Exit Zen
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../../exercises/email.rst:13
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Telnet is a protocol that allows to obtain a terminal on a remote server. For this, telnet opens a TCP connection with the remote server on port 23. However, most `telnet` implementations allow the user to specify an alternate port as `telnet hosts port` When used with a port number as parameter, `telnet` opens a TCP connection to the remote host on the specified port. `telnet` can thus be used to test any server using an ASCII-based protocol on top of TCP. Note that if you need to stop a running `telnet` session, ``Ctrl-C`` will not work as it will be sent by `telnet` to the remote host over the TCP connection. On many `telnet` implementations you can type ``Ctrl-]`` to freeze the TCP connection and return to the telnet interface.
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../../exercises/http.rst:22
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Can you explain the different headers placed by curl_ in the request ?
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../../exercises/ipv6.rst:31
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Design questions
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../../exercises/lan.rst:31
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Consider the switched network shown in the figure below. Compute the Spanning Tree of this network.
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../../exercises/routing-policies.rst:59
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from `AS4` to `AS2`
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../../exercises/routing-protocols.rst:83
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We use this mininet_ topology to collect packet traces that show the packets that OSPF routers exchange. For this, we add the following ``post_build`` method that IPMininet_ starts after having constructed the network and before launching the daemons. It simply starts tcpdump_ on each router to collect the first 100 OSPF packets that they send/receive.
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../../exercises/tcp-2.rst:20
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Let us start with a very simple example that uses packetdrill_ to open a TCP connection on a server running on the Linux kernel. A packetdrill_ script is a sequence of lines that are executed one after the other. There are three main types of lines in a packetdrill_ script.
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../../exercises/tcp.rst:52
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With your knowledge of TCP, you should now be able to reorder all the segments exchanged over a TCP connection.
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../../exercises/trace.rst:28
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The ``-6`` parameter passed to curl_ forces the utilization of IPv6. curl_ returns an HTML page that indicates that https must be used instead of http to access this web site.
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../../protocols/bgp.rst:21
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Domains need to be interconnected to allow a host inside a domain to exchange IP packets with hosts located in other domains. From a physical perspective, domains can be interconnected in two different ways. The first solution is to directly connect a router belonging to the first domain with a router inside the second domain. Such links between domains are called private interdomain links or `private peering links`. In practice, for redundancy or performance reasons, distinct physical links are usually established between different routers in the two domains that are interconnected.
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../../protocols/congestion.rst:22
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A key question that must be answered by any congestion control scheme is how congestion is detected. The first implementations of the TCP congestion control scheme opted for a simple and pragmatic approach : packet losses indicate congestion. If the network is congested, router buffers are full and packets are discarded. In wired networks, packet losses are mainly caused by congestion. In wireless networks, packets can be lost due to transmission errors and for other reasons that are independent of congestion. TCP already detects segment losses to ensure a reliable delivery. The TCP congestion control scheme distinguishes between two types of congestion :
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../../protocols/email.rst:50
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protocols, that allow hosts and servers to exchange email messages
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../../protocols/ethernet.rst:49
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The fourth part of the Ethernet frame is the payload. The minimum length of the payload is 46 bytes to ensure a minimum frame size, including the header of 512 bits. The Ethernet payload cannot be longer than 1500 bytes. This size was found reasonable when the first Ethernet specification was written. At that time, Xerox had been using its experimental 3 Mbps Ethernet that offered 554 bytes of payload and :rfc:`1122` required a minimum MTU of 572 bytes for IPv4. 1500 bytes was large enough to support these needs without forcing the network adapters to contain overly large memories. Furthermore, simulations and measurement studies performed in Ethernet networks revealed that CSMA/CD was able to achieve a very high utilization. This is illustrated in the figure below based on [SH1980]_, which shows the channel utilization achieved in Ethernet networks containing different numbers of hosts that are sending frames of different sizes.
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../../protocols/http.rst:16
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`FTP` was very popular in the 1990s and early 2000s, but today it has mostly been superseded by more recent protocols. Authenticated access to files is mainly done by using the Secure Shell (ssh_) protocol defined in :rfc:`4251` and supported by clients such as scp_ or sftp_. Nowadays, anonymous access is mainly provided by web protocols.
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../../protocols/http2.rst:50
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These reverse proxies can also be used to spread the load among different servers. In the above example, consider that a server needs 10 milliseconds to process each request and that it must handle them sequentially. Such a server cannot support more than 100 requests per second. If the service becomes popular, then the content provider will need to deploy several servers. These servers could serve the same reverse proxy.
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../../protocols/ipv6.rst:65
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A local area network
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../../protocols/ppp.rst:15
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While SLIP was implemented and used in some environments, it had several limitations discussed in :rfc:`1055`. The `Point-to-Point Protocol` (PPP) was designed shortly after and is specified in :rfc:`1548`. PPP aims to support IP and other network layer protocols over various types of serial lines. PPP is in fact a family of three protocols that are used together :
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../../protocols/ppp.rst:18
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The `Link Control Protocol` that is used to negotiate options and authenticate the session by using username and password or other types of credentials
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../../protocols/routing.rst:21
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The second class of routing protocols are the `interdomain routing protocols` (sometimes also called the exterior gateway protocols or :term:`EGP`). The objective of an interdomain routing protocol is to distribute routing information between domains. For scalability reasons, an interdomain routing protocol must distribute aggregated routing information and considers each domain as a black box.
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../../protocols/rpc.rst:14
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The callee accesses the parameters and performs the requested computation
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