilization by reaching 52.9% of the capacity while non-persistent CSMA achieves 81.5% of the channel capacity.
0/5160 · 516
87
../../principles/security.rst:951
English
Alice chooses a secret integer : :math:`a=8` and sends :math:`A= g^{a} \mod p= 5^{8} \mod 23=16` to Bob
0/1030 · 103
87
../../exercises/ipv6.rst:808
English
Another interesting mininet_ command is ``pingall`` it allows to check that any host can reach any other host inside the network. It executes a ping from any host to any other host inside the network topology.
0/2090 · 209
87
../../exercises/routing-protocols.rst:1272
English
Let us now consider another example, also implemented using an IPMininet_ script. The network contains eight ASes with one host per AS. This small Internet is shown below and the script is available from :download:`/exercises/ipmininet_scripts/ebgp-bug-3.py`.
0/2590 · 259
87
../../protocols/bgp.rst:346
English
Sometimes, the `local-pref` attribute is used to prefer a `cheap` link compared to a more expensive one. For example, in the network below, `AS1` could wish to send and receive packets mainly via its interdomain link with `AS4`.
0/2280 · 228
87
../../protocols/email.rst:242 • ../../protocols/email.rst:244
English
5
0/100 · 1
87
../../protocols/ethernet.rst:357
English
20000
0/100 · 5
87
../../protocols/ipv6.rst:337
English
`Next Header` : this 8-bit field indicates the type [#fianaprotocol]_ of header that follows the IPv6 header. It can be a transport layer header (e.g. `6` for TCP or `17` for UDP) or an IPv6 option.
0/1980 · 198
87
../../protocols/ethernet.rst:331
English
The switches exchange `BPDUs` to build the spanning tree. Intuitively, the spanning tree is built by first selecting the switch with the smallest `identifier` as the root of the tree. The branches of the spanning tree are then composed of the shortest paths that allow all of the switches that compose the network to be reached. The `BPDUs` exchanged by the switches contain the following information :
0/4020 · 402
87
../../protocols/tcp.rst:263
English
the current state of the TCP FSM
0/320 · 32
87
../../protocols/tls.rst:482
English
On the web, TLS clients use certificates to authenticate servers but the clients are not authenticated. However, there are environments such as enterprise networks where servers may need to authenticate clients as well. A popular deployment is to authenticate remote clients who wish to access the enterprise network through a Virtual Private Network service. Some of these services run above TLS (or more precisely a variant of TLS named DTLS that runs above UDP [MoR2004]_ but is outside the scope of this chapter). In such services, each client is authenticated thanks to a public key and a certificate that is trusted by the servers. To establish a TLS session, such a client needs to prove that it owns the public key associated with the certificate. This is done by the server thanks to the CertificateRequest message. The TLS handshake becomes the following one:
0/8690 · 869
88
../../glossary.rst:146
English
Intermediate System- Intermediate System. A link-state intradomain routing that was initially defined for the ISO CLNP protocol but was extended to support IP v4 and IP v6. IS-IS is often used in ISP networks. It is defined in [ISO10589]_
0/2380 · 238
88
../../principles/network.rst:365
English
For example, consider the `label forwarding table` of a network node below.
0/750 · 75
88
../../principles/reliability.rst:306
English
In this section, we develop a reliable datalink protocol running above the physical layer service. To design this protocol, we first assume that the physical layer provides a perfect service. We will then develop solutions to recover from the transmission errors.
0/2630 · 263