Exit Zen
23
../../exercises/ex-sharing.rst:558
English
In this network, compute the minimum round-trip-time between `A` (resp. `B`) and `D`. Perform the computation if the hosts send segments containing 1000 bits.
0/1580 · 158
23
../../exercises/reliability.rst:52
English
Reliable protocols depend on error detection algorithms to detect transmission errors. The following questions will reinforce your understanding of these algorithms.
186/1650 · 165
23
../../exercises/network.rst:208 • ../../exercises/network.rst:238
English
The network operator would like to use the following paths :
59/600 · 60
23
../../exercises/transport.rst:148
English
What is piggybacking and what are the benefits of this technique ?
78/660 · 66
23
../../principles/naming.rst:119
English
DNS resolvers have several advantages over letting each Internet host query directly nameservers. Firstly, regular Internet hosts do not need to maintain the up-to-date list of the addresses of the root servers. Secondly, regular Internet hosts do not need to send queries to nameservers all over the Internet. Furthermore, as a DNS resolver serves a large number of hosts, it can cache the received answers. This allows the resolver to quickly return answers for popular DNS queries and reduces the load on all DNS servers [JSBM2002]_.
643/5360 · 536
23
../../principles/referencemodels.rst:99 • ../../principles/referencemodels.rst:109
English
The Application layer
21/210 · 21
23
../../principles/network.rst:91
English
To understand the datagram organization, let us consider the figure below. A network layer address, represented by a letter, has been assigned to each host and router. To send some information to host `J`, host `A` creates a packet containing its own address, the destination address and the information to be exchanged.
334/3200 · 320
23
../../principles/reliability.rst:62
English
set the voltage on the electrical wire at ``+5V`` during one millisecond to transmit a bit set to `1`
108/1010 · 101
23
../../principles/sharing.rst:129
English
In the network above, consider the case where host `A` is transmitting packets to destination `C`. `A` can send one packet per second and its packets will be delivered to `C`. Now, let us explore what happens when host `B` also starts to transmit a packet. Node `R1` will receive two packets that must be forwarded to `R2`. Unfortunately, due to the limited bandwidth on the `R1-R2` link, only one of these two packets can be transmitted. The outcome of the second packet will depend on the available buffers on `R1`. If `R1` has one available buffer, it could store the packet that has not been transmitted on the `R1-R2` link until the link becomes available. If `R1` does not have available buffers, then the packet needs to be discarded.
0/7410 · 741
23
../../protocols/dns.rst:80
English
Footnotes
21/100 · 9
23
../../principles/security.rst:301
English
Unfortunately, it is difficult to use this cipher in practice since the key must be as long as the message that needs to be transmitted. If the key is smaller than the message and the message is divided into blocks that have the same length as the key, then the scheme becomes less secure since the same key is used to decrypt different parts of the message. In practice, `XOR` is often one of the basic operations used by encryption schemes. To be usable, the deployed encryption schemes use keys that are composed of a small number of bits, typically 56, 64, 128, 256, ...
0/5740 · 574
23
../../exercises/dns.rst:61
English
When `dig` is run, the header section in its output indicates the `id` the DNS identifier used to send the query. Does your implementation of `dig` generates random identifiers ?
0/1780 · 178
23
../../exercises/ipv6.rst:195
English
Consider a slightly different network than in the previous question.
0/680 · 68
23
../../exercises/lan.rst:248
English
The second part of the output provides the state of each switch port. Port ``s3-eth1`` is active and forwards data frames (state is set to `forwarding`). This port is a `designated` port. The cost of ``1`` is the cost associated to this interface. The same information is found for port ``s3-eth2``.
0/2990 · 299
23
../../exercises/routing-policies.rst:195
English
`Section 3.1 <https://tools.ietf.org/html/rfc4443#section-3.1>`_ of :rfc:`4443` seven different Codes for the ICMPv6 Destination Unreachable Message. Under which circumstances would a router generate such an ICMPv6 message with :
0/2290 · 229
23
../../exercises/routing-protocols.rst:272
English
Exploring RIP
0/130 · 13
23
../../exercises/tcp-2.rst:125
English
We can now close the connection gracefully. Let us first issue inject a segment with the ``FIN`` flag set.
0/1060 · 106
23
../../exercises/trace.rst:114
English
You can now use your understanding of wireshark_ and tcpdump_ to analyze a 2-minutes long packet trace.
0/1030 · 103
23
../../protocols/bgp.rst:78
English
the `import filter` that specifies, for each peering relationship, the routes that can be accepted from the neighboring domain (the non-acceptable routes are ignored and the domain never uses them to forward packets)
0/2160 · 216
23
../../protocols/congestion.rst:118
English
The third difficulty is to allow an ECN-capable sender to detect whether the remote host also supports ECN. This is a classical negotiation of extensions to a transport protocol. In TCP, this could have been solved by defining a new TCP option used during the three-way handshake. To avoid wasting space in the TCP options, the designers of ECN opted in :rfc:`3168` for using the `ECN-Echo` and `CWR` bits in the TCP header to perform this negotiation. In the end, the result is the same with fewer bits exchanged.
0/5140 · 514