Exit Zen
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../../principles/transport.rst:775
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Risk of deadlock with dynamic windows
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../../principles/sharing.rst:690
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Most networks contain links having different bandwidth. Some hosts can use low bandwidth wireless networks. Some servers are attached via 10 Gbps interfaces and inter-router links may vary from a few tens of kilobits per second up to hundred Gbps. Despite these huge differences in performance, any host should be able to efficiently exchange segments with a high-end server.
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../../protocols/email.rst:258
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../../protocols/ipv6.rst:490
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In the above pseudocode, we maintain a single 32 bits counter that is incremented for each packet that needs to be fragmented. Other implementations to compute the packet identification are possible. :rfc:`2460` only requires that two fragmented packets that are sent within the MSL between the same pair of hosts have different identifications.
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../../protocols/wifi.rst:22
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../../protocols/tcp.rst:432
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The proposed values for the parameters are :math:`\alpha=\frac{1}{8}` and :math:`\beta=\frac{1}{4}`. This allows a TCP implementation, implemented in the kernel, to perform the `rtt` computation by using shift operations instead of the more costly floating point operations [Jacobson1988]_. The figure below illustrates the computation of the `rto` upon `rtt` changes.
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../../glossary.rst:249
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A server that implements the DNS protocol and can resolve queries. A resolver usually serves a set of clients (e.g. all hosts in campus or all clients of a given ISP). It sends DNS queries to nameservers everywhere on behalf of its clients and stores the received answers in its cache. A resolver must know the IP addresses of the root nameservers.
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../../principles/dv.rst:97
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`D` sends its distance vector :math:`[D=0,B=\infty,A=1,C=2,E=1]` to `A` and `E`. `A` recovers routes towards `C` and `E` via `D`.
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../../principles/reliability.rst:464
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a `payload` that contains the user data
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../../principles/transport.rst:780
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To solve this problem, transport protocols rely on a special timer : the `persistence timer`. This timer is started by the sender whenever it receives an acknowledgment advertising a receive window set to `0`. When the timer expires, the sender retransmits an old segment in order to force the receiver to send a new acknowledgment, and hence send the current receive window size.
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../../principles/sharing.rst:694
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To understand this problem better, let us consider the scenario shown in the figure below, where a server (`A`) attached to a `10 Mbps` link needs to reliably transfer segments to another computer (`C`) through a path that contains a `2 Mbps` link.
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../../protocols/email.rst:258
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N
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../../protocols/ipv6.rst:492
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The fragments of an IPv6 packet may arrive at the destination in any order, as each fragment is forwarded independently in the network and may follow different paths. Furthermore, some fragments may be lost and never reach the destination.
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../../protocols/wifi.rst:23
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802.11a
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../../protocols/tcp.rst:439
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Example computation of the `rto`
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../../glossary.rst:138
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RIP
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../../principles/dv.rst:98
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`B` sends its distance vector :math:`[B=0,A=\infty,C=1,D=2,E=1]` to `E` and `C`. `C` learns that there is no route anymore to reach `A` via `B`.
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../../principles/reliability.rst:466
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Some headers also include a `length` field, which indicates the total length of the frame or the length of the payload.
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../../principles/transport.rst:782
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To conclude our description of the basic mechanisms found in transport protocols, we still need to discuss the impact of segments arriving in the wrong order. If two consecutive segments are reordered, the receiver relies on their sequence numbers to reorder them in its receive buffer. Unfortunately, as transport protocols reuse the same sequence number for different segments, if a segment is delayed for a prolonged period of time, it might still be accepted by the receiver. This is illustrated in the figure below where segment `D(1,b)` is delayed.
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../../protocols/email.rst:258
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