Friday, July 1, 2016
Speaker: Pavol Cerny
Venue: IST Austria
Software-defined networking (SDN) programs must simultaneously
describe static forwarding behavior and dynamic updates in response to
events. Event-driven updates are critical to get right, but
difficult to implement correctly due to the high degree of concurrency
in networks. Existing SDN platforms offer weak guarantees that can
break application invariants, leading to problems such as dropped
packets, degraded performance, and security violations. We
introduce event-driven consistent updates that are
guaranteed to preserve well-defined behaviors when transitioning
between configurations in response to events. We propose network
event structures (NESs) to model constraints on updates, such as
which events can be enabled simultaneously and causal dependencies
between events. We define an extension of the NetKAT language with
mutable state, give semantics to stateful programs using NESs, and
discuss strategies for implementing NESs in SDNs.
Finally, we evaluate our approach empirically,
demonstrating that it gives well-defined consistency guarantees while
avoiding expensive synchronization and packet buffering.
This is joint work with Jedidiah McClurg, Hossein Hojjat, and Nate Foster.