Converged networks with Fibre Channel over Ethernet and Data Center Bridging

2
Introduction
Using application-specific networks for data, management, and storage is complex and costly. Network
convergence is a more economical solution that simplifies your data center management by partially or
completely consolidating all block-based storage and Ethernet-based data communications networks onto a
single fabric. Any network topology constructed with one or more switched network nodes is a fabric.
Converged networks consolidate two or more network types onto a single fabric.
The promise of network convergence is that it will reduce the cost of qualifying, buying, powering, cooling,
provisioning, maintaining, and managing network-related equipment. The challenge is determining the best
adoption strategy for your business.
This technology brief does the following for you:
• Defines converged networks
• Summarizes previous attempts to create them
• Explains Fibre Channel over Ethernet (FCoE) technology
• Describes how converged network topologies and converged network adapters (CNAs) work together to
tie multiple networks into a single, converged infrastructure
• Introduces the networking standards required to support this new breed of converged networks
• Explains how the new standards will affect how you will design and deploy your converged network
infrastructure over the next several years
Traditional data center topology
Traditional data centers typically have underused capacity, inflexible single-purpose resources, and high
management costs. Typical designs of data center infrastructure include separate, heterogeneous network
devices for different types of data. Each device adds to the complexity, cost, and management overhead.
Many datacenters support three or more types of networks that serve these purposes:
• Block storage data management
• Remote management
• Business-centric data communications
Multiple types of networks require unique switches, network adapters, and network management systems
and technology to unify these networks.
Early attempts at converged networks
There have been many attempts to create converged networks over the past decade. Fibre Channel Protocol
(FCP) is a lightweight mapping of SCSI to the Fibre Channel (FC) layers 1 and 2 transport protocol
(Figure1, left). FC carries not only FCP traffic, but also IP traffic, to create a converged network. The cost of
FC and the acceptance of Ethernet as the de-facto standard for LAN communications prevented widespread
FC use except for data center SANs for enterprise businesses.
InfiniBand (IB) technology provides a converged network capability by transporting inter-processor
communication, LAN, and storage protocols. The two most common storage protocols for IB are SCSI
Remote Direct Memory Access Protocol (SRP) and iSCSI Extensions for RDMA (iSER). These protocols use
the RDMA capabilities of IB. SRP builds a direct SCSI to RDMA mapping layer and protocol, and iSER
copies data directly to the SCSI I/O buffers without intermediate data copies (Figure 1, left of center). These
protocols are lightweight but not as streamlined as FC. Widespread deployment was impractical because
of the perceived high cost of IB and the complex gateway and routers needed to translate from these