Exit Zen
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../../protocols/bgp.rst:488
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A link is said to be flapping if it switches several times between an operational state and a disabled state within a short period of time. A router attached to such a link would need to frequently send routing messages.
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../../protocols/email.rst:256
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d
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../../protocols/ipv6.rst:439
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the 32-bit `Identification` field indicates to which original packet a fragment belongs. When a host sends fragmented packets, it should ensure that it does not reuse the same `identification` field for packets sent to the same destination during a period of `MSL` seconds. This is easier with the 32 bits `identification` used in the IPv6 fragmentation header, than with the 16 bits `identification` field of the IPv4 header.
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../../protocols/wifi.rst:19
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Range (m) indoor/outdoor
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../../protocols/tcp.rst:411
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Jacobson's algorithm uses two state variables, `srtt` the smoothed `rtt` and `rttvar` the estimation of the variance of the `rtt` and two parameters : :math:`\alpha` and :math:`\beta`. When a TCP connection starts, the first `rto` is set to `3` seconds. When a first estimation of the `rtt` is available, the `srtt`, `rttvar` and `rto` are computed as follows :
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../../principles/reliability.rst:446
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Received bits
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../../principles/transport.rst:759
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In the datalink layer, the sliding window has usually a fixed size which depends on the amount of buffers allocated to the datalink layer entity. Such a datalink layer entity usually serves one or a few network layer entities. In the transport layer, the situation is different. A single transport layer entity serves a large and varying number of application processes. Each transport layer entity manages a pool of buffers that needs to be shared between all these processes. Transport entity are usually implemented inside the operating system kernel and shares memory with other parts of the system. Furthermore, a transport layer entity must support several (possibly hundreds or thousands) of transport connections at the same time. This implies that the memory which can be used to support the sending or the receiving buffer of a transport connection may change during the lifetime of the connection [#fautotune]_ . Thus, a transport protocol must allow the sender and the receiver to adjust their window sizes.
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../../principles/sharing.rst:674
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After having transmitted its data frame, the station must remain in `Transmit` mode until it has received the last bit of its own data frame. This ensures that the bits sent by a station do not remain in the network forever. A data frame sent by a station in a Token Ring network passes in front of all stations attached to the network. Each station can detect the data frame and analyze the destination address to possibly capture the frame.
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../../protocols/bgp.rst:490
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Researchers such as [MUF+2007]_ have shown that modeling the Internet topology at the AS-level requires more than the `shared-cost` and `customer->provider` peering relationships. However, there is no publicly available model that goes beyond these classical peering relationships.
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../../protocols/email.rst:256
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../../protocols/ipv6.rst:445
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Some IPv6 implementations send the fragments of a packet in increasing fragment offset order, starting from the first fragment. Others send the fragments in reverse order, starting from the last fragment. The latter solution can be advantageous for the host that needs to reassemble the fragments, as it can easily allocate the buffer required to reassemble all fragments of the packet upon reception of the last fragment. When a host receives the first fragment of an IPv6 packet, it cannot know a priori the length of the entire IPv6 packet.
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../../protocols/wifi.rst:22
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802.11
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../../protocols/tcp.rst:424
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Then, when other rtt measurements are collected, `srtt` and `rttvar` are updated as follows :
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../../glossary.rst:258
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The Post Office Protocol (POP), defined :rfc:`1939`, is an application-level protocol that allows a client to download email messages stored on a server.
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../../principles/dv.rst:90
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To deal with link and router failures, routers use the timestamp stored in their routing table. As all routers send their distance vector every `N` seconds, the timestamp of each route should be regularly refreshed. Thus no route should have a timestamp older than `N` seconds, unless the route is not reachable anymore. In practice, to cope with the possible loss of a distance vector due to transmission errors, routers check the timestamp of the routes stored in their routing table every `N` seconds and remove the routes that are older than :math:`3 \times N` seconds.
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../../principles/reliability.rst:446
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Decoded bit
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../../principles/transport.rst:761
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To deal with this issue, transport protocols allow the receiver to advertise the current size of its receiving window in all the acknowledgments that it sends. The receiving window advertised by the receiver bounds the size of the sending buffer used by the sender. In practice, the sender maintains two state variables : `swin`, the size of its sending window (that may be adjusted by the system) and `rwin`, the size of the receiving window advertised by the receiver. At any time, the number of unacknowledged segments cannot be larger than :math:`\min(swin,rwin)` [#facklost]_ . The utilization of dynamic windows is illustrated in the figure below.
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../../principles/sharing.rst:682
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The text above describes the basic operation of a Token Ring network when all stations work correctly. Unfortunately, a real Token Ring network must be able to handle various types of anomalies and this increases the complexity of Token Ring stations. We briefly list the problems and outline their solutions below. A detailed description of the operation of Token Ring stations may be found in [IEEE802.5]_. The first problem is when all the stations attached to the network start. One of them must bootstrap the network by sending the first token. For this, all stations implement a distributed election mechanism that is used to select the `Monitor`. Any station can become a `Monitor`. The `Monitor` manages the Token Ring network and ensures that it operates correctly. Its first role is to introduce a delay of 24 bit transmission times to ensure that the token can travel smoothly on the ring. Second, the `Monitor` sends the first token on the ring. It must also verify that the token passes regularly. According to the Token Ring standard [IEEE802.5]_, a station cannot retain the token to transmit data frames for a duration longer than the `Token Holding Time` (THT) (slightly less than 10 milliseconds). On a network containing `N` stations, the `Monitor` must receive the token at least every :math:`N \times THT` seconds. If the `Monitor` does not receive a token during such a period, it cuts the ring for some time and then re-initializes the ring and sends a token.
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../../protocols/bgp.rst:492
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BGP data is often collected by establishing BGP sessions between Unix hosts running a BGP daemon and BGP routers in different ASes. The Unix hosts stores all BGP messages received and regular dumps of its BGP routing table. See http://www.routeviews.org, http://www.ripe.net/ris, http://bgp.potaroo.net or http://irl.cs.ucla.edu/topology/.
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../../protocols/email.rst:256
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u
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