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The :math:`2*MSL` seconds delay in the `TIME\_WAIT` state is an important operational problem on servers having thousands of simultaneously opened TCP connections [FTY99]_. Consider for example a busy web server that processes 10.000 TCP connections every second. If each of these connections remains in the `TIME\_WAIT` state for 4 minutes, this implies that the server would have to maintain more than 2 million TCBs at any time. For this reason, some TCP implementations prefer to perform an abrupt connection release by sending a `RST` segment to close the connection [AW05]_ and immediately discard the corresponding :term:`TCB`. However, if the `RST` segment is lost, the remote host continues to maintain a :term:`TCB` for a connection that no longer exists. This optimization reduces the number of TCBs maintained by the host sending the `RST` segment but at the potential cost of increased processing on the remote host when the `RST` segment is lost.
The :math:`2*MSL` seconds delay in the `TIME\_WAIT` state is an important operational problem on servers having thousands of simultaneously opened TCP connections [FTY99]_. Consider for example a busy web server that processes 10.000 TCP connections every second. If each of these connections remains in the `TIME\_WAIT` state for 4 minutes, this implies that the server would have to maintain more than 2 million TCBs at any time. For this reason, some TCP implementations prefer to perform an abrupt connection release by sending a `RST` segment to close the connection [AW05]_ and immediately discard the corresponding :term:`TCB`. However, if the `RST` segment is lost, the remote host continues to maintain a :term:`TCB` for a connection that no longer exists. This optimization reduces the number of TCBs maintained by the host sending the `RST` segment but at the potential cost of increased processing on the remote host when the `RST` segment is lost.
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The second path is when the host has transmitted all data. Assume that the last transmitted sequence number is `z`. Then, the host sends a `FIN` segment with sequence number :math:`(z+1) \pmod{2^{32}}` and enters the `FIN_WAIT1` state. In this state, it can retransmit unacknowledged segments but cannot send new data segments. It waits for an acknowledgment of its `FIN` segment (i.e. sequence number :math:`(z+1) \pmod{2^{32}}`), but may receive a `FIN` segment sent by the remote host. In the first case, the TCP connection enters the `FIN\_WAIT2` state. In this state, new data segments from the remote host are still accepted until the reception of the `FIN` segment. The acknowledgment for this `FIN` segment is sent once all data received before the `FIN` segment have been delivered to the user and the connection enters the `TIME\_WAIT` state. In the second case, a `FIN` segment is received and the connection enters the `Closing` state once all data received from the remote host have been delivered to the user. In this state, no new data segments can be sent and the host waits for an acknowledgment of its `FIN` segment before entering the `TIME\_WAIT` state.
The second path is when the host has transmitted all data. Assume that the last transmitted sequence number is `z`. Then, the host sends a `FIN` segment with sequence number :math:`(z+1) \pmod{2^{32}}` and enters the `FIN_WAIT1` state. In this state, it can retransmit unacknowledged segments but cannot send new data segments. It waits for an acknowledgment of its `FIN` segment (i.e. sequence number :math:`(z+1) \pmod{2^{32}}`), but may receive a `FIN` segment sent by the remote host. In the first case, the TCP connection enters the `FIN\_WAIT2` state. In this state, new data segments from the remote host are still accepted until the reception of the `FIN` segment. The acknowledgment for this `FIN` segment is sent once all data received before the `FIN` segment have been delivered to the user and the connection enters the `TIME\_WAIT` state. In the second case, a `FIN` segment is received and the connection enters the `Closing` state once all data received from the remote host have been delivered to the user. In this state, no new data segments can be sent and the host waits for an acknowledgment of its `FIN` segment before entering the `TIME\_WAIT` state.
3 years ago
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File “locale/pot/protocols/ssh.pot” was added. 3 years ago
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File “locale/pot/protocols/rpc.pot” was added. 3 years ago
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File “locale/pot/protocols/routing.pot” was added. 3 years ago
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File “locale/pot/protocols/ppp.pot” was added. 3 years ago
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File “locale/pot/protocols/lan.pot” was added. 3 years ago
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We will use the notation `<R,c,T,p>` to represent a `BPDU` whose `root identifier` is `R`, `cost` is `c` and that was sent from the port `p` of switch `T`. The construction of the spanning tree depends on an ordering relationship among the `BPDUs`. This ordering relationship could be implemented by the Python function below.
We will use the notation `<R,c,T,p>` to represent a `BPDU` whose `root identifier` is `R`, `cost` is `c` and that was sent from the port `p` of switch `T`. The construction of the spanning tree depends on an ordering relationship among the `BPDUs`. This ordering relationship could be implemented by the Python function below.
3 years ago
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File “locale/pot/protocols/ipv6.pot” was added. 3 years ago
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File “locale/pot/protocols/http2.pot” was added. 3 years ago
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HTTP/2.0 is a new version of the HTTP protocol that still uses port 80. When a client contacts an HTTP server, it must be able to determine whether it supports HTTP/1.x or HTTP/2.0. If the client sends a binary encoded HTTP/2.0 request to a server that only supports the ASCII encoded HTTP/1.x, it could cause problems on the server and even crash it. To minimize the risk of crashing HTTP/1.x servers, an HTTP/2.0 session starts like an HTTP/1.1 session and the first request contains the `Connection`, `Upgrade` and `HTTP2-Settings` headers. An example of such a request to upgrade the version of HTTP is shown below.
HTTP/2.0 is a new version of the HTTP protocol that still uses port 80. When a client contacts an HTTP server, it must be able to determine whether it supports HTTP/1.x or HTTP/2.0. If the client sends a binary encoded HTTP/2.0 request to a server that only supports the ASCII encoded HTTP/1.x, it could cause problems on the server and even crash it. To minimize the risk of crashing HTTP/1.x servers, an HTTP/2.0 session starts like an HTTP/1.1 session and the first request contains the `Connection`, `Upgrade` and `HTTP2-Settings` headers. An example of such a request to upgrade the version of HTTP is shown below.
3 years ago
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One of the limitations of HTTP from a performance viewpoint is that the requests that are sent by a browser must be sequential. Typically, a browser requests the HTML page. Once the page has been retrieved, the browser parses it to identify all the objects that it references and requests them one after each other. The web page can only be displayed to the user once all the required web objects have been retrieved. This implies that the browser must wait until the reception of each response before sending the next request. Another possibility is to allow the browser to send multiple requests without waiting for their corresponding responses. This approach is called `pipelining` in :rfc:`7230`.
One of the limitations of HTTP from a performance viewpoint is that the requests that are sent by a browser must be sequential. Typically, a browser requests the HTML page. Once the page has been retrieved, the browser parses it to identify all the objects that it references and requests them one after each other. The web page can only be displayed to the user once all the required web objects have been retrieved. This implies that the browser must wait until the reception of each response before sending the next request. Another possibility is to allow the browser to send multiple requests without waiting for their corresponding responses. This approach is called `pipelining` in :rfc:`7230`.
3 years ago
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Two directions have been explored to improve the delivery of these web pages. The first direction is to tune the HTTP protocol. The second approach is to change the entire network stack. We will discuss this approach after having covered the entire stack.
Two directions have been explored to improve the delivery of these web pages. The first direction is to tune the HTTP protocol. The second approach is to change the entire network stack. We will discuss this approach after having covered the entire stack.
3 years ago
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File “locale/pot/protocols/http.pot” was added. 3 years ago
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In the early days, the Internet was mainly used for remote terminal access with telnet_, email and file transfer. The default file transfer protocol, `FTP`, defined in :rfc:`959` was widely used. `FTP` clients and servers are still included in some operating systems.
In the early days, the Internet was mainly used for remote terminal access with telnet_, email and file transfer. The default file transfer protocol, `FTP`, defined in :rfc:`959` was widely used. `FTP` clients and servers are still included in some operating systems.
3 years ago
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File “locale/pot/protocols/ethernet.pot” was added. 3 years ago
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We will use the notation `<R,c,T,p>` to represent a `BPDU` whose `root identifier` is `R`, `cost` is `c` and that was sent from the port `p` of switch `T`. The construction of the spanning tree depends on an ordering relationship among the `BPDUs`. This ordering relationship could be implemented by the Python function below.
We will use the notation `<R,c,T,p>` to represent a `BPDU` whose `root identifier` is `R`, `cost` is `c` and that was sent from the port `p` of switch `T`. The construction of the spanning tree depends on an ordering relationship among the `BPDUs`. This ordering relationship could be implemented by the Python function below.
3 years ago
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File “locale/pot/protocols/email.pot” was added. 3 years ago
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File “locale/pot/protocols/dnssec.pot” was added. 3 years ago
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File “locale/pot/protocols/congestion.pot” was added. 3 years ago

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