Subject: [Speermint] Some notes on security for Speermint connections

From: Eric Rescorla <[email-masked]>
Date: Fri, 30 Jun 2006 10:33:45 -0700

I've been reading the thread about TLS and speermint with
interest and thought I'd add my $.02.

1. In Web-based TLS settings, the performance is dominated by the
   public key crypto in the handshake (typically RSA). The 
   canonical reference on this is [CDW02], which obtained
   about 250cps on a 933 MHz machine with semi-realistic
   simulated workloads. Extrapolating, a 3.8 GHz single-core
   machine would give you order 1000 cps.

2. As I understand it, this setting is mostly long-lived 
   connections so the dominating factor isn't connection setup 
   but rather throughput. Microbenchmarks show performance
   something like:

   RC4   -- 125 MB/s
   SHA-1 -- 10-116 MB/s (dependent on packet size)

3. We've run HTTPS benchmarks on large files with high rates of session
   resumption (which removes the effect of the handshake) and get
   throughputs of about 33 MB/s on low-end server class machines
   (3.0 GHz P4s running FreeBSD). For comparison, we get about
   60 MB/s running pure HTTP traffic with otherwise equivalent
   parameters. Note that this isn't perfectly realistic because
   the performance of HTTPS partly depends on record size, so if
   you're using a lot of small (< 1k, say) messages, you'd see
   inferior performance.

4. I would expect TLS and IPsec performance to be roughly 
   equivalent, provided that you used the same algorithms.
   TLS handshake performance is somewhat better because it doesn't
   require a DH exchange, but as indicated above, that cost 
   probably isn't an issue here.

   There has been some work on comparing SSL and IPsec bulk 
   performance (E.g., [AS05]), which seems to indicate that
   SSL is faster but I haven't studied the methodology
   enough to be comfortable making that claim.

Hope this helps,
-Ekr

[CDW02] Cristian Coarfa, Peter Druschel, and Dan S. Wallach, "Performance
Analysis of TLS Web Servers", Network and Distributed Systems Security
Symposium (San Diego, California), February 2002.
http://www.cs.rice.edu/~dwallach/pub/ndss2002.html

[AS05] Abdel Nasir Alshamsi and Takamichi Saito, "A Technical Comparison
of IPSec and SSL", AINA 2005. 

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