[vpn] Cisco IPSec DES Bandwidth Overhead

[Joel M Snyder]

> 32 bytes for ESP with DES+MD5

No, definitely more than that.  Here's the breakdown:

20 octets for the IP tunnel header.
4 for the SPI
4 for the sequence number
8 for the IV (DES/3DES are the same; 64-bit IV)
some amount of padding, which may be between 0 and 7 octets
1 octet for pad length
1 octet for next header
16 octets for the ICV (hash) (HMAC-SHA1-96 or HMAC-MD5-96 are the same)

So I was wrong: it's between 54 and 61.  

I don't know where I came up with 50 to 57.  Probably counted the IV as
4 instead of 8.  It was late here... 

jms


Christopher Gripp wrote:
> 
> 32 bytes for ESP with DES+MD5
> 
>         -----Original Message-----
>         From: Andre Venter [mailto:andrev at uunet.co.za]
>         Sent: Wed 6/19/2002 10:17 PM
>         To: vpn at securityfocus.com
>         Cc:
>         Subject: [vpn] Cisco IPSec DES Bandwidth Overhead
> 
> 
> 
>         Hi All,
> 
>         Can anybody tell me what the Bandwidth overhead is, as an average percentage, when using Cisco IPSec DES Encryption between two points.
> 
>         Any info would be appreciated,
> 
>         Kind Regards
> 
>         Andre
> 
> 
>         VPN is sponsored by SecurityFocus.com
> 
> 

-- 
Joel M Snyder, 1404 East Lind Road, Tucson, AZ, 85719
Phone: +1 520 324 0494 (voice)  +1 520 324 0495 (FAX)
jms at Opus1.COM    http://www.opus1.com/jms    Opus One
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