Exit Zen
196
../../protocols/ipv6.rst:692
English
The next step is to connect the LAN to the Internet. For this, a router is attached to the LAN.
0/950 · 95
196
../../protocols/tcp.rst:653
English
In theory, a TCP implementation could store the timestamp of each data segment transmitted and compute a new estimate for the round-trip-time upon reception of the corresponding acknowledgment. However, using such frequent measurements introduces a lot of noise in practice and many implementations still measure the round-trip-time once per round-trip-time by recording the transmission time of one segment at a time :rfc:`2988`
0/4290 · 429
197
../../glossary.rst:45
English
W3C
0/100 · 3
197
../../principles/linkstate.rst:116
English
When a router has failed, its LSP must be removed from the LSDB of all routers [#foverload]_. This can be done by using the `age` field that is included in each LSP. The `age` field is used to bound the maximum lifetime of a link state packet in the network. When a router generates a LSP, it sets its lifetime (usually measured in seconds) in the `age` field. All routers regularly decrement the `age` of the LSPs in their LSDB and a LSP is discarded once its `age` reaches `0`. Thanks to the `age` field, the LSP from a failed router does not remain in the LSDBs forever.
0/5730 · 573
197
../../principles/reliability.rst:811
English
In the figure above, when the sender receives `C(OK,0,[2])`, it knows that all frames up to and including `D(0,...)` have been correctly received. It also knows that frame `D(2,...)` has been received and can cancel the retransmission timer associated to this frame. However, this frame should not be removed from the sending buffer before the reception of a cumulative acknowledgment (`C(OK,2)` in the figure above) that covers this frame.
0/4400 · 440
197
../../principles/sharing.rst:1335
English
For example, the measurements performed in the Sprint network in 2004 reported more than 10k active TCP connections on a link, see https://research.sprintlabs.com/packstat/packetoverview.php. More recent information about backbone links may be obtained from caida_ 's real-time measurements, see e.g. http://www.caida.org/data/realtime/passive/
0/3450 · 345
197
../../protocols/email.rst:358
English
The SMTP responses are defined by the BNF shown in the figure below.
0/680 · 68
197
../../protocols/ipv6.rst:711
English
Assume that the LAN containing the two hosts and the router is assigned prefix ``2001:db8:1234:5678/64``. A first solution to configure the IPv6 addresses in this network is to assign them manually. A possible assignment is :
0/2250 · 225
197
../../protocols/tcp.rst:655
English
Some security experts have raised concerns that using the real-time clock to set the `TSval` in the timestamp option can leak information such as the system's up-time. Solutions proposed to solve this problem may be found in [CNPI09]_
0/2340 · 234
198
../../glossary.rst:47
English
The world wide web consortium was created to standardize the protocols and mechanisms used in the world wide web. It is thus focused on a subset of the application layer. See https://www.w3.org
0/1930 · 193
198
../../principles/linkstate.rst:118
English
To compute its forwarding table, each router computes the spanning tree rooted at itself by using Dijkstra's shortest path algorithm [Dijkstra1959]_. The forwarding table can be derived automatically from the spanning as shown in the figure below.
0/2470 · 247
198
../../protocols/email.rst:363
English
BNF specification of the SMTP responses
0/390 · 39
198
../../protocols/ipv6.rst:713
English
``2001:db8:1234:5678::1`` is assigned to ``router``
0/510 · 51
198
../../protocols/tcp.rst:657
English
As a TCP client often establishes several parallel or successive connections with the same server, :rfc:`2140` has proposed to reuse for a new connection some information that was collected in the TCB of a previous connection, such as the measured rtt. However, this solution has not been widely implemented.
0/3080 · 308
199
../../glossary.rst:33
English
WAN
0/100 · 3
199
../../principles/reliability.rst:817
English
A reliable protocol that uses `n` bits to encode its sequence number can send up to :math:`2^n` successive frames. However, to ensure a reliable delivery of the frames, `go-back-n` and `selective repeat` cannot use a sending window of :math:`2^n` frames. Consider first `go-back-n` and assume that a sender sends :math:`2^n` frames. These frames are received in-sequence by the destination, but all the returned acknowledgments are lost. The sender will retransmit all frames. These frames will all be accepted by the receiver and delivered a second time to the user. It is easy to see that this problem can be avoided if the maximum size of the sending window is :math:`{2^n}-1` frames. A similar problem occurs with `selective repeat`. However, as the receiver accepts out-of-sequence frames, a sending window of :math:`{2^n}-1` frames is not sufficient to ensure a reliable delivery. It can be easily shown that to avoid this problem, a `selective repeat` sender cannot use a window that is larger than :math:`\frac{2^n}{2}` frames.
0/10350 · 1035
199
../../protocols/email.rst:366
English
SMTP servers use structured reply codes containing three digits and an optional comment. The first digit of the reply code indicates whether the command was successful or not. A reply code of `2xy` indicates that the command has been accepted. A reply code of `3xy` indicates that the command has been accepted, but additional information from the client is expected. A reply code of `4xy` indicates a transient negative reply. This means that for some reason, which is indicated by either the other digits or the comment, the command cannot be processed immediately, but there is some hope that the problem will only be transient. This is basically telling the client to try the same command again later. In contrast, a reply code of `5xy` indicates a permanent failure or error. In this case, it is useless for the client to retry the same command later. Other application layer protocols such as FTP :rfc:`959` or HTTP :rfc:`2616` use a similar structure for their reply codes. Additional details about the other reply codes may be found in :rfc:`5321`.
0/10570 · 1057
199
../../protocols/ipv6.rst:714
English
``2001:db8:1234:5678::AA`` is assigned to ``hostA``
0/510 · 51
200
../../glossary.rst:35
English
Wide Area Network
0/170 · 17
200
../../principles/linkstate.rst:129
English
It should be noted that link state routing assumes that all routers in the network have enough memory to store the entire LSDB. The routers that do not have enough memory to store the entire LSDB cannot participate in link state routing. Some link state routing protocols allow routers to report that they do not have enough memory and must be removed from the graph by the other routers in the network, but this is outside the scope of this e-book.
0/4490 · 449