The link quality mechanism of the MANET Neighborhood Discovery
Protocol (NHDP) enables "ignoring" some 1-hop neighbors if the
measured link quality from that 1-hop neighbor is below an acceptable
threshold, while still retaining the corresponding link information
as acquired from HELLO message exchange. This allows immediate
reinstatement of the 1-hop neighbor if the link quality later
NHDP also collects information about symmetric 2-hop neighbors.
However it specifies that if a link from a symmetric 1-hop neighbor
ceases being symmetric, including while "ignored" as described above,
then corresponding symmetric 2-hop neighbors are removed. This may
lead to symmetric 2-hop neighborhood information being permanently
removed (until further HELLO messages are received) if the link
quality of a symmetric 1-hop neighbor drops below the acceptable
threshold, even if only for a moment.
This specification updates RFC6130 "Mobile Ad Hoc Network (MANET)
Neighborhood Discovery Protocol (NHDP)", and RFC7181 "The Optimized
Link State Routing Protocol version 2 (OLSRv2)" to permit retaining,
but ignoring, symmetric 2-hop information when the link quality from
the corresponding 1-hop neighbor drops below the acceptable
threshold. This allows immediate reinstatement of the symmetric
2-hop neighbor if the link quality later improves sufficiently, thus
making the symmetric 2-hop neighborhood more "robust".
Working Group Summary
A question was raised by one participant about whether it is appropriate
to claim this work as an optimization with providing quantified measurements,
however, the working group felt that the improvements offered a quite clearly
an optimization in terms of reduced message exchanges and more rapid
recovery from transitory failures, and so no further documentation was
necessary. The consensus behind publication of this document as an
Proposed Standard RFC appears solid.
There are multiple implementations.
No MIB doctor, Media Type or other expert reviews have been done.
The Document Shepherd is Ulrich Herberg.
The Responsible Area Director is Adrian Farrel.