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../../exercises/ipv6.rst:232
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Can you configure the forwarding tables so that the following paths are used by packets sent by host ``A`` to reach one of the four addresses of router ``R4``?
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../../exercises/routing-protocols.rst:359
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the requests
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../../exercises/tcp-2.rst:147
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Let us first explore how a TCP connection can be established. In the previous script, we have injected the segments that a client would send to a server. We can also use the Linux stack as a client and inject the segments that a server would return. Such a client process would first create its :manpage:`socket`` and then issue the :manpage:`connect` system call. At this point, the stack sends a ``SYN`` segment. To simplify the scripts, we have configured the stack to use a ``MSS`` of 1000 bytes and disabled the TCP extensions (the details of this configuration may be found at the beginning of the script). The server replies with a ``SYN+ACK`` and the stack sends acknowledges it to finish the three-way-handshake.
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../../protocols/bgp.rst:86
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The figure below provides a simple example of import and export filters for two domains in a simple internetwork. In RPSL, the keyword `ANY` is used to replace any route from any domain. It is typically used by a provider to indicate that it announces all its routes to a customer over a `provider->customer` relationship. This is the case for `AS4`'s export policy. The example below clearly shows the difference between a `provider->customer` and a `shared-cost` peering relationship. `AS4`'s export filter indicates that it announces only its internal routes (`AS4`) and the routes learned from its clients (`AS7`) over its `shared-cost` peering with `AS3`, while it advertises all the routes that it uses (including the routes learned from `AS3`) to `AS7`.
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../../protocols/congestion.rst:168
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The `CWR` bit of the TCP header provides some form of acknowledgment for the `ECE` bit. When a TCP receiver detects a packet marked with the `CE` bit, it sets the `ECE` bit in all segments that it returns to the sender. Upon reception of an acknowledgment with the `ECE` bit set, the sender reduces its congestion window to reflect a mild congestion and sets the `CWR` bit. This bit remains set as long as the segments received contained the `ECE` bit set. A sender should only react once per round-trip-time to marked packets.
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../../protocols/dnssec.rst:302
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In this domain, the DNSSEC server adds three `NSEC` records. A `RRSIG` signature is also computed for each of these records.
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../../protocols/email.rst:130
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The figure below shows the header lines of one email message. The message originated at a host named `wira.firstpr.com.au` and was received by `smtp3.sgsi.ucl.ac.be`. The `Received:` lines have been wrapped for readability.
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../../protocols/ethernet.rst:169
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Comments
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../../protocols/http.rst:117
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a `header`, that is used by the client to specify optional parameters for the request. An empty line is used to mark the end of the header
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../../protocols/http2.rst:193
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With HTTP/2.0 frames, the server could send the first 1250 bytes of the long object during 10 milliseconds, then send a second frame that contains the short object during one millisecond and later send a longer frame that contains the remaining 11250 bytes of the long object. In this case, the client has received the short object after 10 milliseconds. Given the HTTP/2.0 streams, the transmission of long web objects does not anymore blocks the transmission of shorter ones.
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../../protocols/ipv6.rst:113
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``abcd:ef01:2345:6789:abcd:ef01:2345:6789``
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../../protocols/ethernet.rst:81
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The Ethernet frame format shown above is specified in [DIX]_. This is the format used to send both IPv4 :rfc:`894` and IPv6 packets :rfc:`2464`. After the publication of [DIX]_, the Institute of Electrical and Electronic Engineers (IEEE) began to standardize several Local Area Network technologies. IEEE worked on several LAN technologies, starting with Ethernet, Token Ring and Token Bus. These three technologies were completely different, but they all agreed to use the 48 bits MAC addresses specified initially for Ethernet [IEEE802]_ . While developing its Ethernet standard [IEEE802.3]_, the IEEE 802.3 working group was confronted with a problem. Ethernet mandated a minimum payload size of 46 bytes, while some companies were looking for a LAN technology that could transparently transport short frames containing only a few bytes of payload. Such a frame can be sent by an Ethernet host by padding it to ensure that the payload is at least 46 bytes long. However since the Ethernet header [DIX]_ does not contain a length field, it is impossible for the receiver to determine how many useful bytes were placed inside the payload field. To solve this problem, the IEEE decided to replace the `Type` field of the Ethernet [DIX]_ header with a length field [#ftypelen]_. This `Length` field contains the number of useful bytes in the frame payload. The payload must still contain at least 46 bytes, but padding bytes are added by the sender and removed by the receiver. In order to add the `Length` field without significantly changing the frame format, IEEE had to remove the `Type` field. Without this field, it is impossible for a receiving host to identify the type of network layer packet inside a received frame. To solve this new problem, IEEE developed a completely new sublayer called the Logical Link Control [IEEE802.2]_. Several protocols were defined in this sublayer. One of them provided a slightly different version of the `Type` field of the original Ethernet frame format. Another contained acknowledgments and retransmissions to provide a reliable service... In practice, [IEEE802.2]_ is never used to support IP in Ethernet networks. The figure below shows the official [IEEE802.3]_ frame format.
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../../protocols/routing.rst:86
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Inside each non-backbone area, routers distribute the topology of the area by exchanging link state packets with the other routers in the area. The internal routers do not know the topology of other areas, but each router knows how to reach the backbone area. Inside an area, the routers only exchange link-state packets for all destinations that are reachable inside the area. In OSPF, the inter-area routing is done by exchanging distance vectors. This is illustrated by the network topology shown below.
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../../protocols/rpc.rst:105
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`id`: an identifier chosen by the caller
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../../protocols/ssh.rst:218
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At this point, all the messages sent over the TCP connection will be encrypted with the negotiated keys. The ``ssh`` protocol uses messages that are encoded according to the Binary Packet Protocol defined in :rfc:`4253`. Each of these messages contains the following information :
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../../protocols/tcp.rst:55
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the `checksum` field contains the value of the Internet checksum computed over the entire TCP segment and a pseudo-header as with UDP
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../../protocols/tls.rst:93
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The TLS handshake
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../../protocols/udp.rst:92
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A discussion of the ephemeral port ranges used by different TCP/UDP implementations may be found in http://www.ncftp.com/ncftpd/doc/misc/ephemeral_ports.html
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../../protocols/wifi.rst:26
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802.11n
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../../bibliography.rst:94
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Jacobson, V., `Congestion avoidance and control <http://doi.acm.org/10.1145/52324.52356>`_. In Symposium Proceedings on Communications Architectures and Protocols (Stanford, California, United States, August 16 - 18, 1988). V. Cerf, Ed. SIGCOMM '88. ACM, New York, NY, 314-329.
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