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192 ../../protocols/email.rst:344
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The Simple Mail Transfer Protocol (:term:`SMTP`) defined in :rfc:`5321` is a client-server protocol. The SMTP specification distinguishes between five types of processes involved in the delivery of email messages. Email messages are composed on a Mail User Agent (MUA). The MUA is usually either an email client or a webmail. The MUA sends the email message to a Mail Submission Agent (MSA). The MSA processes the received email and forwards it to the Mail Transmission Agent (MTA). The MTA is responsible for the transmission of the email, directly or via intermediate MTAs to the MTA of the destination domain. This destination MTA will then forward the message to the Mail Delivery Agent (MDA) where it will be accessed by the recipient's MUA. SMTP is used for the interactions between MUA and MSA [#fsmtpauth]_, MSA-MTA and MTA-MTA. 836/10000 · 836
192 ../../protocols/ipv6.rst:680
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A MAC address 13/10000 · 13
192 ../../protocols/tcp.rst:642
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A complete TCP implementation contains additional information in its TCB, notably to support the `urgent` pointer. However, this part of TCP is not discussed in this book. Refer to :rfc:`793` and :rfc:`2140` for more details about the TCB. 239/10000 · 239
193 ../../glossary.rst:45
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — W3C 3/10000 · 3
193 ../../principles/reliability.rst:986
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 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. 440/10000 · 440
193 ../../protocols/email.rst:346
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — SMTP is a text-based protocol like many other application-layer protocols on the Internet. It relies on the byte-stream service. Servers listen on port `25`. Clients send commands that are each composed of one line of ASCII text terminated by `CR+LF`. Servers reply by sending ASCII lines that contain a three digit numerical error/success code and optional comments. 367/10000 · 367
193 ../../protocols/ipv6.rst:682
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — MAC addresses are allocated in blocks of :math:`2^{20}`. When a company registers for a block of MAC addresses, it receives an identifier. company identifier is then used to populated the `c` bits of the MAC addresses. The company can allocate all addresses in starting with this prefix and manages the `m` bits as it wishes. 325/10000 · 325
193 ../../protocols/tcp.rst:646
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — This TCP segment is then placed in an IP header. We describe IPv6 in the next chapter. The minimum size of the IPv6 (resp. IPv4) header is 40 bytes (resp. 20 bytes). 165/10000 · 165
193 ../../principles/linkstate.rst:334
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — When a link is reported in the LSP of only one of the attached routers, routers consider the link as having failed and they remove it from the directed graph that they compute from their LSDB. This is called the `two-way connectivity check`. This check allows link failures to be quickly flooded as a single LSP is sufficient to announce such bad news. However, when a link comes up, it can only be used once the two attached routers have sent their LSPs. The `two-way connectivity check` also allows for dealing with router failures. When a router fails, all its links fail by definition. These failures are reported in the LSPs sent by the neighbors of the failed router. The failed router does not, of course, send a new LSP to announce its failure. However, in the graph that represents the network, this failed router appears as a node that only has outgoing edges. Thanks to the `two-way connectivity check`, this failed router cannot be considered as a transit router to reach any destination since no outgoing edge is attached to it. 1041/10000 · 1041
194 ../../glossary.rst:47
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 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 193/10000 · 193
194 ../../principles/reliability.rst:990
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Maximum window size with `go-back-n` and `selective repeat` 59/10000 · 59
194 ../../principles/linkstate.rst:336
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 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. 573/10000 · 573
194 ../../protocols/email.rst:348
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The SMTP protocol, like most text-based protocols, is specified as a :term:`BNF`. The full BNF is defined in :rfc:`5321`. The main SMTP commands are defined by the BNF rules shown in the figure below. 200/10000 · 200
194 ../../protocols/ipv6.rst:687
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A MAC address converted into a 64 bits host identifier 54/10000 · 54
194 ../../protocols/tcp.rst:649
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A precise estimation of the maximum bandwidth that can be achieved by a TCP connection should take into account the overhead of the TCP and IP headers as well. 159/10000 · 159
195 ../../glossary.rst:33
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — WAN 3/10000 · 3
195 ../../principles/reliability.rst:992
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 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. 1035/10000 · 1035
195 ../../principles/linkstate.rst:338
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — 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. 247/10000 · 247
195 ../../protocols/email.rst:354
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — BNF specification of the SMTP commands 38/10000 · 38
195 ../../protocols/ipv6.rst:689
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Inside a MAC address, the two bits indicated as `0` and `g` in the figure above play a special role. The first bit indicates whether the address is universal or local. The `g` bit indicates whether this is a multicast address or a unicast address. The MAC address can be converted into a 64 bits host identifier by flipping the value of the `0` bit and inserting ``FFFE``, i.e. ``1111111111111110`` in binary, in the middle of the address as shown in the figure below. The `c`, `m` and `g` bits of the MAC address are not modified. 531/10000 · 531