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16 ../../exercises/sockets.rst:137
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Receiving data from a peer using a socket 41/10000 · 41
16 ../../principles/naming.rst:84
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — This hierarchical naming scheme is a key component of the Domain Name System (DNS). The DNS is a distributed database that contains mappings between fully qualified domain names and addresses. The DNS uses the client-server model. The clients are hosts or applications that need to retrieve the mapping for a given name. Each :term:`nameserver` stores part of the distributed database and answers the queries sent by clients. There is at least one :term:`nameserver` that is responsible for each domain. In the figure below, domains are represented by circles and there are three hosts inside domain `dom` (`h1`, `h2` and `h3`) and three hosts inside domain `a.sdom1.dom`. As shown in the figure below, a sub-domain may contain both host names and sub-domains. 760/10000 · 760
16 ../../principles/network.rst:93
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `virtual circuits` 18/10000 · 18
16 ../../principles/referencemodels.rst:100
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The `Datalink layer` allows directly connected hosts to exchange information, but it is often necessary to exchange information between hosts that are not attached to the same physical medium. This is the task of the `network layer`. The `network layer` is built above the `datalink layer`. Network layer entities exchange `packets`. A `packet` is a finite sequence of bytes that is transported by the datalink layer inside one or more frames. A packet usually contains information about its origin and its destination, and usually passes through several intermediate devices called routers on its way from its origin to its destination. 637/10000 · 637
16 ../../principles/reliability.rst:52
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — :math:`10^6` 12/10000 · 12
16 ../../exercises/network.rst:112
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Assume that the routers located in `Denver` and `Kansas City` need to exchange lots of packets. Can you configure the link metrics such that the link between these two routers does not carry any packet sent by another router in the network ? 241/10000 · 241
16 ../../exercises/reliability.rst:33
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — there are no transmission errors 32/10000 · 32
16 ../../glossary.rst:96
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — ASN.1 5/10000 · 5
16 ../../exercises/transport.rst:134
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Amazon provides the `S3 storage service <https://s3.amazonaws.com/>`_ where companies and researchers can store lots of information and perform computations on the stored information. Amazon allows users to send files through the Internet, but also by sending hard-disks. Assume that a 1 Terabyte hard-disk can be delivered within 24 hours to Amazon by courier service. What is the minimum bandwidth required to match the bandwidth of this courier service ? 457/10000 · 457
16 ../../principles/sharing.rst:155 • ../../principles/sharing.rst:223
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Network congestion 18/10000 · 18
16 ../../principles/transport.rst:59
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Trudy : `1234` 14/10000 · 14
16 ../../principles/security.rst:213
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — When designing network protocols and applications that will be deployed on a large scale, it is important to take those DDoS attacks into account. Attackers use different strategies to launch DDoS attacks. Some have managed to gain control of a large number of sources by injecting malware on them. Others, and this is where protocol designers have an important role to play, simply exploit design flaws in some protocols. Consider a simple request-response protocol where the client sends a request and the server replies with a response. Often the response is larger or much larger than the request sent by the client. Consider that such a simple protocol is used over a datagram network. When Alice sends a datagram to Bob containing her request, Bob extracts both the request and Alice's address from the packet. He then sends his response in a single packet destined to Alice. Mallory would like to create a DoS attack against Alice without being identified. Since he has studied the specification of this protocol, he can send a request to Bob inside a packet having Alice's address as its source address. Bob will process the request and send his (large) response to Alice. If the response has the same size as the request, Mallory is producing a `reflection attack` since his packets are reflected by Bob. Alice would think that she is attacked by Bob. If there are many servers that operate the same service as Bob, Mallory could hide behind a large number of such reflectors. Unfortunately, the reflection attack can also become an amplification attack. This happens when the response sent by Bob is larger than the request that it has received. If the response is :math:`k` times larger than the request, then when Mallory consumes 1 Gbps of bandwidth to send requests, his victim receives :math:`k` Gbps of attack traffic. Such amplification attacks are a very important problem and protocol designers should ensure that they never send a large response before having received the proof that the request that they have received originated from the source indicated in the request. 2092/10000 · 2092
16 ../../exercises/dns.rst:50
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Assume now that you are residing in a network where there is no DNS resolver and that you need to perform your query manually starting from the DNS root. 153/10000 · 153
16 ../../exercises/http.rst:51
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The minimum command sent to a HTTP server is `GET / HTTP/1.0` followed by CRLF and a blank line. 96/10000 · 96
16 ../../exercises/ipv6.rst:91
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — In this network, propose the forwarding tables of ``R2`` and ``R3`` that ensure that hosts ``A`` and ``B`` can exchange packets in both directions. 147/10000 · 147
16 ../../exercises/lan.rst:115
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Testing the Spanning Tree with IPMininet 40/10000 · 40
16 ../../exercises/routing-policies.rst:155
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Propose a configuration on R1 that achieves the same objective as the one shown in the figure but also preserves the reachability of all IP addresses inside `AS456` if one of `AS456`'s interdomain links fails. 209/10000 · 209
16 ../../exercises/routing-protocols.rst:245
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The Hello packet contains some parameters such as the `Hello interval` that is set to 1 second. This interval is the delay between the transmission of successive Hello packets. Since the `Router Dead Interval` is set to 3 seconds, the router will consider the link as down if it does not receive Hello packets during a period of 3 seconds. The second packet of the trace is sent by router ``r1``. 396/10000 · 396
16 ../../exercises/tcp-2.rst:88
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The description of TCP packets in packetdrill_ uses a syntax that is very close to the tcpdump_ one. The ``+0`` timing indicates that the line is executed immediately after the previous event. The ``<`` sign indicates that packetdrill_ injects a TCP segment and the ``S`` character indicates that the ``SYN`` flag must be set. Like tcpdump_, packetdrill_ uses sequence numbers that are relative to initial sequence number. The three numbers that follow are the sequence number of the first byte of the payload of the segment (``0``), the sequence number of the last byte of the payload of the segment (``0`` after the semi-column) and the length of the payload (``0`` between brackets) of the ``SYN`` segment. This segment does not contain a valid acknowledgment but advertises a window of 1000 bytes. All ``SYN`` segments must also include the ``MSS`` option. In this case, we set the MSS to 1000 bytes. The next line of the packetdrill_ script verifies the reply sent by the instrumented Linux kernel. 1003/10000 · 1003
16 ../../exercises/trace.rst:96
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — wireshark_ is very good at displaying packets, but it also contains several analysis tools that can be very useful. The first tool is `Follow TCP stream`. It is part of the `Analyze` menu and allows you to reassemble and display all the payload exchanged during a TCP connection. This tool can be useful if you need to analyze for example the commands exchanged during an HTTP or SMTP session. 393/10000 · 393