diff options
Diffstat (limited to 'Documentation/networking')
-rw-r--r-- | Documentation/networking/00-INDEX | 2 | ||||
-rw-r--r-- | Documentation/networking/cxacru-cf.py | 48 | ||||
-rw-r--r-- | Documentation/networking/cxacru.txt | 16 | ||||
-rw-r--r-- | Documentation/networking/dccp.txt | 6 | ||||
-rw-r--r-- | Documentation/networking/ip-sysctl.txt | 66 | ||||
-rwxr-xr-x | Documentation/networking/ixgbevf.txt | 90 | ||||
-rw-r--r-- | Documentation/networking/packet_mmap.txt | 8 | ||||
-rw-r--r-- | Documentation/networking/regulatory.txt | 24 | ||||
-rw-r--r-- | Documentation/networking/tcp-thin.txt | 47 |
9 files changed, 294 insertions, 13 deletions
diff --git a/Documentation/networking/00-INDEX b/Documentation/networking/00-INDEX index 50189bf07d53..fe5c099b8fc8 100644 --- a/Documentation/networking/00-INDEX +++ b/Documentation/networking/00-INDEX | |||
@@ -32,6 +32,8 @@ cs89x0.txt | |||
32 | - the Crystal LAN (CS8900/20-based) Ethernet ISA adapter driver | 32 | - the Crystal LAN (CS8900/20-based) Ethernet ISA adapter driver |
33 | cxacru.txt | 33 | cxacru.txt |
34 | - Conexant AccessRunner USB ADSL Modem | 34 | - Conexant AccessRunner USB ADSL Modem |
35 | cxacru-cf.py | ||
36 | - Conexant AccessRunner USB ADSL Modem configuration file parser | ||
35 | de4x5.txt | 37 | de4x5.txt |
36 | - the Digital EtherWORKS DE4?? and DE5?? PCI Ethernet driver | 38 | - the Digital EtherWORKS DE4?? and DE5?? PCI Ethernet driver |
37 | decnet.txt | 39 | decnet.txt |
diff --git a/Documentation/networking/cxacru-cf.py b/Documentation/networking/cxacru-cf.py new file mode 100644 index 000000000000..b41d298398c8 --- /dev/null +++ b/Documentation/networking/cxacru-cf.py | |||
@@ -0,0 +1,48 @@ | |||
1 | #!/usr/bin/env python | ||
2 | # Copyright 2009 Simon Arlott | ||
3 | # | ||
4 | # This program is free software; you can redistribute it and/or modify it | ||
5 | # under the terms of the GNU General Public License as published by the Free | ||
6 | # Software Foundation; either version 2 of the License, or (at your option) | ||
7 | # any later version. | ||
8 | # | ||
9 | # This program is distributed in the hope that it will be useful, but WITHOUT | ||
10 | # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
11 | # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for | ||
12 | # more details. | ||
13 | # | ||
14 | # You should have received a copy of the GNU General Public License along with | ||
15 | # this program; if not, write to the Free Software Foundation, Inc., 59 | ||
16 | # Temple Place - Suite 330, Boston, MA 02111-1307, USA. | ||
17 | # | ||
18 | # Usage: cxacru-cf.py < cxacru-cf.bin | ||
19 | # Output: values string suitable for the sysfs adsl_config attribute | ||
20 | # | ||
21 | # Warning: cxacru-cf.bin with MD5 hash cdbac2689969d5ed5d4850f117702110 | ||
22 | # contains mis-aligned values which will stop the modem from being able | ||
23 | # to make a connection. If the first and last two bytes are removed then | ||
24 | # the values become valid, but the modulation will be forced to ANSI | ||
25 | # T1.413 only which may not be appropriate. | ||
26 | # | ||
27 | # The original binary format is a packed list of le32 values. | ||
28 | |||
29 | import sys | ||
30 | import struct | ||
31 | |||
32 | i = 0 | ||
33 | while True: | ||
34 | buf = sys.stdin.read(4) | ||
35 | |||
36 | if len(buf) == 0: | ||
37 | break | ||
38 | elif len(buf) != 4: | ||
39 | sys.stdout.write("\n") | ||
40 | sys.stderr.write("Error: read {0} not 4 bytes\n".format(len(buf))) | ||
41 | sys.exit(1) | ||
42 | |||
43 | if i > 0: | ||
44 | sys.stdout.write(" ") | ||
45 | sys.stdout.write("{0:x}={1}".format(i, struct.unpack("<I", buf)[0])) | ||
46 | i += 1 | ||
47 | |||
48 | sys.stdout.write("\n") | ||
diff --git a/Documentation/networking/cxacru.txt b/Documentation/networking/cxacru.txt index b074681a963e..2cce04457b4d 100644 --- a/Documentation/networking/cxacru.txt +++ b/Documentation/networking/cxacru.txt | |||
@@ -4,6 +4,12 @@ While it is capable of managing/maintaining the ADSL connection without the | |||
4 | module loaded, the device will sometimes stop responding after unloading the | 4 | module loaded, the device will sometimes stop responding after unloading the |
5 | driver and it is necessary to unplug/remove power to the device to fix this. | 5 | driver and it is necessary to unplug/remove power to the device to fix this. |
6 | 6 | ||
7 | Note: support for cxacru-cf.bin has been removed. It was not loaded correctly | ||
8 | so it had no effect on the device configuration. Fixing it could have stopped | ||
9 | existing devices working when an invalid configuration is supplied. | ||
10 | |||
11 | There is a script cxacru-cf.py to convert an existing file to the sysfs form. | ||
12 | |||
7 | Detected devices will appear as ATM devices named "cxacru". In /sys/class/atm/ | 13 | Detected devices will appear as ATM devices named "cxacru". In /sys/class/atm/ |
8 | these are directories named cxacruN where N is the device number. A symlink | 14 | these are directories named cxacruN where N is the device number. A symlink |
9 | named device points to the USB interface device's directory which contains | 15 | named device points to the USB interface device's directory which contains |
@@ -15,6 +21,15 @@ several sysfs attribute files for retrieving device statistics: | |||
15 | * adsl_headend_environment | 21 | * adsl_headend_environment |
16 | Information about the remote headend. | 22 | Information about the remote headend. |
17 | 23 | ||
24 | * adsl_config | ||
25 | Configuration writing interface. | ||
26 | Write parameters in hexadecimal format <index>=<value>, | ||
27 | separated by whitespace, e.g.: | ||
28 | "1=0 a=5" | ||
29 | Up to 7 parameters at a time will be sent and the modem will restart | ||
30 | the ADSL connection when any value is set. These are logged for future | ||
31 | reference. | ||
32 | |||
18 | * downstream_attenuation (dB) | 33 | * downstream_attenuation (dB) |
19 | * downstream_bits_per_frame | 34 | * downstream_bits_per_frame |
20 | * downstream_rate (kbps) | 35 | * downstream_rate (kbps) |
@@ -61,6 +76,7 @@ several sysfs attribute files for retrieving device statistics: | |||
61 | * mac_address | 76 | * mac_address |
62 | 77 | ||
63 | * modulation | 78 | * modulation |
79 | "" (when not connected) | ||
64 | "ANSI T1.413" | 80 | "ANSI T1.413" |
65 | "ITU-T G.992.1 (G.DMT)" | 81 | "ITU-T G.992.1 (G.DMT)" |
66 | "ITU-T G.992.2 (G.LITE)" | 82 | "ITU-T G.992.2 (G.LITE)" |
diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index b132e4a3cf0f..a62fdf7a6bff 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt | |||
@@ -58,8 +58,10 @@ DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet | |||
58 | size (application payload size) in bytes, see RFC 4340, section 14. | 58 | size (application payload size) in bytes, see RFC 4340, section 14. |
59 | 59 | ||
60 | DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs | 60 | DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs |
61 | supported by the endpoint (see include/linux/dccp.h for symbolic constants). | 61 | supported by the endpoint. The option value is an array of type uint8_t whose |
62 | The caller needs to provide a sufficiently large (> 2) array of type uint8_t. | 62 | size is passed as option length. The minimum array size is 4 elements, the |
63 | value returned in the optlen argument always reflects the true number of | ||
64 | built-in CCIDs. | ||
63 | 65 | ||
64 | DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same | 66 | DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same |
65 | time, combining the operation of the next two socket options. This option is | 67 | time, combining the operation of the next two socket options. This option is |
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 006b39dec87d..8b72c88ba213 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt | |||
@@ -487,6 +487,30 @@ tcp_dma_copybreak - INTEGER | |||
487 | and CONFIG_NET_DMA is enabled. | 487 | and CONFIG_NET_DMA is enabled. |
488 | Default: 4096 | 488 | Default: 4096 |
489 | 489 | ||
490 | tcp_thin_linear_timeouts - BOOLEAN | ||
491 | Enable dynamic triggering of linear timeouts for thin streams. | ||
492 | If set, a check is performed upon retransmission by timeout to | ||
493 | determine if the stream is thin (less than 4 packets in flight). | ||
494 | As long as the stream is found to be thin, up to 6 linear | ||
495 | timeouts may be performed before exponential backoff mode is | ||
496 | initiated. This improves retransmission latency for | ||
497 | non-aggressive thin streams, often found to be time-dependent. | ||
498 | For more information on thin streams, see | ||
499 | Documentation/networking/tcp-thin.txt | ||
500 | Default: 0 | ||
501 | |||
502 | tcp_thin_dupack - BOOLEAN | ||
503 | Enable dynamic triggering of retransmissions after one dupACK | ||
504 | for thin streams. If set, a check is performed upon reception | ||
505 | of a dupACK to determine if the stream is thin (less than 4 | ||
506 | packets in flight). As long as the stream is found to be thin, | ||
507 | data is retransmitted on the first received dupACK. This | ||
508 | improves retransmission latency for non-aggressive thin | ||
509 | streams, often found to be time-dependent. | ||
510 | For more information on thin streams, see | ||
511 | Documentation/networking/tcp-thin.txt | ||
512 | Default: 0 | ||
513 | |||
490 | UDP variables: | 514 | UDP variables: |
491 | 515 | ||
492 | udp_mem - vector of 3 INTEGERs: min, pressure, max | 516 | udp_mem - vector of 3 INTEGERs: min, pressure, max |
@@ -692,6 +716,25 @@ proxy_arp - BOOLEAN | |||
692 | conf/{all,interface}/proxy_arp is set to TRUE, | 716 | conf/{all,interface}/proxy_arp is set to TRUE, |
693 | it will be disabled otherwise | 717 | it will be disabled otherwise |
694 | 718 | ||
719 | proxy_arp_pvlan - BOOLEAN | ||
720 | Private VLAN proxy arp. | ||
721 | Basically allow proxy arp replies back to the same interface | ||
722 | (from which the ARP request/solicitation was received). | ||
723 | |||
724 | This is done to support (ethernet) switch features, like RFC | ||
725 | 3069, where the individual ports are NOT allowed to | ||
726 | communicate with each other, but they are allowed to talk to | ||
727 | the upstream router. As described in RFC 3069, it is possible | ||
728 | to allow these hosts to communicate through the upstream | ||
729 | router by proxy_arp'ing. Don't need to be used together with | ||
730 | proxy_arp. | ||
731 | |||
732 | This technology is known by different names: | ||
733 | In RFC 3069 it is called VLAN Aggregation. | ||
734 | Cisco and Allied Telesyn call it Private VLAN. | ||
735 | Hewlett-Packard call it Source-Port filtering or port-isolation. | ||
736 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | ||
737 | |||
695 | shared_media - BOOLEAN | 738 | shared_media - BOOLEAN |
696 | Send(router) or accept(host) RFC1620 shared media redirects. | 739 | Send(router) or accept(host) RFC1620 shared media redirects. |
697 | Overrides ip_secure_redirects. | 740 | Overrides ip_secure_redirects. |
@@ -833,9 +876,18 @@ arp_notify - BOOLEAN | |||
833 | or hardware address changes. | 876 | or hardware address changes. |
834 | 877 | ||
835 | arp_accept - BOOLEAN | 878 | arp_accept - BOOLEAN |
836 | Define behavior when gratuitous arp replies are received: | 879 | Define behavior for gratuitous ARP frames who's IP is not |
837 | 0 - drop gratuitous arp frames | 880 | already present in the ARP table: |
838 | 1 - accept gratuitous arp frames | 881 | 0 - don't create new entries in the ARP table |
882 | 1 - create new entries in the ARP table | ||
883 | |||
884 | Both replies and requests type gratuitous arp will trigger the | ||
885 | ARP table to be updated, if this setting is on. | ||
886 | |||
887 | If the ARP table already contains the IP address of the | ||
888 | gratuitous arp frame, the arp table will be updated regardless | ||
889 | if this setting is on or off. | ||
890 | |||
839 | 891 | ||
840 | app_solicit - INTEGER | 892 | app_solicit - INTEGER |
841 | The maximum number of probes to send to the user space ARP daemon | 893 | The maximum number of probes to send to the user space ARP daemon |
@@ -1074,10 +1126,10 @@ regen_max_retry - INTEGER | |||
1074 | Default: 5 | 1126 | Default: 5 |
1075 | 1127 | ||
1076 | max_addresses - INTEGER | 1128 | max_addresses - INTEGER |
1077 | Number of maximum addresses per interface. 0 disables limitation. | 1129 | Maximum number of autoconfigured addresses per interface. Setting |
1078 | It is recommended not set too large value (or 0) because it would | 1130 | to zero disables the limitation. It is not recommended to set this |
1079 | be too easy way to crash kernel to allow to create too much of | 1131 | value too large (or to zero) because it would be an easy way to |
1080 | autoconfigured addresses. | 1132 | crash the kernel by allowing too many addresses to be created. |
1081 | Default: 16 | 1133 | Default: 16 |
1082 | 1134 | ||
1083 | disable_ipv6 - BOOLEAN | 1135 | disable_ipv6 - BOOLEAN |
diff --git a/Documentation/networking/ixgbevf.txt b/Documentation/networking/ixgbevf.txt new file mode 100755 index 000000000000..19015de6725f --- /dev/null +++ b/Documentation/networking/ixgbevf.txt | |||
@@ -0,0 +1,90 @@ | |||
1 | Linux* Base Driver for Intel(R) Network Connection | ||
2 | ================================================== | ||
3 | |||
4 | November 24, 2009 | ||
5 | |||
6 | Contents | ||
7 | ======== | ||
8 | |||
9 | - In This Release | ||
10 | - Identifying Your Adapter | ||
11 | - Known Issues/Troubleshooting | ||
12 | - Support | ||
13 | |||
14 | In This Release | ||
15 | =============== | ||
16 | |||
17 | This file describes the ixgbevf Linux* Base Driver for Intel Network | ||
18 | Connection. | ||
19 | |||
20 | The ixgbevf driver supports 82599-based virtual function devices that can only | ||
21 | be activated on kernels with CONFIG_PCI_IOV enabled. | ||
22 | |||
23 | The ixgbevf driver supports virtual functions generated by the ixgbe driver | ||
24 | with a max_vfs value of 1 or greater. | ||
25 | |||
26 | The guest OS loading the ixgbevf driver must support MSI-X interrupts. | ||
27 | |||
28 | VLANs: There is a limit of a total of 32 shared VLANs to 1 or more VFs. | ||
29 | |||
30 | Identifying Your Adapter | ||
31 | ======================== | ||
32 | |||
33 | For more information on how to identify your adapter, go to the Adapter & | ||
34 | Driver ID Guide at: | ||
35 | |||
36 | http://support.intel.com/support/network/sb/CS-008441.htm | ||
37 | |||
38 | Known Issues/Troubleshooting | ||
39 | ============================ | ||
40 | |||
41 | Unloading Physical Function (PF) Driver Causes System Reboots When VM is | ||
42 | Running and VF is Loaded on the VM | ||
43 | ------------------------------------------------------------------------ | ||
44 | Do not unload the PF driver (ixgbe) while VFs are assigned to guests. | ||
45 | |||
46 | Support | ||
47 | ======= | ||
48 | |||
49 | For general information, go to the Intel support website at: | ||
50 | |||
51 | http://support.intel.com | ||
52 | |||
53 | or the Intel Wired Networking project hosted by Sourceforge at: | ||
54 | |||
55 | http://sourceforge.net/projects/e1000 | ||
56 | |||
57 | If an issue is identified with the released source code on the supported | ||
58 | kernel with a supported adapter, email the specific information related | ||
59 | to the issue to e1000-devel@lists.sf.net | ||
60 | |||
61 | License | ||
62 | ======= | ||
63 | |||
64 | Intel 10 Gigabit Linux driver. | ||
65 | Copyright(c) 1999 - 2009 Intel Corporation. | ||
66 | |||
67 | This program is free software; you can redistribute it and/or modify it | ||
68 | under the terms and conditions of the GNU General Public License, | ||
69 | version 2, as published by the Free Software Foundation. | ||
70 | |||
71 | This program is distributed in the hope it will be useful, but WITHOUT | ||
72 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
73 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for | ||
74 | more details. | ||
75 | |||
76 | You should have received a copy of the GNU General Public License along with | ||
77 | this program; if not, write to the Free Software Foundation, Inc., | ||
78 | 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. | ||
79 | |||
80 | The full GNU General Public License is included in this distribution in | ||
81 | the file called "COPYING". | ||
82 | |||
83 | Trademarks | ||
84 | ========== | ||
85 | |||
86 | Intel, Itanium, and Pentium are trademarks or registered trademarks of | ||
87 | Intel Corporation or its subsidiaries in the United States and other | ||
88 | countries. | ||
89 | |||
90 | * Other names and brands may be claimed as the property of others. | ||
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index a22fd85e3796..09ab0d290326 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt | |||
@@ -2,7 +2,7 @@ | |||
2 | + ABSTRACT | 2 | + ABSTRACT |
3 | -------------------------------------------------------------------------------- | 3 | -------------------------------------------------------------------------------- |
4 | 4 | ||
5 | This file documents the CONFIG_PACKET_MMAP option available with the PACKET | 5 | This file documents the mmap() facility available with the PACKET |
6 | socket interface on 2.4 and 2.6 kernels. This type of sockets is used for | 6 | socket interface on 2.4 and 2.6 kernels. This type of sockets is used for |
7 | capture network traffic with utilities like tcpdump or any other that needs | 7 | capture network traffic with utilities like tcpdump or any other that needs |
8 | raw access to network interface. | 8 | raw access to network interface. |
@@ -44,7 +44,7 @@ enabled. For transmission, check the MTU (Maximum Transmission Unit) used and | |||
44 | supported by devices of your network. | 44 | supported by devices of your network. |
45 | 45 | ||
46 | -------------------------------------------------------------------------------- | 46 | -------------------------------------------------------------------------------- |
47 | + How to use CONFIG_PACKET_MMAP to improve capture process | 47 | + How to use mmap() to improve capture process |
48 | -------------------------------------------------------------------------------- | 48 | -------------------------------------------------------------------------------- |
49 | 49 | ||
50 | From the user standpoint, you should use the higher level libpcap library, which | 50 | From the user standpoint, you should use the higher level libpcap library, which |
@@ -64,7 +64,7 @@ the low level details or want to improve libpcap by including PACKET_MMAP | |||
64 | support. | 64 | support. |
65 | 65 | ||
66 | -------------------------------------------------------------------------------- | 66 | -------------------------------------------------------------------------------- |
67 | + How to use CONFIG_PACKET_MMAP directly to improve capture process | 67 | + How to use mmap() directly to improve capture process |
68 | -------------------------------------------------------------------------------- | 68 | -------------------------------------------------------------------------------- |
69 | 69 | ||
70 | From the system calls stand point, the use of PACKET_MMAP involves | 70 | From the system calls stand point, the use of PACKET_MMAP involves |
@@ -105,7 +105,7 @@ also the mapping of the circular buffer in the user process and | |||
105 | the use of this buffer. | 105 | the use of this buffer. |
106 | 106 | ||
107 | -------------------------------------------------------------------------------- | 107 | -------------------------------------------------------------------------------- |
108 | + How to use CONFIG_PACKET_MMAP directly to improve transmission process | 108 | + How to use mmap() directly to improve transmission process |
109 | -------------------------------------------------------------------------------- | 109 | -------------------------------------------------------------------------------- |
110 | Transmission process is similar to capture as shown below. | 110 | Transmission process is similar to capture as shown below. |
111 | 111 | ||
diff --git a/Documentation/networking/regulatory.txt b/Documentation/networking/regulatory.txt index ee31369e9e5b..9551622d0a7b 100644 --- a/Documentation/networking/regulatory.txt +++ b/Documentation/networking/regulatory.txt | |||
@@ -188,3 +188,27 @@ Then in some part of your code after your wiphy has been registered: | |||
188 | &mydriver_jp_regdom.reg_rules[i], | 188 | &mydriver_jp_regdom.reg_rules[i], |
189 | sizeof(struct ieee80211_reg_rule)); | 189 | sizeof(struct ieee80211_reg_rule)); |
190 | regulatory_struct_hint(rd); | 190 | regulatory_struct_hint(rd); |
191 | |||
192 | Statically compiled regulatory database | ||
193 | --------------------------------------- | ||
194 | |||
195 | In most situations the userland solution using CRDA as described | ||
196 | above is the preferred solution. However in some cases a set of | ||
197 | rules built into the kernel itself may be desirable. To account | ||
198 | for this situation, a configuration option has been provided | ||
199 | (i.e. CONFIG_CFG80211_INTERNAL_REGDB). With this option enabled, | ||
200 | the wireless database information contained in net/wireless/db.txt is | ||
201 | used to generate a data structure encoded in net/wireless/regdb.c. | ||
202 | That option also enables code in net/wireless/reg.c which queries | ||
203 | the data in regdb.c as an alternative to using CRDA. | ||
204 | |||
205 | The file net/wireless/db.txt should be kept up-to-date with the db.txt | ||
206 | file available in the git repository here: | ||
207 | |||
208 | git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-regdb.git | ||
209 | |||
210 | Again, most users in most situations should be using the CRDA package | ||
211 | provided with their distribution, and in most other situations users | ||
212 | should be building and using CRDA on their own rather than using | ||
213 | this option. If you are not absolutely sure that you should be using | ||
214 | CONFIG_CFG80211_INTERNAL_REGDB then _DO_NOT_USE_IT_. | ||
diff --git a/Documentation/networking/tcp-thin.txt b/Documentation/networking/tcp-thin.txt new file mode 100644 index 000000000000..151e229980f1 --- /dev/null +++ b/Documentation/networking/tcp-thin.txt | |||
@@ -0,0 +1,47 @@ | |||
1 | Thin-streams and TCP | ||
2 | ==================== | ||
3 | A wide range of Internet-based services that use reliable transport | ||
4 | protocols display what we call thin-stream properties. This means | ||
5 | that the application sends data with such a low rate that the | ||
6 | retransmission mechanisms of the transport protocol are not fully | ||
7 | effective. In time-dependent scenarios (like online games, control | ||
8 | systems, stock trading etc.) where the user experience depends | ||
9 | on the data delivery latency, packet loss can be devastating for | ||
10 | the service quality. Extreme latencies are caused by TCP's | ||
11 | dependency on the arrival of new data from the application to trigger | ||
12 | retransmissions effectively through fast retransmit instead of | ||
13 | waiting for long timeouts. | ||
14 | |||
15 | After analysing a large number of time-dependent interactive | ||
16 | applications, we have seen that they often produce thin streams | ||
17 | and also stay with this traffic pattern throughout its entire | ||
18 | lifespan. The combination of time-dependency and the fact that the | ||
19 | streams provoke high latencies when using TCP is unfortunate. | ||
20 | |||
21 | In order to reduce application-layer latency when packets are lost, | ||
22 | a set of mechanisms has been made, which address these latency issues | ||
23 | for thin streams. In short, if the kernel detects a thin stream, | ||
24 | the retransmission mechanisms are modified in the following manner: | ||
25 | |||
26 | 1) If the stream is thin, fast retransmit on the first dupACK. | ||
27 | 2) If the stream is thin, do not apply exponential backoff. | ||
28 | |||
29 | These enhancements are applied only if the stream is detected as | ||
30 | thin. This is accomplished by defining a threshold for the number | ||
31 | of packets in flight. If there are less than 4 packets in flight, | ||
32 | fast retransmissions can not be triggered, and the stream is prone | ||
33 | to experience high retransmission latencies. | ||
34 | |||
35 | Since these mechanisms are targeted at time-dependent applications, | ||
36 | they must be specifically activated by the application using the | ||
37 | TCP_THIN_LINEAR_TIMEOUTS and TCP_THIN_DUPACK IOCTLS or the | ||
38 | tcp_thin_linear_timeouts and tcp_thin_dupack sysctls. Both | ||
39 | modifications are turned off by default. | ||
40 | |||
41 | References | ||
42 | ========== | ||
43 | More information on the modifications, as well as a wide range of | ||
44 | experimental data can be found here: | ||
45 | "Improving latency for interactive, thin-stream applications over | ||
46 | reliable transport" | ||
47 | http://simula.no/research/nd/publications/Simula.nd.477/simula_pdf_file | ||