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| author | Rene Mayrhofer <rene@mayrhofer.eu.org> | 2006-06-03 23:37:13 +0000 |
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| committer | Rene Mayrhofer <rene@mayrhofer.eu.org> | 2006-06-03 23:37:13 +0000 |
| commit | 42424656e873ad0da564131dbffb4b82ed3347c9 (patch) | |
| tree | 02b79fa4074fbdda73bb1953e4b54b6b918c3654 /doc/performance.html | |
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diff --git a/doc/performance.html b/doc/performance.html deleted file mode 100644 index 2258eeeda..000000000 --- a/doc/performance.html +++ /dev/null @@ -1,458 +0,0 @@ -<!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> |