Ethernet grows up -- and out
An IEEE task force is nearing completion of a standard to run Ethernet at a blistering 10 gigabits per second, which will mean an Ethernet that's not only 10 times faster, but also more widespread than ever before.
New methods for carrying native Ethernet frames over metropolitan-area networks (MAN) and WANs will enable applications that simply weren't possible before because they were too expensive to deploy, too bandwidth-constrained or both.
Those applications include everything from off-site backup, storage and disaster recovery all the way up to outsourcing your entire network.
But don't go running out to place a down payment on 10G bit/sec Ethernet just yet. The new version may look a lot like previous incarnations, but under the hood there are big differences in distance, cabling, management and network design requirements.
What's the same
Because the new specification really is "just Ethernet," your investment in Ethernet gear and in the training of your network staff is protected.
The minimum (64 bytes) and maximum (1,518 bytes) frame lengths haven't changed and the Ethernet frame format also remains in place, so a stream of 10G Ethernet frames will look the same as any other type of Ethernet.
More importantly, 10G Ethernet will carry the same traffic as any other type of Ethernet, including PBX traffic, according to Bruce Tolley, manager of emerging technologies for Cisco's enterprise business unit and vice president of the 10 Gigabit Ethernet Alliance (10GEA).
It's also important to understand what's not in the new specification. That means 10G Ethernet has no built-in facility for quality of service (QoS) or other advanced features. However, there's nothing to prevent network managers from using existing QoS features such as Diff-Serv over 10G bit/sec Ethernet.
What's different
The new version introduces numerous changes at the data-link and physical layers, including new interfaces intended specifically for MAN and WAN use.
Additionally, the new specification will run only in full-duplex mode, while every other type of Ethernet allows for half-duplex operation.
Another change that's probably welcome is that 802.3ae does not support autonegotiation, which was intended to be a convenience but in practice has proven to be a major source of connectivity headaches. The elimination of autonegotiation is likely to simplify troubleshooting.
The biggest difference is at the physical layer. Notably, the new standard will include two PHY (physical-layer) types: a LAN PHY that operates at 10G bit/sec and a WAN PHY that runs at 9.58464G bit/sec -- the same payload rate as SONET OC-192.
Seamless integration with SONET MANs and WANs was a key design goal for the IEEE task force. Even though pure Ethernet MANs are coming on strong, SONET is king in the telecom world -- and it's likely to remain so for years to come. Moving Ethernet frames over SONET networks with a minimum of disruption will help extend Ethernet into MAN and WAN usage.
To deal with the rate mismatch between the LAN and WAN PHYs, the IEEE task force defined a pacing mechanism in the media access control layer that adds enough idle signals to the interframe gap
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