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diff --git a/doc/performance.html b/doc/performance.html new file mode 100644 index 000000000..2258eeeda --- /dev/null +++ b/doc/performance.html @@ -0,0 +1,458 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> +<HTML> +<HEAD> +<TITLE>Introduction to FreeS/WAN</TITLE> +<META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=iso-8859-1"> +<STYLE TYPE="text/css"><!-- +BODY { font-family: serif } +H1 { font-family: sans-serif } +H2 { font-family: sans-serif } +H3 { font-family: sans-serif } +H4 { font-family: sans-serif } +H5 { font-family: sans-serif } +H6 { font-family: sans-serif } +SUB { font-size: smaller } +SUP { font-size: smaller } +PRE { font-family: monospace } +--></STYLE> +</HEAD> +<BODY> +<A HREF="toc.html">Contents</A> +<A HREF="interop.html">Previous</A> +<A HREF="testing.html">Next</A> +<HR> +<H1><A name="performance">Performance of FreeS/WAN</A></H1> + The performance of FreeS/WAN is adequate for most applications. +<P>In normal operation, the main concern is the overhead for encryption, + decryption and authentication of the actual IPsec (<A href="glossary.html#ESP"> +ESP</A> and/or<A href="glossary.html#AH"> AH</A>) data packets. Tunnel + setup and rekeying occur so much less frequently than packet processing + that, in general, their overheads are not worth worrying about.</P> +<P>At startup, however, tunnel setup overheads may be significant. If + you reboot a gateway and it needs to establish many tunnels, expect + some delay. This and other issues for large gateways are discussed<A href="#biggate"> + below</A>.</P> +<H2><A name="pub.bench">Published material</A></H2> +<P>The University of Wales at Aberystwyth has done quite detailed speed + tests and put<A href="http://tsc.llwybr.org.uk/public/reports/SWANTIME/"> + their results</A> on the web.</P> +<P>Davide Cerri's<A href="http://www.linux.it/~davide/doc/"> thesis (in + Italian)</A> includes performance results for FreeS/WAN and for<A href="glossary.html#TLS"> + TLS</A>. He posted an<A href="http://lists.freeswan.org/pipermail/users/2001-December/006303.html"> + English summary</A> on the mailing list.</P> +<P>Steve Bellovin used one of AT&T Research's FreeS/WAN gateways as his + data source for an analysis of the cache sizes required for key + swapping in IPsec. Available as<A href="http://www.research.att.com/~smb/talks/key-agility.email.txt"> + text</A> or<A href="http://www.research.att.com/~smb/talks/key-agility.pdf"> + PDF slides</A> for a talk on the topic.</P> +<P>See also the NAI work mentioned in the next section.</P> +<H2><A name="perf.estimate">Estimating CPU overheads</A></H2> +<P>We can come up with a formula that roughly relates CPU speed to the + rate of IPsec processing possible. It is far from exact, but should be + usable as a first approximation.</P> +<P>An analysis of authentication overheads for high-speed networks, + including some tests using FreeS/WAN, is on the<A href="http://www.pgp.com/research/nailabs/cryptographic/adaptive-cryptographic.asp"> + NAI Labs site</A>. In particular, see figure 3 in this<A href="http://download.nai.com/products/media/pgp/pdf/acsa_final_report.pdf"> + PDF document</A>. Their estimates of overheads, measured in Pentium II + cycles per byte processed are:</P> +<TABLE align="center" border="1"><TBODY></TBODY> +<TR><TH></TH><TH>IPsec</TH><TH>authentication</TH><TH>encryption</TH><TH> +cycles/byte</TH></TR> +<TR><TD>Linux IP stack alone</TD><TD>no</TD><TD>no</TD><TD>no</TD><TD align="right"> +5</TD></TR> +<TR><TD>IPsec without crypto</TD><TD>yes</TD><TD>no</TD><TD>no</TD><TD align="right"> +11</TD></TR> +<TR><TD>IPsec, authentication only</TD><TD>yes</TD><TD>SHA-1</TD><TD>no</TD><TD +align="right">24</TD></TR> +<TR><TD>IPsec with encryption</TD><TD>yes</TD><TD>yes</TD><TD>yes</TD><TD +align="right">not tested</TD></TR> +</TABLE> +<P>Overheads for IPsec with encryption were not tested in the NAI work, + but Antoon Bosselaers'<A href="http://www.esat.kuleuven.ac.be/~bosselae/fast.html"> + web page</A> gives cost for his optimised Triple DES implementation as + 928 Pentium cycles per block, or 116 per byte. Adding that to the 24 + above, we get 140 cycles per byte for IPsec with encryption.</P> +<P>At 140 cycles per byte, a 140 MHz machine can handle a megabyte -- 8 + megabits -- per second. Speeds for other machines will be proportional + to this. To saturate a link with capacity C megabits per second, you + need a machine running at<VAR> C * 140/8 = C * 17.5</VAR> MHz.</P> +<P>However, that estimate is not precise. It ignores the differences + between:</P> +<UL> +<LI>NAI's test packets and real traffic</LI> +<LI>NAI's Pentium II cycles, Bosselaers' Pentium cycles, and your + machine's cycles</LI> +<LI>different 3DES implementations</LI> +<LI>SHA-1 and MD5</LI> +</UL> +<P>and does not account for some overheads you will almost certainly + have:</P> +<UL> +<LI>communication on the client-side interface</LI> +<LI>switching between multiple tunnels -- re-keying, cache reloading and + so on</LI> +</UL> +<P>so we suggest using<VAR> C * 25</VAR> to get an estimate with a bit + of a built-in safety factor.</P> +<P>This covers only IP and IPsec processing. If you have other loads on + your gateway -- for example if it is also working as a firewall -- then + you will need to add your own safety factor atop that.</P> +<P>This estimate matches empirical data reasonably well. For example, + Metheringham's tests, described<A href="#klips.bench"> below</A>, show + a 733 topping out between 32 and 36 Mbit/second, pushing data as fast + as it can down a 100 Mbit link. Our formula suggests you need at least + an 800 to handle a fully loaded 32 Mbit link. The two results are + consistent.</P> +<P>Some examples using this estimation method:</P> +<TABLE align="center" border="1"><TBODY></TBODY> +<TR><TH colspan="2">Interface</TH><TH colspan="3">Machine speed in MHz</TH> +</TR> +<TR><TH>Type</TH><TH>Mbit per +<BR> second</TH><TH>Estimate +<BR> Mbit*25</TH><TH>Minimum IPSEC gateway</TH><TH>Minimum with other + load +<P>(e.g. firewall)</P> +</TH></TR> +<TR><TD>DSL</TD><TD align="right">1</TD><TD align="right">25 MHz</TD><TD rowspan="2"> +whatever you have</TD><TD rowspan="2">133, or better if you have it</TD></TR> +<TR><TD>cable modem</TD><TD align="right">3</TD><TD align="right">75 MHz</TD> +</TR> +<TR><TD><STRONG>any link, light load</STRONG></TD><TD align="right"><STRONG> +5</STRONG></TD><TD align="right">125 MHz</TD><TD>133</TD><TD>200+,<STRONG> + almost any surplus machine</STRONG></TD></TR> +<TR><TD>Ethernet</TD><TD align="right">10</TD><TD align="right">250 MHz</TD><TD> +surplus 266 or 300</TD><TD>500+</TD></TR> +<TR><TD><STRONG>fast link, moderate load</STRONG></TD><TD align="right"><STRONG> +20</STRONG></TD><TD align="right">500 MHz</TD><TD>500</TD><TD>800+,<STRONG> + any current off-the-shelf PC</STRONG></TD></TR> +<TR><TD>T3 or E3</TD><TD align="right">45</TD><TD align="right">1125 MHz</TD><TD> +1200</TD><TD>1500+</TD></TR> +<TR><TD>fast Ethernet</TD><TD align="right">100</TD><TD align="right"> +2500 MHz</TD><TD align="center" colspan="2" rowspan="2">// not feasible + with 3DES in software on current machines //</TD></TR> +<TR><TD>OC3</TD><TD align="right">155</TD><TD align="right">3875 MHz</TD> +</TR> +</TABLE> +<P>Such an estimate is far from exact, but should be usable as minimum + requirement for planning. The key observations are:</P> +<UL> +<LI>older<STRONG> surplus machines</STRONG> are fine for IPsec gateways + at loads up to<STRONG> 5 megabits per second</STRONG> or so</LI> +<LI>a<STRONG> mid-range new machine</STRONG> can handle IPsec at rates + up to<STRONG> 20 megabits per second</STRONG> or more</LI> +</UL> +<H3><A name="perf.more">Higher performance alternatives</A></H3> +<P><A href="glossary.html#AES">AES</A> is a new US government block + cipher standard, designed to replace the obsolete<A href="glossary.html#DES"> + DES</A>. If FreeS/WAN using<A href="glossary.html#3DES"> 3DES</A> is + not fast enough for your application, the AES<A href="web.html#patch"> + patch</A> may help.</P> +<P>To date (March 2002) we have had only one<A href="http://lists.freeswan.org/pipermail/users/2002-February/007771.html"> + mailing list report</A> of measurements with the patch applied. It + indicates that, at least for the tested load on that user's network,<STRONG> + AES roughly doubles IPsec throughput</STRONG>. If further testing + confirms this, it may prove possible to saturate an OC3 link in + software on a high-end box.</P> +<P>Also, some work is being done toward support of<A href="compat.html#hardware"> + hardware IPsec acceleration</A> which might extend the range of + requirements FreeS/WAN could meet.</P> +<H3><A NAME="11_2_2">Other considerations</A></H3> +<P>CPU speed may be the main issue for IPsec performance, but of course + it isn't the only one.</P> +<P>You need good ethernet cards or other network interface hardware to + get the best performance. See this<A href="http://www.ethermanage.com/ethernet/ethernet.html"> + ethernet information</A> page and this<A href="http://www.scyld.com/diag"> + Linux network driver</A> page.</P> +<P>The current FreeS/WAN kernel code is largely single-threaded. It is + SMP safe, and will run just fine on a multiprocessor machine (<A href="compat.html#multiprocessor"> +discussion</A>), but the load within the kernel is not shared + effectively. This means that, for example to saturate a T3 -- which + needs about a 1200 MHz machine -- you cannot expect something like a + dual 800 to do the job.</P> +<P>On the other hand, SMP machines do tend to share loads well so -- + provided one CPU is fast enough for the IPsec work -- a multiprocessor + machine may be ideal for a gateway with a mixed load.</P> +<H2><A name="biggate">Many tunnels from a single gateway</A></H2> +<P>FreeS/WAN allows a single gateway machine to build tunnels to many + others. There may, however, be some problems for large numbers as + indicated in this message from the mailing list:</P> +<PRE>Subject: Re: Maximum number of ipsec tunnels? + Date: Tue, 18 Apr 2000 + From: "John S. Denker" <jsd@research.att.com> + +Christopher Ferris wrote: + +>> What are the maximum number ipsec tunnels FreeS/WAN can handle?? + +Henry Spencer wrote: + +>There is no particular limit. Some of the setup procedures currently +>scale poorly to large numbers of connections, but there are (clumsy) +>workarounds for that now, and proper fixes are coming. + +1) "Large" numbers means anything over 50 or so. I routinely run boxes +with about 200 tunnels. Once you get more than 50 or so, you need to worry +about several scalability issues: + +a) You need to put a "-" sign in syslogd.conf, and rotate the logs daily +not weekly. + +b) Processor load per tunnel is small unless the tunnel is not up, in which +case a new half-key gets generated every 90 seconds, which can add up if +you've got a lot of down tunnels. + +c) There's other bits of lore you need when running a large number of +tunnels. For instance, systematically keeping the .conf file free of +conflicts requires tools that aren't shipped with the standard freeswan +package. + +d) The pluto startup behavior is quadratic. With 200 tunnels, this eats up +several minutes at every restart. I'm told fixes are coming soon. + +2) Other than item (1b), the CPU load depends mainly on the size of the +pipe attached, not on the number of tunnels. +</PRE> +<P>It is worth noting that item (1b) applies only to repeated attempts + to re-key a data connection (IPsec SA, Phase 2) over an established + keying connection (ISAKMP SA, Phase 1). There are two ways to reduce + this overhead using settings in<A href="manpage.d/ipsec.conf.5.html"> + ipsec.conf(5)</A>:</P> +<UL> +<LI>set<VAR> keyingtries</VAR> to some small value to limit repetitions</LI> +<LI>set<VAR> keylife</VAR> to a short time so that a failing data + connection will be cleaned up when the keying connection is reset.</LI> +</UL> +<P>The overheads for establishing keying connections (ISAKMP SAs, Phase + 1) are lower because for these Pluto does not perform expensive + operations before receiving a reply from the peer.</P> +<P>A gateway that does a lot of rekeying -- many tunnels and/or low + settings for tunnel lifetimes -- will also need a lot of<A href="glossary.html#random"> + random numbers</A> from the random(4) driver.</P> +<H2><A name="low-end">Low-end systems</A></H2> +<P><EM>Even a 486 can handle a T1 line</EM>, according to this mailing + list message:</P> +<PRE>Subject: Re: linux-ipsec: IPSec Masquerade + Date: Fri, 15 Jan 1999 11:13:22 -0500 + From: Michael Richardson + +. . . A 486/66 has been clocked by Phil Karn to do +10Mb/s encryption.. that uses all the CPU, so half that to get some CPU, +and you have 5Mb/s. 1/3 that for 3DES and you get 1.6Mb/s....</PRE> +<P>and a piece of mail from project technical lead Henry Spencer:</P> +<PRE>Oh yes, and a new timing point for Sandy's docs... A P60 -- yes, a 60MHz +Pentium, talk about antiques -- running a host-to-host tunnel to another +machine shows an FTP throughput (that is, end-to-end results with a real +protocol) of slightly over 5Mbit/s either way. (The other machine is much +faster, the network is 100Mbps, and the ether cards are good ones... so +the P60 is pretty definitely the bottleneck.)</PRE> +<P>From the above, and from general user experience as reported on the + list, it seems clear that a cheap surplus machine -- a reasonable 486, + a minimal Pentium box, a Sparc 5, ... -- can easily handle a home + office or a small company connection using any of:</P> +<UL> +<LI>ADSL service</LI> +<LI>cable modem</LI> +<LI>T1</LI> +<LI>E1</LI> +</UL> +<P>If available, we suggest using a Pentium 133 or better. This should + ensure that, even under maximum load, IPsec will use less than half the + CPU cycles. You then have enough left for other things you may want on + your gateway -- firewalling, web caching, DNS and such.</P> +<H2><A name="klips.bench">Measuring KLIPS</A></H2> +<P>Here is some additional data from the mailing list.</P> +<PRE>Subject: FreeSWAN (specically KLIPS) performance measurements + Date: Thu, 01 Feb 2001 + From: Nigel Metheringham <Nigel.Metheringham@intechnology.co.uk> + +I've spent a happy morning attempting performance tests against KLIPS +(this is due to me not being able to work out the CPU usage of KLIPS so +resorting to the crude measurements of maximum throughput to give a +baseline to work out loading of a box). + +Measurements were done using a set of 4 boxes arranged in a line, each +connected to the next by 100Mbit duplex ethernet. The inner 2 had an +ipsec tunnel between them (shared secret, but I was doing measurements +when the tunnel was up and running - keying should not be an issue +here). The outer pair of boxes were traffic generators or traffic sink. + +The crypt boxes are Compaq DL380s - Uniprocessor PIII/733 with 256K +cache. They have 128M main memory. Nothing significant was running on +the boxes other than freeswan. The kernel was a 2.2.19pre7 patched +with freeswan and ext3. + +Without an ipsec tunnel in the chain (ie the 2 inner boxes just being +100BaseT routers), throughput (measured with ttcp) was between 10644 +and 11320 KB/sec + +With an ipsec tunnel in place, throughput was between 3268 and 3402 +KB/sec + +These measurements are for data pushed across a TCP link, so the +traffic on the wire between the 2 ipsec boxes would have been higher +than this.... + +vmstat (run during some other tests, so not affecting those figures) on +the encrypting box shows approx 50% system & 50% idle CPU - which I +don't believe at all. Interactive feel of the box was significantly +sluggish. + +I also tried running the kernel profiler (see man readprofile) during +test runs. + +A box doing primarily decrypt work showed basically nothing happening - +I assume interrupts were off. +A box doing encrypt work showed the following:- + Ticks Function Load + ~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ + 956 total 0.0010 + 532 des_encrypt2 0.1330 + 110 MD5Transform 0.0443 + 97 kmalloc 0.1880 + 39 des_encrypt3 0.1336 + 23 speedo_interrupt 0.0298 + 14 skb_copy_expand 0.0250 + 13 ipsec_tunnel_start_xmit 0.0009 + 13 Decode 0.1625 + 11 handle_IRQ_event 0.1019 + 11 .des_ncbc_encrypt_end 0.0229 + 10 speedo_start_xmit 0.0188 + 9 satoa 0.0225 + 8 kfree 0.0118 + 8 ip_fragment 0.0121 + 7 ultoa 0.0365 + 5 speedo_rx 0.0071 + 5 .des_encrypt2_end 5.0000 + 4 _stext 0.0140 + 4 ip_fw_check 0.0035 + 2 rj_match 0.0034 + 2 ipfw_output_check 0.0200 + 2 inet_addr_type 0.0156 + 2 eth_copy_and_sum 0.0139 + 2 dev_get 0.0294 + 2 addrtoa 0.0143 + 1 speedo_tx_buffer_gc 0.0024 + 1 speedo_refill_rx_buf 0.0022 + 1 restore_all 0.0667 + 1 number 0.0020 + 1 net_bh 0.0021 + 1 neigh_connected_output 0.0076 + 1 MD5Final 0.0083 + 1 kmem_cache_free 0.0016 + 1 kmem_cache_alloc 0.0022 + 1 __kfree_skb 0.0060 + 1 ipsec_rcv 0.0001 + 1 ip_rcv 0.0014 + 1 ip_options_fragment 0.0071 + 1 ip_local_deliver 0.0023 + 1 ipfw_forward_check 0.0139 + 1 ip_forward 0.0011 + 1 eth_header 0.0040 + 1 .des_encrypt3_end 0.0833 + 1 des_decrypt3 0.0034 + 1 csum_partial_copy_generic 0.0045 + 1 call_out_firewall 0.0125 + +Hope this data is helpful to someone... however the lack of visibility +into the decrypt side makes things less clear</PRE> +<H2><A name="speed.compress">Speed with compression</A></H2> +<P>Another user reported some results for connections with and without + IP compression:</P> +<PRE>Subject: [Users] Speed with compression + Date: Fri, 29 Jun 2001 + From: John McMonagle <johnm@advocap.org> + +Did a couple tests with compression using the new 1.91 freeswan. + +Running between 2 sites with cable modems. Both using approximately +130 mhz pentium. + +Transferred files with ncftp. + +Compressed file was a 6mb compressed installation file. +Non compressed was 18mb /var/lib/rpm/packages.rpm + + Compressed vpn regular vpn +Compress file 42.59 kBs 42.08 kBs +regular file 110.84 kBs 41.66 kBs + +Load was about 0 either way. +Ping times were very similar a bit above 9 ms. + +Compression looks attractive to me.</PRE> + Later in the same thread, project technical lead Henry Spencer added: +<PRE>> is there a reason not to switch compression on? I have large gateway boxes +> connecting 3 connections, one of them with a measly DS1 link... + +Run some timing tests with and without, with data and loads representative +of what you expect in production. That's the definitive way to decide. +If compression is a net loss, then obviously, leave it turned off. If it +doesn't make much difference, leave it off for simplicity and hence +robustness. If there's a substantial gain, by all means turn it on. + +If both ends support compression and can successfully negotiate a +compressed connection (trivially true if both are FreeS/WAN 1.91), then +the crucial question is CPU cycles. + +Compression has some overhead, so one question is whether *your* data +compresses well enough to save you more CPU cycles (by reducing the volume +of data going through CPU-intensive encryption/decryption) than it costs +you. Last time I ran such tests on data that was reasonably compressible +but not deliberately contrived to be so, this generally was not true -- +compression cost extra CPU cycles -- so compression was worthwhile only if +the link, not the CPU, was the bottleneck. However, that was before the +slow-compression bug was fixed. I haven't had a chance to re-run those +tests yet, but it sounds like I'd probably see a different result. </PRE> + The bug he refers to was a problem with the compression libraries that + had us using C code, rather than assembler, for compression. It was + fixed before 1.91. +<H2><A name="methods">Methods of measuring</A></H2> +<P>If you want to measure the loads FreeS/WAN puts on a system, note + that tools such as top or measurements such as load average are + more-or-less useless for this. They are not designed to measure + something that does most of its work inside the kernel.</P> +<P>Here is a message from FreeS/WAN kernel programmer Richard Guy Briggs + on this:</P> +<PRE>> I have a batch of boxes doing Freeswan stuff. +> I want to measure the CPU loading of the Freeswan tunnels, but am +> having trouble seeing how I get some figures out... +> +> - Keying etc is in userspace so will show up on the per-process +> and load average etc (ie pluto's load) + +Correct. + +> - KLIPS is in the kernel space, and does not show up in load average +> I think also that the KLIPS per-packet processing stuff is running +> as part of an interrupt handler so it does not show up in the +> /proc/stat system_cpu or even idle_cpu figures + +It is not running in interrupt handler. It is in the bottom half. +This is somewhere between user context (careful, this is not +userspace!) and hardware interrupt context. + +> Is this correct, and is there any means of instrumenting how much the +> cpu is being loaded - I don't like the idea of a system running out of +> steam whilst still showing 100% idle CPU :-) + +vmstat seems to do a fairly good job, but use a running tally to get a +good idea. A one-off call to vmstat gives different numbers than a +running stat. To do this, put an interval on your vmstat command +line.</PRE> + and another suggestion from the same thread: +<PRE>Subject: Re: Measuring the CPU usage of Freeswan + Date: Mon, 29 Jan 2001 + From: Patrick Michael Kane <modus@pr.es.to> + +The only truly accurate way to accurately track FreeSWAN CPU usage is to use +a CPU soaker. You run it on an unloaded system as a benchmark, then start up +FreeSWAN and take the difference to determine how much FreeSWAN is eating. +I believe someone has done this in the past, so you may find something in +the FreeSWAN archives. If not, someone recently posted a URL to a CPU +soaker benchmark tool on linux-kernel.</PRE> +<HR> +<A HREF="toc.html">Contents</A> +<A HREF="interop.html">Previous</A> +<A HREF="testing.html">Next</A> +</BODY> +</HTML> |