Software Defined Networking

Software defined networking

Paper review
The Controller Placement Problem
Authors: 
Brandon Heller, Rob Sherwood and Nick McKeown
Published: 
HotSDN

Question: Given SDN topology,

  1. How many controllers are needed and

  2. where do they go?

Problems especially in WAN with long propogation delay – affects convergence and availability and informs decision as to whehter control is “real time” or pushed out to forwarding elements.

Motivating examples:

  • Internet2, placing SDN controllers in existing network

  • Aster*x distributed load balancer

  • Flowvizor centralised network slicing tool

Placement metrics:

Paper review
Outsourcing the Routing Control Logic: Better Internet Routing Based on SDN Principles
Authors: 
Vasileios Kotronis, Xenofontas Dimitropoulos and Bernhard Ager
Published: 
HotNets

Claim is for an outsourced control plane for routing which is backward compatible with BGP. Idea is that any “significant sized” networks outsource routing to a contractor specialising in this. Outsourcing party exports to contractor the following:

  • Policies, either directly or derived from SLAs.

  • Topologies and measurement data (jitter, load etc)

  • eBGP sessions – connections to other networks

Paper review
Rethinking End-to-End Congestion Control in Software-Defined Networks
Authors: 
Monia Ghobadi, Soheil Hassas Yeganeh and Yashar Ganjali
Published: 
HotNets

The central suggestion is that centrally controlled SDN networks are in a position to choose which version of TCP will work best. OpenTCP tunes TCP for traffic and network conditions. Different TCP flavours perform better at different times or in different conditions e.g. datacentre TCP (DCTCP).

Paper review
Software-defined internet architecture: decoupling architecture from infrastructure
Authors: 
Barath Raghavan, Martin Casado, Teemu Koponen, Sylvia Ratnasamy, Ali Ghodsi and Scott Shenker
Published: 
HotNets

Paper advocates decoupling of network architecture from network infrastructure – Software Defined Internet Architecture (SDIA). Problem is to allow new architectures without falling back to a “clean slate” deployment.

Defintions:

  • Architecture: “the current IP protocol or any… convention on how packets are handled”.

  • Infrastructure: “physical equipment… (routers, switches, fibre, cables etc)”

Paper review
OpenRadio: a programmable wireless dataplane
Authors: 
Manu Bansal, Jeffrey Mehlman, Sachin Katti and Philip Levis
Published: 
Hot SDN

Open Radio is a design for a programmable wireless dataplane. Wireless protocols evolve quickly and infrastructure for wireless must support this. Protocol changes are continuous but many basestations deployed. OpenRadio exposes an interface to program PHY and MAC layers. Key contributions

  1. Decouple protocol definition from hardware

  2. Abstraction layer for protocols decoupling processing and decision

Design goals

  • 20MHz processing for OFDM complexity protocols

Paper review
Logically centralized?: state distribution trade-offs in software defined networks
Authors: 
Dan Levin, Andreas Wundsam, Brandon Heller, Nikhil Handigol and Anja Feldmann
Published: 
Hot SDN

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Assumption behind paper is that control plane is decentralised but logically centralised. Physically centralised dismissed as impossible due to:

  1. responsiveness

  2. reliability

  3. scalability

Controller component choices:

  • Strongly consistent – controller components always operate on the same world view. Imposes delay and overhead.

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