Performance of scp with OpenSSH - 5.1p1

[S, Senthilprabu (NSN - IN/Bangalore)]

Hello All,
  As the release notes of SSH-4.7 version says that a new MAC algorithm
(UMAC-64 - RFC4418) was introduced with OpenSSH-4.7 which gives much
better performance, I was tempted to check out the enhanced speed
provided with new version. So I downloaded OpenSSH-5.1p1 and build it on
Solaris 10 with Sun Compiler CC.

My test setup:-
1.  Two Sunfire 440 with 2 CPU (1281 MHz) and 4GB RAM.
2.  Network interface supports 1 Gbit/s (duplex)

I tried transferring 1GB file between Node A and Node B connected using
1GB interface using SCP. Node A can connect to Node B without password
using public key authentication.

With OpenSSH-5.1p1:-
------------------------
Protocol                 Time taken  rate MB/s
Std. scp		    53.7		19.3	
scp -c arcfour 	    40.1		26.3	
scp -c blowfish 	    55.5		18.6	
scp -C 		    123.6	16.3	


With OpenSSH-4.5p1:-
-------------------------
Protocol                 Time taken  rate MB/s
Std. scp		    59.9		17.9	
scp -c arcfour 	    45		22.3
scp -c blowfish 	    59.6		17.1	
scp -C 		    131		14.1

I do not see any higher throughput (20%) with the 5.1p1 (with UMAC-64)
than 4.5p1. The above results clearly says it is not increasing the
performance by 20%. Did I something here?.
Also does UMAC-64 have a impact on scp also or my understanding is
wrong?.

Thanks inadvance
Senthil Prabu.S  

--
Senthil Prabu.S