13. PortLand: A Scalable Fault-Tolerant Layer 2 Data Center Network Fabric

With the rapid growth of the Internet, modern computer trends are data centers with multi-core processors and end-host virtualization according to the paper. In view of the shortcomings of SEATTLE and TRILL, the authors proposed PortLand in order to make a plug-and-play-friendly environment for data center system administrators.

PortLand deals with the following issues successfully:

• Virtual Machines (VM) may migrate from one physical machine to another, and they don't need to change their IP addresses
• No switch configuration needed before deployment.
• Any end host can communicate with other hosts in the data center along any physical path.
• No forwarding loops (as SEATTLE would have when the number of hosts grow).
• Rapid failure detection.

Design of PortLand: layer 2 routing, forwarding and addressing for data center

• Fabric manager: centralized network topology, assisting ARP
• Positional Pseudo MAC Address (PMAC): provides location of the host in the topology
• Proxy-based ARP: intercepts IP2MAC and forwards to fabric manager, avoiding broadcast storm
• Distributed location discovery: applying location discovery protocol (LDP), so positioned can be changed without manual overriding.
• Provably loop free forwarding: after LDP, switches update their forwarding tables.
• Fault tolerant routing: switches informs fabric manager; fabric manager updates with the new info; fabric manager informs all affected switches

Comment: The idea of a plug-and-play data center network sounds great, but their simulation seemed to be performed locally. Is there any way it can also be used on 'cloud computing'?