We are looking for overhead accounted because of GET VPN.Is there any comparison chart or value .
Anantha Subramanian Natarajan
Packet overhead is identical to tunnel mode IPsec.
The only variation that will typically occur will be due to algorithims being used for encryption/authentication but that also applies to standard IPsec.
As mentioned by Lloyd, in GETVPN the new IP Header is a copy of the Original IP Header. So, that is going to be 20 bytes (without options). Keep in mind that the size of the packet may vary due to encryption and authentication options such as AES, SHA, etc. Roughly, around 52 to 56 bytes. So, with new IP Header you are looking at 72 to 76 bytes.
I would refer the ESP RFC 4303 for details.
I have not seen a specific GET VPN performance document on cisco.com. But, Since the Original IP Header is copied and placed in front of the ESP instead of a New IP Header like the traditional IPSEC, I dont think there is going to be much of a difference in the encryption performance between Traditional and GET VPNs.
I hope it helps.