Checking-in on Network Functions

When programming network functions, changes within a packet tend to have consequences---side effects which must be accounted for by network programmers or administrators via arbitrary logic and an innate understanding of dependencies. Examples of this include updating checksums when a packet's contents has been modified or adjusting a payload length field of a IPv6 header if another header is added or updated within a packet. While static-typing captures interface specifications and how packet contents should behave, it does not enforce precise invariants around runtime dependencies like the examples above. Instead, during the design phase of network functions, programmers should be given an easier way to specify checks up front, all without having to account for and keep track of these consequences at each and every step during the development cycle. In keeping with this view, we present a unique approach for adding and generating both static checks and dynamic contracts for specifying and checking packet processing operations. We develop our technique within an existing framework called NetBricks and demonstrate how our approach simplifies and checks common dependent packet and header processing logic that other systems take for granted, all without adding much overhead during development.Comment: ANRW 2019 ~ https://irtf.org/anrw/2019/program.htm

This is not the End: Rethinking Serverless Function Termination

Elastic scaling is one of the central benefits provided by serverless platforms, and requires that they scale resource up and down in response to changing workloads. Serverless platforms scale-down resources by terminating previously launched instances (which are containers or processes). The serverless programming model ensures that terminating instances is safe assuming all application code running on the instance has either completed or timed out. Safety thus depends on the serverless platform's correctly determining that application processing is complete. In this paper, we start with the observation that current serverless platforms do not account for pending asynchronous I/O operations when determining whether application processing is complete. These platforms are thus unsafe when executing programs that use asynchronous I/O, and incorrectly deciding that application processing has terminated can result in data inconsistency when these platforms are used. We show that the reason for this problem is that current serverless semantics couple termination and response generation in serverless applications. We address this problem by proposing an extension to current semantics that decouples response generation and termination, and demonstrate the efficacy and benefits of our proposal by extending OpenWhisk, an open source serverless platform

Recursive SDN for Carrier Networks

Control planes for global carrier networks should be programmable (so that new functionality can be easily introduced) and scalable (so they can handle the numerical scale and geographic scope of these networks). Neither traditional control planes nor new SDN-based control planes meet both of these goals. In this paper, we propose a framework for recursive routing computations that combines the best of SDN (programmability) and traditional networks (scalability through hierarchy) to achieve these two desired properties. Through simulation on graphs of up to 10,000 nodes, we evaluate our design's ability to support a variety of routing and traffic engineering solutions, while incorporating a fast failure recovery mechanism

New Directions for Network Verification

Network verification has recently gained popularity in the programming languages and verification community. Much of the recent work in this area has focused on verifying the behavior of simple networks, whose actions are dictated by static, immutable rules configured ahead of time. However, in reality, modern networks contain a variety of middleboxes, whose behavior is affected both by their configuration and by mutable state updated in response to packets received by them. In this position paper we critically review recent progress on network verification, propose some next steps towards a more complete form of network verification, dispel some myths about networks, provide a more formal description of our approach, and end with a discussion of the formal questions posed to this community by the network verification agenda