1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
menu "DCCP CCIDs Configuration (EXPERIMENTAL)"
config IP_DCCP_CCID2
tristate "CCID2 (TCP-Like)"
def_tristate IP_DCCP
---help---
CCID 2, TCP-like Congestion Control, denotes Additive Increase,
Multiplicative Decrease (AIMD) congestion control with behavior
modelled directly on TCP, including congestion window, slow start,
timeouts, and so forth [RFC 2581]. CCID 2 achieves maximum
bandwidth over the long term, consistent with the use of end-to-end
congestion control, but halves its congestion window in response to
each congestion event. This leads to the abrupt rate changes
typical of TCP. Applications should use CCID 2 if they prefer
maximum bandwidth utilization to steadiness of rate. This is often
the case for applications that are not playing their data directly
to the user. For example, a hypothetical application that
transferred files over DCCP, using application-level retransmissions
for lost packets, would prefer CCID 2 to CCID 3. On-line games may
also prefer CCID 2. See RFC 4341 for further details.
CCID2 is the default CCID used by DCCP.
config IP_DCCP_CCID2_DEBUG
bool "CCID2 debugging messages"
depends on IP_DCCP_CCID2
---help---
Enable CCID2-specific debugging messages.
When compiling CCID2 as a module, this debugging output can
additionally be toggled by setting the ccid2_debug module
parameter to 0 or 1.
If in doubt, say N.
config IP_DCCP_CCID3
tristate "CCID3 (TCP-Friendly)"
def_tristate IP_DCCP
select IP_DCCP_TFRC_LIB
---help---
CCID 3 denotes TCP-Friendly Rate Control (TFRC), an equation-based
rate-controlled congestion control mechanism. TFRC is designed to
be reasonably fair when competing for bandwidth with TCP-like flows,
where a flow is "reasonably fair" if its sending rate is generally
within a factor of two of the sending rate of a TCP flow under the
same conditions. However, TFRC has a much lower variation of
throughput over time compared with TCP, which makes CCID 3 more
suitable than CCID 2 for applications such streaming media where a
relatively smooth sending rate is of importance.
CCID 3 is further described in RFC 4342,
http://www.ietf.org/rfc/rfc4342.txt
The TFRC congestion control algorithms were initially described in
RFC 3448.
This text was extracted from RFC 4340 (sec. 10.2),
http://www.ietf.org/rfc/rfc4340.txt
To compile this CCID as a module, choose M here: the module will be
called dccp_ccid3.
If in doubt, say M.
if IP_DCCP_CCID3
config IP_DCCP_CCID3_DEBUG
bool "CCID3 debugging messages"
---help---
Enable CCID3-specific debugging messages.
When compiling CCID3 as a module, this debugging output can
additionally be toggled by setting the ccid3_debug module
parameter to 0 or 1.
If in doubt, say N.
choice
prompt "Select method for measuring the packet size s"
default IP_DCCP_CCID3_MEASURE_S_AS_MPS
config IP_DCCP_CCID3_MEASURE_S_AS_MPS
bool "Always use MPS in place of s"
---help---
This use is recommended as it is consistent with the initialisation
of X and suggested when s varies (rfc3448bis, (1) in section 4.1).
config IP_DCCP_CCID3_MEASURE_S_AS_AVG
bool "Use moving average"
---help---
An alternative way of tracking s, also supported by rfc3448bis.
This used to be the default for CCID-3 in previous kernels.
config IP_DCCP_CCID3_MEASURE_S_AS_MAX
bool "Track the maximum payload length"
---help---
An experimental method based on tracking the maximum packet size.
endchoice
config IP_DCCP_CCID3_RTO
int "Use higher bound for nofeedback timer"
default 100
---help---
Use higher lower bound for nofeedback timer expiration.
The TFRC nofeedback timer normally expires after the maximum of 4
RTTs and twice the current send interval (RFC 3448, 4.3). On LANs
with a small RTT this can mean a high processing load and reduced
performance, since then the nofeedback timer is triggered very
frequently.
This option enables to set a higher lower bound for the nofeedback
value. Values in units of milliseconds can be set here.
A value of 0 disables this feature by enforcing the value specified
in RFC 3448. The following values have been suggested as bounds for
experimental use:
* 16-20ms to match the typical multimedia inter-frame interval
* 100ms as a reasonable compromise [default]
* 1000ms corresponds to the lower TCP RTO bound (RFC 2988, 2.4)
The default of 100ms is a compromise between a large value for
efficient DCCP implementations, and a small value to avoid disrupting
the network in times of congestion.
The purpose of the nofeedback timer is to slow DCCP down when there
is serious network congestion: experimenting with larger values should
therefore not be performed on WANs.
endif # IP_DCCP_CCID3
config IP_DCCP_TFRC_LIB
tristate
default n
config IP_DCCP_TFRC_DEBUG
bool
depends on IP_DCCP_TFRC_LIB
default y if IP_DCCP_CCID3_DEBUG
endmenu
|
