[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

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