[P4-dev] Why do we need header stacks?

John Grant j at ninetiles.com
Fri Dec 28 09:23:48 EST 2018


On 27/12/2018 16:44, Wu, Xiaoban wrote:
>
> Could anyone please tell me in the real-world application, in which 
> scenario would we consider using an array of header instances with the 
> same header type?
>
>
> In the P4 spec, it says "MPLS and VLAN tags are examples that might be 
> treated this way"
>
There are IP-in-IP tunnels too. In mobile networks a packet can have 
three IP headers: one which the application sees, one to route it to the 
correct cell (which changes when the phone moves to a different cell), 
and one for IPSec.

-- 
John Grant
Nine Tiles, Cambridge, England
+44 1223 862599 and +44 1223 511455
http://www.ninetiles.com

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