Exit Zen
13
../../protocols/http2.rst:70
English
A closer look at the average web page shows that it contains, on average, 27 KBytes of HTML, 120 KBytes of fonts, 60 KBytes of CSS information, almost 1 MBytes of images and more than 400 KBytes of javascript. Each of these web page requires about 70 different HTTP requests. In other words, a browser needs to send on average 70 requests to retrieve a complete web page.
0/3720 · 372
13
../../protocols/ipv6.rst:89
English
TUBA proposed in :rfc:`1347` and :rfc:`1561`
0/440 · 44
13
../../protocols/ppp.rst:34 • ../../protocols/ethernet.rst:192 • ../../protocols/ethernet.rst:308 • ../../protocols/wifi.rst:157
English
Footnotes
0/100 · 9
13
../../protocols/ppp.rst:37
English
The IANA maintains the registry of all assigned PPP protocol fields at : http://www.iana.org/assignments/ppp-numbers
0/1160 · 116
13
../../protocols/routing.rst:40
English
RIP routers periodically exchange RIP messages. The format of these messages is shown below. A RIP message is sent inside a UDP segment whose destination port is set to `521`. A RIP message contains several fields. The `command` field indicates whether the RIP message is a request or a response. When a router boots, its routing table is empty and it cannot forward any packet. To speedup the discovery of the network, it can send a request message to the RIP IPv6 multicast address, ``FF02::9``. All RIP routers listen to this multicast address and any router attached to the subnet will reply by sending its own routing table as a sequence of RIP messages. In steady state, routers multicast one of more RIP response messages every 30 seconds. These messages contain the distance vectors that summarize the router's routing table. The current version of RIP is version 2 defined in :rfc:`2453` for IPv4 and :rfc:`2080` for IPv6.
0/9310 · 931
13
../../protocols/rpc.rst:34
English
The eXternal Data Representation (XDR) Standard, defined in :rfc:`1832` is an early specification that describes how information exchanged during Remote Procedure Calls should be encoded before being transmitted through a network. Since the transport service enables transfering a block of bytes (with the connectionless service) or a stream of bytes (by using the connection-oriented service), XDR maps each datatype onto a sequence of bytes. The caller encodes each data in the appropriate sequence and the callee decodes the received information. Here are a few examples extracted from :rfc:`1832` to illustrate how this encoding/decoding can be performed.
0/6590 · 659
13
../../protocols/ssh.rst:89
English
The IANA_ maintains a `list of the cryptographic algorithms <http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xhtml#ssh-parameters-16>`_ that can be used by ``ssh`` implementations. For each type of algorithm, the client provides an ordered list of the algorithms that it supports and agrees to use. The server compares the received list with its own list. The outcome of the negotiation is a set of four algorithms [#fnull]_ that will be combined for this session.
0/4780 · 478
13
../../protocols/tcp.rst:37
English
the `source and destination ports`. The source and destination ports play an important role in TCP, as they allow the identification of the connection to which a TCP segment belongs. When a client opens a TCP connection, it typically selects an ephemeral TCP port number as its source port and contacts the server by using the server's port number. All the segments that are sent by the client on this connection have the same source and destination ports. The server sends segments that contain as source (resp. destination) port, the destination (resp. source) port of the segments sent by the client (see figure :ref:`fig-tcpports`). A TCP connection is always identified by four pieces of information :
0/7060 · 706
13
../../protocols/tls.rst:44
English
143
0/100 · 3
13
../../protocols/transport-service.rst:47
English
Textual representation of IPv6 addresses
0/400 · 40
13
../../protocols/udp.rst:55
English
a 16 bits length field
0/220 · 22
13
../../protocols/wifi.rst:22
English
0.9 Mbps
0/100 · 8
14
../../bibliography.rst:48
English
Clark D., `The Design Philosophy of the DARPA Internet Protocols <https://dx.doi.org/10.1145/205447.205458>`_, Computer Communications Review 18:4, August 1988, pp. 106-114
0/1720 · 172
14
../../exercises/ex-sharing.rst:290
English
Consider again a network that uses CSMA/CD. This time, the bandwidth is set to 1 Gbps and the cable has a length of two kilometers. When a collision occurs, consider that the hosts B and C retransmit immediately while host A waits for the next slot.
0/2490 · 249
14
../../principles/security.rst:187
English
The last type of attack that we consider in this introduction are the `Denial of Service` or DoS attacks. During such an attack, the attacker generates enough packets to saturate a given service and prevent it from operating correctly. The simplest Denial of Service attack is to send more packets that the bandwidth of the link that attaches the target to the network. The target could be a single server, a company or even an entire country. If these packets all come from the same source, then the victim can identify the attacker and contact the law enforcement authorities. In practice, such denial of service attacks do not originate from a single source. The attacker usually compromises a (possibly very large) set of sources and forces them to send packets to saturate a given target. Since the attacking traffic comes from a wide range of sources, it is difficult for the victim to locate the culprit and also to counter the attack. Saturating a link is the simplest example of `Distributed Denial of Service (DDoS)` attacks.
0/10350 · 1035
14
../../exercises/dns.rst:45
English
What is the IPv6 address that corresponds to `www.computer-networking.info` ? Which type of DNS query does `dig` send to obtain this information ?
0/1460 · 146
14
../../exercises/http.rst:37
English
As for the DNS, besides using software tools that implement the HTTP protocols, it can also be useful to analyze packet traces with wireshark_ . The exercises below contain simple packet traces collected with different versions of the HTTP protocol.
0/2490 · 249
14
../../exercises/ipv6.rst:43 • ../../exercises/ipv6.rst:152
English
router ``R4`` uses address ``2001:db8:1341:34::4`` on its West interface, address ``2001:db8:1341:24::4`` on its North interface and address ``2001:db8:1341:4::4`` on its East interface
0/1850 · 185
14
../../exercises/lan.rst:91
English
Fig. 5. Will the link between `S0` and `S1` ever be used?
0/570 · 57
14
../../exercises/routing-policies.rst:151
English
Via which provider does `AS456` receive the packets destined to ``2001:db8:caff::bb`` and ``2001:db8:cafe::aa`` ?
0/1130 · 113