The IP path after receiving a VXLAN packet is processing the outer IP header
and not the inner one. The payload of VXLAN packet is expected to be an
ethernet packet. After VXLAN decap, the payload ethernet packet will be
processed in L2 forwarding path where no IP processing is involved.
If you want to speed up VXLAN decap processing, there is a vxlan-bypass feature
you can enable on the underlay interface which will look for VXLAN packet and
bypass IP lookup to speed up processing:
vpp# set interface ip vxlan-bypass ?
set interface ip vxlan-bypass set interface ip vxlan-bypass
<interface> [del]
Enabling this feature on IP forwarding would add slight overhead for non-VXLAN
IP packets but speed up VXLAN decap performance as IP lookup is not done.
Regards,
John
From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Zhang Yuwei
Sent: Thursday, October 18, 2018 11:26 PM
To: vpp-dev@lists.fd.io
Subject: [vpp-dev] one question IP checksum
Hi Guys and VPP maintainers,
When I run VPP in vxlan scenario, I found that when VPP receive a
vxlan packets, after decapsulation, the packet will go into ip-input node
instead of ip-input-nochecksum which means vpp will re-calculate the checksum
and verify it. I think the outer UDP checksum has already include the inner
packet as payload, so can we skip the ip header checksum calculation for inner
ip header? This part is done by software which will cause some CPU cycles
consumption and I tried if skip the checksum calculation it will have a obvious
performance gain. Can anybody give me some instructions? Thanks a lot for your
kindly help.
Regards,
Yuwei
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