5 bool "IP: multicasting"
7 This is code for addressing several networked computers at once,
8 enlarging your kernel by about 2 KB. You need multicasting if you
9 intend to participate in the MBONE, a high bandwidth network on top
10 of the Internet which carries audio and video broadcasts. More
11 information about the MBONE is on the WWW at
12 <http://www-itg.lbl.gov/mbone/>. Information about the multicast
13 capabilities of the various network cards is contained in
14 <file:Documentation/networking/multicast.txt>. For most people, it's
17 config IP_ADVANCED_ROUTER
18 bool "IP: advanced router"
20 If you intend to run your Linux box mostly as a router, i.e. as a
21 computer that forwards and redistributes network packets, say Y; you
22 will then be presented with several options that allow more precise
23 control about the routing process.
25 The answer to this question won't directly affect the kernel:
26 answering N will just cause the configurator to skip all the
27 questions about advanced routing.
29 Note that your box can only act as a router if you enable IP
30 forwarding in your kernel; you can do that by saying Y to "/proc
31 file system support" and "Sysctl support" below and executing the
34 echo "1" > /proc/sys/net/ipv4/ip_forward
36 at boot time after the /proc file system has been mounted.
38 If you turn on IP forwarding, you will also get the rp_filter, which
39 automatically rejects incoming packets if the routing table entry
40 for their source address doesn't match the network interface they're
41 arriving on. This has security advantages because it prevents the
42 so-called IP spoofing, however it can pose problems if you use
43 asymmetric routing (packets from you to a host take a different path
44 than packets from that host to you) or if you operate a non-routing
45 host which has several IP addresses on different interfaces. To turn
48 echo 0 > /proc/sys/net/ipv4/conf/<device>/rp_filter
50 echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
52 If unsure, say N here.
55 prompt "Choose IP: FIB lookup algorithm (choose FIB_HASH if unsure)"
56 depends on IP_ADVANCED_ROUTER
57 default ASK_IP_FIB_HASH
59 config ASK_IP_FIB_HASH
62 Current FIB is very proven and good enough for most users.
67 Use new experimental LC-trie as FIB lookup algoritm.
68 This improves lookup performance if you have a large
71 LC-trie is a longest matching prefix lookup algorithm which
72 performs better than FIB_HASH for large routing tables.
73 But, it consumes more memory and is more complex.
75 LC-trie is described in:
77 IP-address lookup using LC-tries. Stefan Nilsson and Gunnar Karlsson
78 IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999
79 An experimental study of compression methods for dynamic tries
80 Stefan Nilsson and Matti Tikkanen. Algorithmica, 33(1):19-33, 2002.
81 http://www.nada.kth.se/~snilsson/public/papers/dyntrie2/
86 def_bool ASK_IP_FIB_HASH || !IP_ADVANCED_ROUTER
88 config IP_MULTIPLE_TABLES
89 bool "IP: policy routing"
90 depends on IP_ADVANCED_ROUTER
92 Normally, a router decides what to do with a received packet based
93 solely on the packet's final destination address. If you say Y here,
94 the Linux router will also be able to take the packet's source
95 address into account. Furthermore, the TOS (Type-Of-Service) field
96 of the packet can be used for routing decisions as well.
98 If you are interested in this, please see the preliminary
99 documentation at <http://www.compendium.com.ar/policy-routing.txt>
100 and <ftp://post.tepkom.ru/pub/vol2/Linux/docs/advanced-routing.tex>.
101 You will need supporting software from
102 <ftp://ftp.tux.org/pub/net/ip-routing/>.
106 config IP_ROUTE_FWMARK
107 bool "IP: use netfilter MARK value as routing key"
108 depends on IP_MULTIPLE_TABLES && NETFILTER
110 If you say Y here, you will be able to specify different routes for
111 packets with different mark values (see iptables(8), MARK target).
113 config IP_ROUTE_MULTIPATH
114 bool "IP: equal cost multipath"
115 depends on IP_ADVANCED_ROUTER
117 Normally, the routing tables specify a single action to be taken in
118 a deterministic manner for a given packet. If you say Y here
119 however, it becomes possible to attach several actions to a packet
120 pattern, in effect specifying several alternative paths to travel
121 for those packets. The router considers all these paths to be of
122 equal "cost" and chooses one of them in a non-deterministic fashion
123 if a matching packet arrives.
125 config IP_ROUTE_MULTIPATH_CACHED
126 bool "IP: equal cost multipath with caching support (EXPERIMENTAL)"
127 depends on: IP_ROUTE_MULTIPATH
129 Normally, equal cost multipath routing is not supported by the
130 routing cache. If you say Y here, alternative routes are cached
131 and on cache lookup a route is chosen in a configurable fashion.
135 config IP_ROUTE_MULTIPATH_RR
136 tristate "MULTIPATH: round robin algorithm"
137 depends on IP_ROUTE_MULTIPATH_CACHED
139 Mulitpath routes are chosen according to Round Robin
141 config IP_ROUTE_MULTIPATH_RANDOM
142 tristate "MULTIPATH: random algorithm"
143 depends on IP_ROUTE_MULTIPATH_CACHED
145 Multipath routes are chosen in a random fashion. Actually,
146 there is no weight for a route. The advantage of this policy
147 is that it is implemented stateless and therefore introduces only
150 config IP_ROUTE_MULTIPATH_WRANDOM
151 tristate "MULTIPATH: weighted random algorithm"
152 depends on IP_ROUTE_MULTIPATH_CACHED
154 Multipath routes are chosen in a weighted random fashion.
155 The per route weights are the weights visible via ip route 2. As the
156 corresponding state management introduces some overhead routing delay
159 config IP_ROUTE_MULTIPATH_DRR
160 tristate "MULTIPATH: interface round robin algorithm"
161 depends on IP_ROUTE_MULTIPATH_CACHED
163 Connections are distributed in a round robin fashion over the
164 available interfaces. This policy makes sense if the connections
165 should be primarily distributed on interfaces and not on routes.
167 config IP_ROUTE_VERBOSE
168 bool "IP: verbose route monitoring"
169 depends on IP_ADVANCED_ROUTER
171 If you say Y here, which is recommended, then the kernel will print
172 verbose messages regarding the routing, for example warnings about
173 received packets which look strange and could be evidence of an
174 attack or a misconfigured system somewhere. The information is
175 handled by the klogd daemon which is responsible for kernel messages
179 bool "IP: kernel level autoconfiguration"
181 This enables automatic configuration of IP addresses of devices and
182 of the routing table during kernel boot, based on either information
183 supplied on the kernel command line or by BOOTP or RARP protocols.
184 You need to say Y only for diskless machines requiring network
185 access to boot (in which case you want to say Y to "Root file system
186 on NFS" as well), because all other machines configure the network
187 in their startup scripts.
190 bool "IP: DHCP support"
193 If you want your Linux box to mount its whole root file system (the
194 one containing the directory /) from some other computer over the
195 net via NFS and you want the IP address of your computer to be
196 discovered automatically at boot time using the DHCP protocol (a
197 special protocol designed for doing this job), say Y here. In case
198 the boot ROM of your network card was designed for booting Linux and
199 does DHCP itself, providing all necessary information on the kernel
200 command line, you can say N here.
202 If unsure, say Y. Note that if you want to use DHCP, a DHCP server
203 must be operating on your network. Read
204 <file:Documentation/nfsroot.txt> for details.
207 bool "IP: BOOTP support"
210 If you want your Linux box to mount its whole root file system (the
211 one containing the directory /) from some other computer over the
212 net via NFS and you want the IP address of your computer to be
213 discovered automatically at boot time using the BOOTP protocol (a
214 special protocol designed for doing this job), say Y here. In case
215 the boot ROM of your network card was designed for booting Linux and
216 does BOOTP itself, providing all necessary information on the kernel
217 command line, you can say N here. If unsure, say Y. Note that if you
218 want to use BOOTP, a BOOTP server must be operating on your network.
219 Read <file:Documentation/nfsroot.txt> for details.
222 bool "IP: RARP support"
225 If you want your Linux box to mount its whole root file system (the
226 one containing the directory /) from some other computer over the
227 net via NFS and you want the IP address of your computer to be
228 discovered automatically at boot time using the RARP protocol (an
229 older protocol which is being obsoleted by BOOTP and DHCP), say Y
230 here. Note that if you want to use RARP, a RARP server must be
231 operating on your network. Read <file:Documentation/nfsroot.txt> for
235 # bool ' IP: ARP support' CONFIG_IP_PNP_ARP
237 tristate "IP: tunneling"
240 Tunneling means encapsulating data of one protocol type within
241 another protocol and sending it over a channel that understands the
242 encapsulating protocol. This particular tunneling driver implements
243 encapsulation of IP within IP, which sounds kind of pointless, but
244 can be useful if you want to make your (or some other) machine
245 appear on a different network than it physically is, or to use
246 mobile-IP facilities (allowing laptops to seamlessly move between
247 networks without changing their IP addresses).
249 Saying Y to this option will produce two modules ( = code which can
250 be inserted in and removed from the running kernel whenever you
251 want). Most people won't need this and can say N.
254 tristate "IP: GRE tunnels over IP"
257 Tunneling means encapsulating data of one protocol type within
258 another protocol and sending it over a channel that understands the
259 encapsulating protocol. This particular tunneling driver implements
260 GRE (Generic Routing Encapsulation) and at this time allows
261 encapsulating of IPv4 or IPv6 over existing IPv4 infrastructure.
262 This driver is useful if the other endpoint is a Cisco router: Cisco
263 likes GRE much better than the other Linux tunneling driver ("IP
264 tunneling" above). In addition, GRE allows multicast redistribution
267 config NET_IPGRE_BROADCAST
268 bool "IP: broadcast GRE over IP"
269 depends on IP_MULTICAST && NET_IPGRE
271 One application of GRE/IP is to construct a broadcast WAN (Wide Area
272 Network), which looks like a normal Ethernet LAN (Local Area
273 Network), but can be distributed all over the Internet. If you want
274 to do that, say Y here and to "IP multicast routing" below.
277 bool "IP: multicast routing"
278 depends on IP_MULTICAST
280 This is used if you want your machine to act as a router for IP
281 packets that have several destination addresses. It is needed on the
282 MBONE, a high bandwidth network on top of the Internet which carries
283 audio and video broadcasts. In order to do that, you would most
284 likely run the program mrouted. Information about the multicast
285 capabilities of the various network cards is contained in
286 <file:Documentation/networking/multicast.txt>. If you haven't heard
287 about it, you don't need it.
290 bool "IP: PIM-SM version 1 support"
293 Kernel side support for Sparse Mode PIM (Protocol Independent
294 Multicast) version 1. This multicast routing protocol is used widely
295 because Cisco supports it. You need special software to use it
296 (pimd-v1). Please see <http://netweb.usc.edu/pim/> for more
297 information about PIM.
299 Say Y if you want to use PIM-SM v1. Note that you can say N here if
300 you just want to use Dense Mode PIM.
303 bool "IP: PIM-SM version 2 support"
306 Kernel side support for Sparse Mode PIM version 2. In order to use
307 this, you need an experimental routing daemon supporting it (pimd or
308 gated-5). This routing protocol is not used widely, so say N unless
309 you want to play with it.
312 bool "IP: ARP daemon support (EXPERIMENTAL)"
313 depends on EXPERIMENTAL
315 Normally, the kernel maintains an internal cache which maps IP
316 addresses to hardware addresses on the local network, so that
317 Ethernet/Token Ring/ etc. frames are sent to the proper address on
318 the physical networking layer. For small networks having a few
319 hundred directly connected hosts or less, keeping this address
320 resolution (ARP) cache inside the kernel works well. However,
321 maintaining an internal ARP cache does not work well for very large
322 switched networks, and will use a lot of kernel memory if TCP/IP
323 connections are made to many machines on the network.
325 If you say Y here, the kernel's internal ARP cache will never grow
326 to more than 256 entries (the oldest entries are expired in a LIFO
327 manner) and communication will be attempted with the user space ARP
328 daemon arpd. Arpd then answers the address resolution request either
329 from its own cache or by asking the net.
331 This code is experimental and also obsolete. If you want to use it,
332 you need to find a version of the daemon arpd on the net somewhere,
333 and you should also say Y to "Kernel/User network link driver",
334 below. If unsure, say N.
337 bool "IP: TCP syncookie support (disabled per default)"
339 Normal TCP/IP networking is open to an attack known as "SYN
340 flooding". This denial-of-service attack prevents legitimate remote
341 users from being able to connect to your computer during an ongoing
342 attack and requires very little work from the attacker, who can
343 operate from anywhere on the Internet.
345 SYN cookies provide protection against this type of attack. If you
346 say Y here, the TCP/IP stack will use a cryptographic challenge
347 protocol known as "SYN cookies" to enable legitimate users to
348 continue to connect, even when your machine is under attack. There
349 is no need for the legitimate users to change their TCP/IP software;
350 SYN cookies work transparently to them. For technical information
351 about SYN cookies, check out <http://cr.yp.to/syncookies.html>.
353 If you are SYN flooded, the source address reported by the kernel is
354 likely to have been forged by the attacker; it is only reported as
355 an aid in tracing the packets to their actual source and should not
356 be taken as absolute truth.
358 SYN cookies may prevent correct error reporting on clients when the
359 server is really overloaded. If this happens frequently better turn
362 If you say Y here, note that SYN cookies aren't enabled by default;
363 you can enable them by saying Y to "/proc file system support" and
364 "Sysctl support" below and executing the command
366 echo 1 >/proc/sys/net/ipv4/tcp_syncookies
368 at boot time after the /proc file system has been mounted.
373 tristate "IP: AH transformation"
380 Support for IPsec AH.
385 tristate "IP: ESP transformation"
393 Support for IPsec ESP.
398 tristate "IP: IPComp transformation"
402 select CRYPTO_DEFLATE
404 Support for IP Payload Compression Protocol (IPComp) (RFC3173),
405 typically needed for IPsec.
410 tristate "IP: tunnel transformation"
413 Support for generic IP tunnel transformation, which is required by
414 the IP tunneling module as well as tunnel mode IPComp.
419 tristate "IP: TCP socket monitoring interface"
422 Support for TCP socket monitoring interface used by native Linux
423 tools such as ss. ss is included in iproute2, currently downloadable
424 at <http://developer.osdl.org/dev/iproute2>. If you want IPv6 support
425 and have selected IPv6 as a module, you need to build this as a
430 config IP_TCPDIAG_IPV6
431 def_bool (IP_TCPDIAG=y && IPV6=y) || (IP_TCPDIAG=m && IPV6)
433 config TCP_CONG_ADVANCED
434 bool "TCP: advanced congestion control"
436 Support for selection of various TCP congestion control
439 Nearly all users can safely say no here, and a safe default
440 selection will be made (BIC-TCP with new Reno as a fallback).
444 # TCP Reno is builtin (required as fallback)
445 menu "TCP congestion control"
446 depends on TCP_CONG_ADVANCED
449 tristate "Binary Increase Congestion (BIC) control"
452 BIC-TCP is a sender-side only change that ensures a linear RTT
453 fairness under large windows while offering both scalability and
454 bounded TCP-friendliness. The protocol combines two schemes
455 called additive increase and binary search increase. When the
456 congestion window is large, additive increase with a large
457 increment ensures linear RTT fairness as well as good
458 scalability. Under small congestion windows, binary search
459 increase provides TCP friendliness.
460 See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
462 config TCP_CONG_WESTWOOD
463 tristate "TCP Westwood+"
466 TCP Westwood+ is a sender-side only modification of the TCP Reno
467 protocol stack that optimizes the performance of TCP congestion
468 control. It is based on end-to-end bandwidth estimation to set
469 congestion window and slow start threshold after a congestion
470 episode. Using this estimation, TCP Westwood+ adaptively sets a
471 slow start threshold and a congestion window which takes into
472 account the bandwidth used at the time congestion is experienced.
473 TCP Westwood+ significantly increases fairness wrt TCP Reno in
474 wired networks and throughput over wireless links.
480 H-TCP is a send-side only modifications of the TCP Reno
481 protocol stack that optimizes the performance of TCP
482 congestion control for high speed network links. It uses a
483 modeswitch to change the alpha and beta parameters of TCP Reno
484 based on network conditions and in a way so as to be fair with
485 other Reno and H-TCP flows.
487 config TCP_CONG_HSTCP
488 tristate "High Speed TCP"
489 depends on EXPERIMENTAL
492 Sally Floyd's High Speed TCP (RFC 3649) congestion control.
493 A modification to TCP's congestion control mechanism for use
494 with large congestion windows. A table indicates how much to
495 increase the congestion window by when an ACK is received.
496 For more detail see http://www.icir.org/floyd/hstcp.html
498 config TCP_CONG_HYBLA
499 tristate "TCP-Hybla congestion control algorithm"
500 depends on EXPERIMENTAL
503 TCP-Hybla is a sender-side only change that eliminates penalization of
504 long-RTT, large-bandwidth connections, like when satellite legs are
505 involved, expecially when sharing a common bottleneck with normal
506 terrestrial connections.
508 config TCP_CONG_VEGAS
510 depends on EXPERIMENTAL
513 TCP Vegas is a sender-side only change to TCP that anticipates
514 the onset of congestion by estimating the bandwidth. TCP Vegas
515 adjusts the sending rate by modifying the congestion
516 window. TCP Vegas should provide less packet loss, but it is
517 not as aggressive as TCP Reno.
519 config TCP_CONG_SCALABLE
520 tristate "Scalable TCP"
521 depends on EXPERIMENTAL
524 Scalable TCP is a sender-side only change to TCP which uses a
525 MIMD congestion control algorithm which has some nice scaling
526 properties, though is known to have fairness issues.
527 See http://www-lce.eng.cam.ac.uk/~ctk21/scalable/
533 depends on !TCP_CONG_ADVANCED
536 source "net/ipv4/ipvs/Kconfig"