thanks ravi and alex! ravi, alex has also confirmed that the pkts are vxlan
encapsulated, outer IP would have to be the TEP IP, and inner IP is immaterial
since the slow path at the receiver would essentially ignore it.
thanks!daya
From: "[email protected]" <[email protected]>
To: [email protected]; [email protected]
Cc: [email protected]; [email protected]
Sent: Wednesday, August 26, 2015 2:28 PM
Subject: RE: [ovsdb-dev] bfd implementation in OVS
#yiv5620352777 #yiv5620352777 -- _filtered #yiv5620352777
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Daya, BFD operates on top of any data protocol (network layer,
link layer, tunnels(vxlan tunnel), etc.) being forwarded between two systems.
BFD provides failure detection on direct physical links, virtual circuits,
tunnels(vxlan tunnel) etc. If BFD is run over a VXLAN tunnel, the BFD packets
will be encapsulated inside the VXLAN header. Inner IPv4 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTL = 1 |Protocol=17(UDP)| Header Checksum
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Source IPv4 Address
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination Ipv4 Address = 127/8 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The above
picture shows a sample Inner IPv4 Header for BFD. The TTL =1 that was mentioned
in the link
(http://openvswitch.org/pipermail/discuss/2015-February/016515.html) should
corresponds to the inner IPv4 TTL. As per BFD
specification, the protocol should be run between 2 systems. 1. On a
physical network it will be between 2 links.2. On a tunnel/overlay
network, it will be between 2 end points. So, ideally the TTL value should be
1 or single hop. Consider your scenario where VXLAN is formed
between 2 OVS switches over a WAN network. How will the VM's connected to these
switches communicate? The OVS should not bother about the underlay network
and worry only about the VXLAN tunnel. In the same way, BFD will be transmitted
to the tunnel end point (TEP) over the VXLAN tunnel and consider it as a single
hop. For example consider the tunnel end points
5.5.5.1 and 5.5.5.2
From the TEP 5.5.5.1, VXLAN encapsulated BFD packet is
sent. The intermediate routers or switches should not consume the BFD packet.
Only TEP (5.5.5.2) switch should de-encapsulate the BFD packet and send it to
the BFD protocol. The BFD protocol control messages will be exchanged in this
manner. If the BFD control message are not properly exchanged between TEP’s as
per agreement, then the BFD protocol should intimate the link down to the OVS.
OVS can update it in the Physical locator table. The above said statements may
not be true for OVS implementation of BFD. I have said in the context of a
hardware switch using proprietary BFD protocol. I
think the BFD IP should be the tunnel IP, since we run BFD protocol between the
VXLAN TEP. Regards,Ravi
From: [email protected]
[mailto:[email protected]] On Behalf Of daya kamath
Sent: Tuesday, August 25, 2015 5:27 PM
To: [email protected]
Cc: Ovsdb-dev <[email protected]>
Subject: [ovsdb-dev] bfd implementation in OVS hi ,i would like some
clarification on the BFD implementation in OVS.
http://openvswitch.org/pipermail/discuss/2015-February/016515.html indicates
the BFD is not multi-hop but sent through the tunnel. can someone please
clarify, if i create a VXLAN tunnel between 2 OVS switches over a WAN,1. will
the BFD work, i.e will BFD packets be VXLAN encapsulated, and delivered as if
it were a single hop? 2. if yes, how does the OVS detect BFD payload after
stripping off the VXLAN header on an incoming packet?3. what does the VTEP put
in the inner source and dest IP fields for BFD pkts? does it put the same
values as the outer header? thanks!
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