Sunday, November 2, 2014

[TTP] What is Table Type Patterns?

As we know ( if you have to deal with the multiple flow tables of OF 1.1+ ), the multiple flow tables provide the scaling capability but increasing the complex of usage. For software switch either running on hypervisor or on operation system, it can use memory to map to the implementation of such table design. But for hardware switch based on ASIC to handle packet process pipline, the forwarding pipeline and the definition of flow table is specified and fixed. That will generate a big issue: How come application running on SDN controller knows how to deal with these specified limitation. Recently I noticed "TTP", stands for Table Type Patterns, to allow for an OpenFlow controller and OpenFlow switch to agree on a set of functionality to help manage the increased diversity made possible with OpenFlow versions 1.1+. I think that is very useful for the case: OF-DPA.
This article mentions these capabilities have made OpenFlow a much more interesting tool in two major ways:

1. Better for developers. Simply put, the new features allow developers to do more interesting things: handle IPv6 traffic, provide better multipathing, and separate logical concerns into different tables. Of course, this is all limited to software switches if hardware doesn’t expose these features via OpenFlow, and it can’t do that if OpenFlow provides poor abstractions for hardware.

2. Better mapping onto hardware. The original model of OpenFlow (a single, very flexible table) was actually a poor fit for real network hardware. The new model allows for an OpenFlow table pipeline that can much more closely match the pipelines in real networking ASICs. This allows hardware to both expose more of its capabilities and expose them to controllers (and thus developers) in a way they can efficiently take advantage of.
This FAQ document give us more information in details:

TTPs will be particularly helpful in simplifying the coding of advanced OpenFlow datapath control (where many flow tables or optional functions are needed). Because TTPs describe the expected controller/switch messaging unambiguously, they will also improve interoperability.

TTPs will also be helpful in testing or benchmarking contexts where participants want advance notice to ensure conformance or optimize performance. Such participants expect precise descriptions of what messages will be used during testing or benchmarking.

To legitimately claim support for a TTP, a switch must implement all non-optional functionality described by the TTP. As mentioned above, a TTP may describe some functionality that is optional.

PS: OpenDaylight has support TTP in Helium version

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