Jürgen,
Juniper Business Use Only
On 12.05.24 16:05, Jeff Haas wrote:
> > bfd.PaddedPduSize:
> > The BFD transport protocol payload size is increased to this value. The
> > contents of this additional payload MUST be zero. The minimum size of this
> > variable MUST NOT be smaller than permitted by the element of BFD
> > procedure; 24
> > or 26 - see Section 6.8.6 of [RFC5880].
>
> OK. So the padding is added outside the BFD packet before any
> encapsulation.
The padded pdu is the complete encapsulated PDU, including BFD and its
transport protocol plus padding.
So, using single-hop IPv4 BFD as an example:
IPv4 header (20 bytes, e.g.)
UDP header 8 bytes
UDP payload length (padded to 9000 bytes)
BFD (24 bytes)
Thus, if you want to test 9000 byte MTU, your udp padding for this
encapsulation is:
9000 - 20 - 8 = 8972.
What you configured is 9000 since it's the total size of the padded packet.
We are not asking the users to figure out 8972. That's derived from:
- The BFD encaupsulation (UDP in this case)
- The BFD session is to an ipv4 adderss and will encapsulate in a standard IP
packet.
Similarly, consider if there's extra tunneling or ip options involved. That
will further pad the packet and thus the padding is subtracted in the UDP
layer.
> I am looking for clarity so that I know what the padding means I am
> configuring without having to dig out the specification.
Understood. "Padded packet" is intended to cover "PDUs as encapsulated to the
BFD endpoint are this size at the outer layer."
-- Jeff
