Exit Zen
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../../principles/transport.rst:165
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In practice, an `unreliable connectionless service` will usually deliver a large fraction of the SDUs. However, since the delivery of SDUs is not guaranteed, the user must be able to recover from the loss of any SDU.
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../../principles/security.rst:571
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A better approach would be to authenticate Alice without storing her password in clear on Bob's computer. For this, Alice computes a `hash chain` as proposed by Lamport in [Lamport1981]_. A hash chain is a sequence of applications of a hash function (`H`) on an input string. If Alice's password is `P`, then her 10 steps hash chain is : :math:`H(H(H(H(H(H(H(H(H(H(P))))))))))`. The result of this hash chain will be stored on Bob's computer together with the value `10`. This number is the maximum number of remaining authentications for Alice on Bob's computer. To authenticate Alice, Bob sends the remaining number of authentications, i.e. `10` in this example. Since Alice knows her password, `P`, she can compute :math:`H^9(P)=H(H(H(H(H(H(H(H(H(P)))))))))` and send this information to Bob. Bob computes the hash of the value received from Alice (:math:`H(H^9(P))`) and verifies that this value is equal to the value stored in his database. It then decrements the number of authorized authentications and stores :math:`H^9(P)` in his database. Bob is now ready for the next authentication of Alice. When the number of authorized authentications reaches zero, the hash chain needs to be reinitialized. If Eve captures :math:`(H^n(P))`, she cannot use it to authenticate herself as Alice on Bob's computer because Bob will have decremented its number of authorized authentications. Furthermore, given that hash functions are not invertible, Eve cannot compute :math:`H^{n-1}(P)` from :math:`H^{n}(P)`.
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../../exercises/ipv6.rst:527
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Configuring IPv6 Networks
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../../exercises/routing-protocols.rst:812
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We can now observe the BGP-Loc-RIB of the router with the ``show bgp ipv6 command`` command.
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../../exercises/tcp-2.rst:688
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How long does it take for the sender to deliver 3 KBytes to the receiver ?
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../../protocols/bgp.rst:166
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When a BGP session starts, the routers first exchange `OPEN` messages to negotiate the options that apply throughout the entire session. Then, each router extracts from its FIB the routes to be advertised to the peer. It is important to note that, for each known destination prefix, a BGP router can only advertise to a peer the route that it has itself installed inside its `FIB`. The routes that are advertised to a peer must pass the peer's `export filter`. The `export filter` is a set of rules that define which routes can be advertised over the corresponding session, possibly after having modified some of its attributes. One `export filter` is associated to each BGP session. For example, on a `shared-cost peering`, the `export filter` only selects the internal routes and the routes that have been learned from a `customer`. The pseudo-code below shows the initialization of a BGP session.
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../../protocols/congestion.rst:238
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In enterprise networks or datacenters, the situation is different since a single company typically controls all the sources and all the routers. In such networks it is possible to ensure that all hosts and routers have been upgraded before turning on ECN on the routers.
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../../protocols/email.rst:232
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../../protocols/ethernet.rst:207
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Ethernet Switches
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../../protocols/http.rst:188
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All status codes starting with digit `3` indicate that the requested document is no longer available on the server. `301 Moved Permanently` indicates that the requested document is no longer available on this server. A `Location:` header containing the new URI of the requested document is inserted in the HTTP response. `304 Not Modified` is used in response to an HTTP request containing the `If-Modified-Since:` header. This status line is used by the server if the document stored on the server is not more recent than the date indicated in the `If-Modified-Since:` header.
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../../protocols/ipv6.rst:181
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``/64`` for a single user (e.g. a home user connected via ADSL)
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../../protocols/ethernet.rst:177
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1000Base-CX
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../../protocols/routing.rst:170
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See http://bgp.potaroo.net/index-as.html for reports on the evolution of the number of Autonomous Systems over time.
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../../protocols/tcp.rst:192
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When a TCP entity opens a TCP connection, it creates a Transmission Control Block (:term:`TCB`). The TCB contains the entire state that is maintained by the TCP entity for each TCP connection. During connection establishment, the TCB contains the local IP address, the remote IP address, the local port number, the remote port number, the current local sequence number and the last sequence number received from the remote entity. Until the mid 1990s, TCP implementations had a limit on the number of TCP connections that could be in the `SYN RCVD` state at a given time. Many implementations set this limit to about 100 TCBs. This limit was considered sufficient even for heavily load http servers given the small delay between the reception of a `SYN` segment and the reception of the `ACK` segment that terminates the establishment of the TCP connection. When the limit of 100 TCBs in the `SYN Rcvd` state is reached, the TCP entity discards all received TCP `SYN` segments that do not correspond to an existing TCB.
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../../protocols/tls.rst:294
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The server also sends a ``ChangeCipherSpec`` message followed by a ``Finished`` message.
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../../protocols/wifi.rst:157
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Footnotes
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../../bibliography.rst:335
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Stevens, R., `UNIX Network Programming, Volume 1, Second Edition: Networking APIs: Sockets and XTI <http://books.google.com/books?id=ptSC4LpwGA0C>`_, Prentice Hall, 1998
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../../glossary.rst:186
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HTTP
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../../principles/network.rst:251
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With the received `record route`, `B` can send a `data packet` to `A`. For this, it simply reverses the chosen `record route`. However, we still need to communicate the chosen path to `A`. This can be done by putting the `record route` inside a control packet which is sent back to `A` over the reverse path. An alternative is to simply send a `data packet` back to `A`. This packet will travel back to `A`. To allow `A` to inspect the entire path followed by the `data packet`, its `source route` must contain all intermediate routers when it is received by `A`. This can be achieved by encoding the `source route` using a data structure that contains an index and the ordered list of node addresses. The index always points to the next address in the `source route`. It is initialized at `0` when a packet is created and incremented by each intermediate node.
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../../principles/reliability.rst:222
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01111110000100100100100100100001101111110
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