100G以太网姗姗将至

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新闻要点：12月5日，IEEE正式成立专为100G和40G以太网的IEEE 802.3ba，正好满足网络电视IPTV和视频网站YouTube的网络运营商带宽需求。

摘要：1，100G以太网的传输通道结构尚未定义，可能将采用4*25G或10*10G通道。2，数据中心管理者更倾向于40G网络，因为客户并不想现在就用光纤很贵的100G网络。3，目标传输距离为40公里，不同光纤运营商会应用到不同距离。4，多通道结构需要接收者均衡信号来消除失真。

5，100G和40G实体化预计2010年，互用性测试随后进行。

100-Gbps Ethernet is coming

A 100-Gbps Ethernet (100 GbE) link will require multiple transport lanes, but the channel architecture is currently undefined.

Martin Rowe, Senior Technical Editor -- Test & Measurement World, 12/6/2007 10:39:00 AM

On December 5, the IEEE formally established IEEE 802.3ba, the designation for a 100-Gbps and 40-Gbps Ethernet communications standard. Higher-speed Ethernet is being driven by our insatiable appetite for bandwidth. Much of the demand comes from on-demand IPTV, peer-to-peer video, and video-sharing Web sites such as YouTube.
A 100-Gbps Ethernet (100 GbE) link will require multiple transport lanes, but the channel architecture is currently undefined. The standard will likely specify either 4x25-Gbps lanes or 10x10-Gbps lanes, because transmitting a single lane at 100 Gbps isn’t possible with today’s technology. Specifications for both optical and electrical physical layers are likely to be developed.
Service providers will likely go for 100-Gbps links for their core networks. Data-center operators are leaning toward 40 Gbps (Ref. 1). “The people who connect servers, switches, and routers see a need for moving from 10 Gbps to 40 Gbps,” said Larry Green, chief technologist at Ixia, “but they won’t want 100 GbE right away because the optics are too expensive.”
“Ethernet is expected to map over 40-Gbps OC-768 SONET networks," added Greg LeCheminant, senior product marketing engineer at Agilent Technologies. “The IEEE high-speed study group will pursue both 40-Gbps and 100-Gbps specifications in the standard.”
Ken van Ormen, product manager at Spirent Communications, commented on transmission distances. “The goal is to get 40 km,” he said. Service providers will use the intended 10-km and 40-km links on single-mode fiber. Data centers will look at 100-m links with multimode fiber and 10-m links over copper wire or backplanes.
For several channel architectures and lengths, signal receivers will have to equalize incoming signals to compensate for transmission distortion. “You can’t look at the eye diagram of the transmitter to know what a receiver will see,” noted LeCheminant. “You have to know the channel and how the receiver must equalize the waveform.”
He expects that the transmitter waveform dispersion penalty (TWDP) test, specified in IEEE 802.3aq, may again be an important test (Ref. 2). This test requires you to capture a waveform at the transmitter and digitally process it through a simulated channel. From the results, you can calculate the distortion, or “penalty,” in the channel and design an equalizer for the receiver (Ref. 3).
The 100-GbE and 40-GbE specifications will likely be ready by the end of 2010. Interoperability testing will follow.

REFERENCES
1. Melle, Serge, John Jaeger, Drew Perkins, and Vijay Vusirikala, “Market Drivers and Implementation Options for 100-GbE Transport over the WAN,” IEEE Applications & Practice, November 2007, p. 18. IEEE Communications Society, New York, NY. www.comsoc.org.
2. Swenson, Norman L., Paul Voois, Tom Lindsay, and Steve Zeng, “Explanation of IEEE 802.3, Clause 68 TWDP,” http://ieee802.org/3/aq/public/tools/TWDP.pdf.
3. Mazzini, Marco, “Testing and Interoperability Verification of 10GBASE-LRM Optical interfaces,” www.analogzone.com/nett_050707.pdf.


FOR FURTHER INFORMATION
Presentations from the November 2007 meeting of the High Speed Study Group are available at grouper.ieee.org/groups/802/3/hssg/public/nov07/.

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