Exit Zen
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../../glossary.rst:304
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inverse query
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../../principles/network.rst:345
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sending a control packet back to the source if a packet is received by a router that does not have a valid entry in its forwarding table
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../../principles/reliability.rst:260
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`DLE STX` **1** **2** **3** **4** `DLE ETX`
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../../principles/transport.rst:409
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An abrupt connection release can also be triggered by one of the users. If a user needs, for any reason, to terminate a connection quickly, it can issue a `Disconnect.request` primitive and to request an abrupt release. The service provider will process the request, stop the two data streams and deliver the `Disconnect.indication` primitive to the remote user as soon as possible. As illustrated in the figure below, this abrupt connection release may cause losses of SDUs.
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../../principles/security.rst:913
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Key exchange
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../../exercises/ipv6.rst:732
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Some of the standard mininet commands assume the utilisation of IPv4 and do not have a direct IPv6 equivalent. Here are some useful commands.
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../../exercises/routing-protocols.rst:1128
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What are the BGP messages that will be exchanged when the link between ``AS1`` and ``AS5`` fails ? How does this affect the reachability of the different hosts ?
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../../protocols/bgp.rst:311
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The first BGP attribute that is used to rank BGP routes is the `local-preference` (local-pref) attribute. This attribute is an unsigned integer that is attached to each BGP route received over an eBGP session by the associated import filter.
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../../protocols/email.rst:238
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../../protocols/ethernet.rst:350
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In addition to the `identifier` discussed above, the network administrator can also configure a `cost` to be associated to each switch port. Usually, the `cost` of a port depends on its bandwidth and the [IEEE802.1d]_ standard recommends the values below. Of course, the network administrator may choose other values. We will use the notation `cost[p]` to indicate the cost associated to port `p` in this section.
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../../protocols/http.rst:443
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Footnotes
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../../protocols/ipv6.rst:321
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IPv6 packet format
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../../protocols/ethernet.rst:303
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When all switches boot, their `MAC address table` is empty. Assume that host `A` sends a frame towards host `C`. Upon reception of this frame, switch1 updates its `MAC address table` to remember that address `A` is reachable via its West port. As there is no entry for address `C` in switch1's `MAC address table`, the frame is forwarded to both switch2 and switch3. When switch2 receives the frame, its updates its `MAC address table` for address `A` and forwards the frame to host `C` as well as to switch3. switch3 has thus received two copies of the same frame. As switch3 does not know how to reach the destination address, it forwards the frame received from switch1 to switch2 and the frame received from switch2 to switch1... The single frame sent by host `A` will be continuously duplicated by the switches until their `MAC address table` contains an entry for address `C`. Quickly, all the available link bandwidth will be used to forward all the copies of this frame. As Ethernet does not contain any `TTL` or `HopLimit`, this loop will never stop.
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../../protocols/tcp.rst:250
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`acknowledgment number`. TCP uses cumulative positive acknowledgments. Each TCP segment contains the `sequence number` of the next byte that the sender of the acknowledgment expects to receive from the remote host. In theory, the `acknowledgment number` is only valid if the `ACK` flag of the TCP header is set. In practice, almost all [#fackflag]_ TCP segments have their `ACK` flag set.
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../../protocols/tls.rst:406
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reduce the latency of TLS
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../../glossary.rst:306
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For DNS servers and resolvers, an inverse query is a query for the domain name that corresponds to a given IP address.
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../../principles/network.rst:346
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sending a control packet back to the source if a router detects that a packet is looping inside the network
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../../principles/reliability.rst:261
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**1** **2** **3** **DLE** **STX** **4**
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../../principles/transport.rst:447
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To ensure a reliable delivery of the SDUs sent by each user over a connection, we need to consider the two streams that compose a connection as independent. A user should be able to release the stream that it uses to send SDUs once it has sent all the SDUs that it planned to send over this connection, but still continue to receive SDUs over the opposite stream. This `graceful` connection release is usually performed as shown in the figure below. One user issues a `Disconnect.request` primitive to its provider once it has issued all its `Data.request` primitives. The service provider will wait until all `Data.indication` primitives have been delivered to the receiving user before issuing the `Disconnnect.indication` primitive. This primitive informs the receiving user that it will no longer receive SDUs over this connection, but it is still able to issue `Data.request` primitives on the stream in the opposite direction. Once the user has issued all of its `Data.request` primitives, it issues a `Disconnnect.request` primitive to request the termination of the remaining stream. The service provider will process the request and deliver the corresponding `Disconnect.indication` to the other user once it has delivered all the pending `Data.indication` primitives. At this point, all data has been delivered, the two streams have been released successfully and the connection is completely closed.
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../../principles/sharing.rst:338
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[Abramson1970]_ analyzed the performance of ALOHANet under particular assumptions and found that ALOHANet worked well when the channel was lightly loaded. In this case, the frames are rarely retransmitted and the `channel traffic`, i.e. the total number of (correct and retransmitted) frames transmitted per unit of time is close to the `channel utilization`, i.e. the number of correctly transmitted frames per unit of time. Unfortunately, the analysis also reveals that the `channel utilization` reaches its maximum at :math:`\frac{1}{2 \times e}=0.186` times the channel bandwidth. At higher utilization, ALOHANet becomes unstable and the network collapses due to collided retransmissions.
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