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../../protocols/ethernet.rst:415
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IEEE defined in the [IEEE802.1q]_ standard a special header to encode the VLAN identifiers. This 32 bit header includes a 12 bit VLAN field that contains the VLAN identifier of each frame. The format of the [IEEE802.1q]_ header is described below.
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../../protocols/tcp.rst:372
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Evolution of the round-trip-time between two hosts
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../../glossary.rst:220
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NTP
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../../principles/dv.rst:59
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The first condition ensures that the router discovers the shortest path towards each destination. The second condition is used to take into account the changes of routes that may occur after a link failure or a change of the metric associated to a link.
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../../principles/transport.rst:699
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Three-way handshake : recovery from a duplicate `CA`
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../../principles/sharing.rst:624
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A Token Ring network is composed of a set of stations that are attached to a unidirectional ring. The basic principle of the Token Ring MAC algorithm is that two types of frames travel on the ring : tokens and data frames. When the Token Ring starts, one of the stations sends the token. The token is a small frame that represents the authorization to transmit data frames on the ring. To transmit a data frame on the ring, a station must first capture the token by removing it from the ring. As only one station can capture the token at a time, the station that owns the token can safely transmit a data frame on the ring without risking collisions. After having transmitted its frame, the station must remove it from the ring and resend the token so that other stations can transmit their own frames.
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../../protocols/bgp.rst:465
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Due to this organization of the Internet and due to the BGP decision process, most AS-level paths on the Internet have a length of 3-5 AS hops.
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../../protocols/email.rst:254
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../../protocols/ipv6.rst:412
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Although IPv6 can send 64 KBytes long packets, few datalink layer technologies that are used today are able to send a 64 KBytes packet inside a frame. Furthermore, as illustrated in the figure below, another problem is that a host may send a packet that would be too large for one of the datalink layers used by the intermediate routers.
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../../protocols/ethernet.rst:421
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Format of the 802.1q header
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../../protocols/tcp.rst:375
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The easiest solution to measure the round-trip-time on a TCP connection is to measure the delay between the transmission of a data segment and the reception of a corresponding acknowledgment [#frttmes]_. As illustrated in the figure below, this measurement works well when there are no segment losses.
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../../glossary.rst:222
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The Network Time Protocol is defined in :rfc:`1305`
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../../principles/dv.rst:61
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To understand the operation of a distance vector protocol, let us consider the network of five routers shown below.
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../../principles/reliability.rst:431 • ../../principles/reliability.rst:432 • ../../principles/reliability.rst:433 • ../../principles/reliability.rst:434 • ../../principles/reliability.rst:435 • ../../principles/reliability.rst:436 • ../../principles/reliability.rst:437 • ../../principles/reliability.rst:438 • ../../principles/reliability.rst:448 • ../../principles/reliability.rst:449 • ../../principles/reliability.rst:450 • ../../principles/reliability.rst:451
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../../principles/sharing.rst:632
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A Token Ring network
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../../protocols/bgp.rst:470
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Footnotes
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../../protocols/email.rst:254
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../../protocols/ipv6.rst:418
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The need for fragmentation and reassembly
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../../protocols/ethernet.rst:423
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The [IEEE802.1q]_ header is inserted immediately after the source MAC address in the Ethernet frame (i.e. before the EtherType field). The maximum frame size is increased by 4 bytes. It is encoded in 32 bits and contains four fields. The Tag Protocol Identifier is set to `0x8100` to allow the receiver to detect the presence of this additional header. The `Priority Code Point` (PCP) is a three bit field that is used to support different transmission priorities for the frame. Value `0` is the lowest priority and value `7` the highest. Frames with a higher priority can expect to be forwarded earlier than frames having a lower priority. The `C` bit is used for compatibility between Ethernet and Token Ring networks. The last 12 bits of the 802.1q header contain the VLAN identifier. Value `0` indicates that the frame does not belong to any VLAN while value `0xFFF` is reserved. This implies that 4094 different VLAN identifiers can be used in an Ethernet network.
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