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../../principles/network.rst:102
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With the datagram organization, routers use `hop-by-hop forwarding`. This means that when a router receives a packet that is not destined to itself, it looks up the destination address of the packet in its `forwarding table`. A `forwarding table` is a data structure that maps each destination address (or set of destination addresses) to the outgoing interface over which a packet destined to this address must be forwarded to reach its final destination. The router consults its forwarding table to forward each packet that it handles.
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../../principles/reliability.rst:66
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On the receiver side :
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../../principles/transport.rst:58
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Let us first discuss the syntactical rules. We will later explain how the information flow can be organized by analyzing real networked applications.
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../../principles/security.rst:316
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Various secret key cryptographic functions have been proposed, implemented and deployed. The most popular ones are :
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../../exercises/dns.rst:75
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Imagine an attacker who is able to send forged DNS replies to, for example, associate `www.bigbank.com` to his own IP address. How could he attack a DNS implementation that
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../../exercises/ipv6.rst:227
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router ``R1`` uses address ``2001:db8:1341:1::1`` on its West interface, address ``2001:db8:1341:12::1`` on its East interface, address ``2001:db8:1341:14::1`` on its South-East interface and address ``2001:db8:1341:13::1`` on its South interface
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../../exercises/lan.rst:293
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:manpage:`brctl(8)` also maintains a MAC address table that contains the Ethernet addresses that have been learned on each switch port.
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../../exercises/routing-policies.rst:213
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An ICMPv6 error message includes in its message body the beginning of the IPv6 packet that triggered this error. How many bytes of the original packet must be returned to allow the host to recover the original source and destination addresses and source and destination ports of the packet that caused the error ?
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../../exercises/routing-protocols.rst:336
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As RIP messages are exchanged using UDP on port 521, we filter this port in the tcpdump_ trace. RIPng distributes the routes and our two hosts can exchange packets. The entire script is available from :download:`/exercises/ipmininet_scripts/ripng.py`.
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../../exercises/tcp-2.rst:142
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The complete packetdrill_ script is available from :download:`/exercises/packetdrill_scripts/connect.pkt`.
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../../protocols/bgp.rst:80
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the `ranking` algorithm that is used to select the best route among all the routes that the domain has received towards the same destination prefix
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../../protocols/congestion.rst:124
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If TCP acknowledgments are overloaded to carry the `ECE` bit, the situation is different. Consider the example shown in the figure below. A client sends packets to a server through a router. In the example below, the first packet is marked. The server returns an acknowledgment with the `ECE` bit set. Unfortunately, this acknowledgment is lost and never reaches the client. Shortly after, the server sends a data segment that also carries a cumulative acknowledgment. This acknowledgment confirms the reception of the data to the client, but it did not receive the congestion information through the `ECE` bit.
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../../protocols/dnssec.rst:277
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The simplest way to allow a DNSSEC server to return signed negative responses would be for the server to return a signed response that contains the received query and some information indicating the error. The client could then easily check the validity of the negative response. Unfortunately, this would force the DNSSEC server to generate signatures in real time. This implies that the private key must be stored in the server memory, which leads to risks if an attacker can take control of the server. Furthermore, those signatures are computationally complex and a simple denial of service attack would be to send invalid queries to a DNSSEC server.
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../../protocols/email.rst:127
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the `In-reply-to:` header line is used when a message was created in reply to a previous message. In this case, the end of the `In-reply-to:` line contains the identifier of the original message.
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../../protocols/ethernet.rst:164
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The evolution of Ethernet did not stop. In 1998, the IEEE published a first standard to provide Gigabit Ethernet over optical fibers. Several other types of physical layers were added afterwards. The `10 Gigabit Ethernet <http://en.wikipedia.org/wiki/10_gigabit_Ethernet>`_ standard appeared in 2002. Work is ongoing to develop `standards <http://www.ieee802.org/3/ba/public/index.html>`_ for 40 Gigabit and 100 Gigabit Ethernet and some are thinking about `Terabit Ethernet <http://www.networkworld.com/news/2009/042009-terabit-ethernet.html>`_. The table below lists the main Ethernet standards. A more detailed list may be found at http://en.wikipedia.org/wiki/Ethernet_physical_layer.
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../../protocols/http.rst:114
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The third component of the `world wide web` is the HyperText Transfer Protocol (HTTP). HTTP is a text-based protocol like SMTP. The client sends a request and the server returns a response. HTTP runs above the bytestream service and HTTP servers listen by default on port `80`. The design of HTTP has largely been inspired by the Internet email protocols. Each HTTP request contains three parts :
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../../protocols/http2.rst:165
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This multiplexing capability is probably the most important feature of HTTP/2.0 from a performance viewpoint. To understand its benefits, let us consider a client that retrieves two web objects over a 1 Mbps connection. The two requests are sent together by the client. The first object is 125 bytes long, while the second is 12500 bytes long. In this case, the server will first return the first object as a single frame and the second will be sent in the subsequent frame.
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../../protocols/ipv6.rst:109
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Textual representation of IPv6 addresses
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../../protocols/ethernet.rst:70
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Where should the CRC be located in a frame ?
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../../protocols/routing.rst:78
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For example, the network shown in the figure below has been divided into three areas : `area 0`, containing routers `RA`, `RB`, `RC` and `RD`, `area 1`, containing routers `R1`, `R3`, `R4`, `R5` and `RA`, and `area 2` containing `R7`, `R8`, `R9`, `R10`, `RB` and `RC`. OSPF areas are identified by a 32 bit integer, which is sometimes represented as an IP address. Among the OSPF areas, `area 0`, also called the `backbone area`, has a special role. The backbone area groups all the area border routers (routers `RA`, `RB` and `RC` in the figure below) and the routers that are directly connected to the backbone routers but do not belong to another area (router `RD` in the figure below). An important restriction imposed by OSPF is that the path between two routers that belong to two different areas (e.g. `R1` and `R8` in the figure below) must pass through the backbone area.
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