cnp3-ebook - English @ Weblate

Exit Zen

217 ../../protocols/email.rst:482

	English Footnotes 9/10000 · 9
217 ../../protocols/ipv6.rst:796

	English Routers regularly send Router Advertisement messages. These messages are triggered by a timer that is often set at approximately 30 seconds. Usually, hosts wait for the arrival of a Router Advertisement message to configure their address. This implies that hosts could sometimes need to wait 30 seconds before being able to configure their address. If this delay is too long, a host can also send a `Router Solicitation` message. This message is sent towards the multicast address that corresponds to all IPv6 routers (i.e. ``FF01::2``) and the default router will reply. 571/10000 · 571
218 ../../protocols/email.rst:483

	English It could be surprising that the `To:` is not mandatory inside an email message. While most email messages will contain this header line an email that does not contain a `To:` header line and that relies on the `bcc:` to specify the recipient is valid as well. 259/10000 · 259
218 ../../protocols/ipv6.rst:798

	English The last point that needs to be explained about ICMPv6 is the `Redirect` message. This message is used when there is more than one router on a subnet as shown in the figure below. 179/10000 · 179
219 ../../protocols/email.rst:485

	English The list of all standard email header lines may be found at http://www.iana.org/assignments/message-headers/message-header-index.html 133/10000 · 133
219 ../../protocols/ipv6.rst:819

	English In this network, ``router1`` is the default router for all hosts. The second router, ``router2`` provides connectivity to a specific IPv6 subnet, e.g. ``2001:db8:abcd::/48``. These two routers attached to the same subnet can be used in different ways. First, it is possible to manually configure the routing tables on all hosts to add a route towards ``2001:db8:abcd::/48`` via ``router2``. Unfortunately, forcing such manual configuration boils down all the benefits of using address auto-configuration in IPv6. The second approach is to automatically configure a default route via ``router1`` on all hosts. With such route, when a host needs to send a packet to any address within ``2001:db8:abcd::/48``, it will send it to ``router1``. ``router1`` would consult its routing table and find that the packet needs to be sent again on the subnet to reach ``router2``. This is a waste of time. A better approach would be to enable the hosts to automatically learn the new route. This is possible thanks to the ICMPv6 `Redirect` message. When ``router1`` receives a packet that needs to be forwarded back on the same interface, it replies with a `Redirect` message that indicates that the packet should have been sent via ``router2``. Upon reception of a `Redirect` message, the host updates it forwarding table to include a new transient entry for the destination reported in the message. A timeout is usually associated with this transient entry to automatically delete it after some time. 1490/10000 · 1490
220 ../../protocols/email.rst:487

	English During the last years, many Internet Service Providers, campus and enterprise networks have deployed SMTP extensions :rfc:`4954` on their MSAs. These extensions force the MUAs to be authenticated before the MSA accepts an email message from the MUA. 249/10000 · 249
220 ../../protocols/ipv6.rst:826

	English An alternative is the Dynamic Host Configuration Protocol (DHCP) defined in :rfc:`2131` and :rfc:`3315`. DHCP allows a host to automatically retrieve its assigned IPv6 address, but relies on server. A DHCP server is associated to each subnet [#fdhcpserver]_. Each DHCP server manages a pool of IPv6 addresses assigned to the subnet. When a host is first attached to the subnet, it sends a DHCP request message in a UDP segment (the DHCP server listens on port 67). As the host knows neither its IPv6 address nor the IPv6 address of the DHCP server, this UDP segment is sent inside a multicast packet target at the DHCP servers. The DHCP request may contain various options such as the name of the host, its datalink layer address, etc. The server captures the DHCP request and selects an unassigned address in its address pool. It then sends the assigned IPv6 address in a DHCP reply message which contains the datalink layer address of the host and additional information such as the subnet mask, the address of the default router or the address of the DNS resolver. The DHCP reply also specifies the lifetime of the address allocation. This forces the host to renew its address allocation once it expires. Thanks to the limited lease time, IP addresses are automatically returned to the pool of addresses when hosts are powered off. 1336/10000 · 1336
221 ../../protocols/email.rst:489

	English The first versions of SMTP used `HELO` as the first command sent by a client to a SMTP server. When SMTP was extended to support newer features such as 8 bits characters, it was necessary to allow a server to recognize whether it was interacting with a client that supported the extensions or not. `EHLO` became mandatory with the publication of :rfc:`2821`. 358/10000 · 358
221 ../../protocols/ipv6.rst:828

	English Both SLAAC and DHCPv6 can be extended to provide additional information beyond the IPv6 prefix/address. For example, :rfc:`6106` defines options for the ICMPv6 ND message that can carry the IPv6 address of the recursive DNS resolver and a list of default domain search suffixes. It is also possible to combine SLAAC with DHCPv6. :rfc:`3736` defines a stateless variant of DHCPv6 that can be used to distribute DNS information while SLAAC is used to distribute the prefixes. 473/10000 · 473
222 ../../protocols/email.rst:491

	English This implies that a valid email message cannot contain a line with one dot followed by `CR` and `LF`. If a user types such a line in an email, his email client will automatically add a space character before or after the dot when sending the message over SMTP. 260/10000 · 260
222 ../../protocols/ipv6.rst:834

	English Footnotes 9/10000 · 9
223 ../../protocols/email.rst:493

	English :rfc:`1939` defines the APOP authentication scheme that is not vulnerable to such attacks. 90/10000 · 90
223 ../../protocols/ipv6.rst:835

	English The full list of allocated IPv6 multicast addresses is available at http://www.iana.org/assignments/ipv6-multicast-addresses 124/10000 · 124
224 ../../protocols/ipv6.rst:837

	English The IANA_ maintains the list of all allocated Next Header types at http://www.iana.org/assignments/protocol-numbers/ 116/10000 · 116
225 ../../protocols/ipv6.rst:839

	English When IPv4 was designed, the situation was different. The IPv4 header includes a checksum that only covers the network header. This checksum is computed by the source and updated by all intermediate routers that decrement the TTL, which is the IPv4 equivalent of the `HopLimit` used by IPv6. 290/10000 · 290
226 ../../protocols/ipv6.rst:841

	English Until a few years ago, all hosts replied to `Echo request` ICMP messages. However, due to the security problems that have affected TCP/IP implementations, many of these implementations can now be configured to disable answering `Echo request` ICMP messages. 257/10000 · 257
227 ../../protocols/ipv6.rst:843

	English For a discussion of the issues with the router alert IP option, see http://tools.ietf.org/html/draft-rahman-rtg-router-alert-dangerous-00 or http://tools.ietf.org/html/draft-rahman-rtg-router-alert-considerations-03 215/10000 · 215
228 ../../protocols/ipv6.rst:846

	English For simplicity, you assume that each datalink layer interface is assigned a 64 bits MAC address. As we will see later, today's datalink layer technologies mainly use 48 bits MAC addresses, but the smaller addresses can easily be converted into 64 bits addresses. 262/10000 · 262
229 ../../protocols/ipv6.rst:848

	English :rfc:`4291` and :rfc:`4861` explain in more details how the IPv6 multicast address is determined from the target IPv6 unicast address. These details are outside the scope of this book, but may matter if you try to understand a packet trace. 240/10000 · 240

Shortcut	Action
`?`	Open available keyboard shortcuts.
`Alt` + `Home`	Navigate to the first translation in the current search.
`Alt` + `End`	Navigate to the last translation in the current search.
`Alt` + `PageUp` or `Ctrl` + `↑` or `Alt` + `↑` or `Cmd` + `↑` or	Navigate to the previous translation in the current search.
`Alt` + `PageDown` or `Ctrl` + `↓` or `Alt` + `↓` or `Cmd` + `↓` or	Navigate to the next translation in the current search.
`Ctrl` + `Enter` or `Cmd` + `Enter`	Submit current form; this works the same as pressing Save and continue while editing translation.
`Ctrl` + `Shift` + `Enter` or `Cmd` + `Shift` +`Enter`	Unmark translation as Needing edit and submit it.
`Alt` + `Enter` or `Option` + `Enter`	Submit the string as a suggestion; this works the same as pressing Suggest while editing translation.
`Ctrl` + `E` or `Cmd` + `E`	Focus on translation editor.
`Ctrl` + `U` or `Cmd` + `U`	Focus on comment editor.
`Ctrl` + `M` or `Cmd` + `M`	Shows Automatic suggestions tab.
`Ctrl` + `1` to `Ctrl` + `9` or `Cmd` + `1` to `Cmd` + `9`	Copies placeable of a given number from source string.
`Ctrl` + `M` followed by `1` to `9` or `Cmd` + `M` followed by `1` to `9`	Copy the machine translation of a given number to current translation.
`Ctrl` + `I` followed by `1` to `9` or `Cmd` + `I` followed by `1` to `9`	Ignore one item in the list of failing checks.
`Ctrl` + `J` or `Cmd` + `J`	Shows the Nearby strings tab.
`Ctrl` + `S` or `Cmd` + `S`	Focus on search field.
`Ctrl` + `O` or `Cmd` + `O`	Copy the source string.
`Ctrl` + `Y` or `Cmd` + `Y`	Toggle the Needs editing checkbox.
`→`	Browse the next translation string.
`←`	Browse the previous translation string.