[dpdk-dev] [PATCH v5 00/12] lib: add RIB and FIB liraries

Morten Brørup mb at smartsharesystems.com
Thu Sep 12 09:37:52 CEST 2019

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Vladimir Medvedkin
> This is heavily reworked version of previous RIB library series:
> https://mails.dpdk.org/archives/dev/2018-April/099492.html
> Current lpm implementation while provides really good lookup
> performance has number of problems.
> One of them is very low speed for control plane operations
> such as add or delete a route.
> Another disadvantage is fixed number of bits for userdata
> (24 for v4 and 21 for v6)
> Also it is hard to introduce changes in existing LPM code or add new
> algorithms without breaking ABI.
> This patch series tries to solve this problems by:
> Introduce two new libraries - RIB and FIB.
> RIB that is Routing Information Base.
> It implements a control plane struct containing routes in a tree and
> provides fast add/del operations for routes. Also it allows to perform
> fast subtree traversals (i.e. retrieve existing subroutes for a given
> prefix). This structure will be used as a control plane helper
> structure
> for FIB implementation.
> Also it might be used standalone in other different places such as
> bitmaps for example.


> Second library is FIB that is Forwarding Information Base. It
> represents
> dataplane related struct and algorithms for longest prefix match.
> Internally it consists of two parts - RIB (control plane ops) and
> implementation for the dataplane tasks.
> Initial version provides two implementations for both ipv4 and ipv6:
> dummy (uses RIB as a dataplane) and DIR24_8 (same as current LPM)
> Due to proposed design it allows to extend FIB with new algorithms in
> future
> (for example DXR, poptrie, etc).

The feedback following here is meant as a comment, not an objection. Feel free to ignore!

This FIB library is designed for IP based forwarding only.

How about forwarding based on other criteria?
E.g. the FIB in a standard Ethernet switch is based on VLAN+MAC.

Such a FIB would probably require a different library, based on a hash structure, and would also require a compare-and-set function callable from the data plane in order to provide wire speed learning.

So I suggest that the documentation highlights that this FIB library is for IP based forwarding. Optionally also reconsider the name of the library and its functions, structures etc..

> From our measurements we saw 10x speedup for control plane operations
> comparing with current LPM library (depending on prefix length
> distribution)
> ToDo:
>  - introduce new performance measurement app.
>  - add documentation.
>  - add support into existing examples (l3fwd)

Med venlig hilsen / kind regards
- Morten Brørup

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