100GbE_Overview_white_paper(7)

100GE以太网技术介绍

There is a further complexity associated with splitting up large aggregated flows that result from server consolidation into 10 Gbps links. Bundling multiple links is usually handled though the use of link aggregation groups (LAGs), as specified in IEEE standard 802.3ad. Shorter data

flows, such as VoIP packets, lend themselves to easy distribution across multiple links and result in efficient packing due to their small size and even flow rate. The single data flows associated with VPNs, streaming, and long-term data storage protocols are bursty in nature and cannot be split across multiple connections. Such data flows can generate bursts of up to 5 Gbps in traffic rate, resulting in high latency. ISPs often reserve bandwidth to handle maximum traffic rates without SLA penalties – resulting in low bandwidth usage. Misallocation of bandwidth can lead to dropped packets and low quality of real-time applications such as video transmissions.

Larger 40 Gbps and 100 Gbps pipes will serve to average out multiple bursty flows, resulting in higher bandwidth efficiency and lower per-Gbps costs.

Recent.Developments.and.Events

In July of 2006, the IEEE established the high speed study group (HSSG) to look into the three- to seven-year requirements for Ethernet speeds beyond 10 Gbps. The HSSG reached the conclusion that both 40 and 100 Gbps solutions should be pursued, and forwarded a project authorization request (PAR) for a higher speed Ethernet amendment to the IEEE 802.3 standard.

With approved objectives and PAR, the IEEE 802.3ba Task Force was formed in December of 2007. The task force has been meeting regularly to discuss technology proposals that are nearing finalization (expected in early 2010).

The approved task force objectives were:

Exclusive support full-duplex operation

Preserve the 802.3 Ethernet frame format using the 802.3 MAC

Preserve the current 802.3 standard minimum and maximum frame sizes

Support bit error rates better than or equal to 10-12 at the MAC/PLS service interface Provide appropriate support for optical transport networks (OTN)

Support a MAC data rate of 100 Gbps, with physical layer specifications that support operation over:

At least 40 km on SMF fiber

At least 10 km on SMF fiber

At least 100 m on OM3 MMF

At least 10 m over a copper cable assembliesThe High Speed Study Group reached the conclusions that both 100 GbE and 40 GbE solutions should be pursued.

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