Nowadays, the requirement for bandwidth in cloud data centers is increasing strikingly. To meet the demand for higher bandwidth, networking and the Ethernet industry are moving toward a new direction. Discussions previously focusing on 10GbE and 40GbE are now shifting onto 25GbE. It seems that 25GbE is more preferred and accepted by end users, which poses a threat to 10GbE and 40GbE. Why does it happen? This post will lead you to interpret 25GbE in an all-sided perspective.

25GbE—An Emerging Standard

25GbE is a standard developed by IEEE 802.3 Task Force P802.3by in July 2014, used for Ethernet servers and switches connectivity in a data center environment. The single lane design of 25GbE gives it a low cost per bit, which enables cloud providers and large-scale data center operators to deploy fewer switches and cables to meet the needs while still scaling their network infrastructure. The following table provides a summary of key upcoming IEEE standard interfaces that specify 25GbE.

Figure 1: IEEE 802.3 standard Interfaces that specify 25GbE

Cloud Will Drive to QSFP28 and SFP28

The 25GbE physical interface specification supports two main form factors—SFP28 and QSFP28. SFP28 is used for a single 25GbE port. The SFP28-25G-SR-S is an 850nm VCSEL 25GbE transceiver which is designed to transmit and receive optical data over 50/125µm multimode fiber (MMF) and support up to 70m on OM3 MMF and 100m on OM4 MMF.

The QSFP28 transceiver and interconnect cable is a high-density, high-speed product solution designed for applications in the telecommunication. The interconnect offers four channels of high-speed signals with data rates ranging from 25 Gbps up to potentially 40 Gbps, and will meet 100 Gbps Ethernet (4x25 Gbps) and 100 Gbps 4X InfiniBand EDR requirements.

Figure 2: FS.COM optical transceivers for 25GbE solution

Why Choose 25GbE

While 10GbE is fine for many existing deployments, it cannot efficiently deliver the bandwidth required by next-generation cloud and web-scale environments. And 40GbE isn't cost-effective or power-efficient in ToR switching for cloud providers. Thus, 25GbE was designed to break through the dilemma.

Number of SerDes Lanes

SerDes is an integrated circuit or transceiver used in high-speed communications for converting serial data to parallel interfaces and vice versa. The transmitter section is a serial-to-parallel converter, and the receiver section is opposite. Currently, the rate of SerDes is 25 Gbps. That is to say, we can only use one SerDes lane at the speed of 25 Gbps to connect from 25GbE card to the other end of 25GbE card. In contrast, 40GbE needs four 10GbE SerDes lanes to achieve connection. As a result, the communication between two 40GbE cards requires as many as four pairs of fiber. Furthermore, 25 Gbps Ethernet provides an easy upgrade path to 50GbE and 100GbE networks, which utilize multiple 25GbE lanes.

Figure 3: Numbers of lanes needed in different Gigabit Ethernet

Utilization of PCIe Lanes

At present, the mainstream Intel Xeon CPU only provides 40 lanes of PCIe 3.0. The lane bandwidth of a single PCIe 3.0 is about 8 Gbps. These PCle lanes are used for many connections. Therefore, it is necessary to consider the utilization of limited PCIe lanes by the network cards. Single 40GbE NIC needs at least one PCIe 3.0 x8 slot, so two 40GbE cards need to occupy two PCIe 3.0 x8 lanes. Even if the two 40GbE ports can run full of data at the same time, the actual lane bandwidth utilization is only: (40G+40G) / 8G*16= 62.5%. On the contrary, 25GbE card only needs one PCIe 3.0 x8 lane, and then the utilization efficiency is 25G*2 / (8G*8) = 78%. Apparently, 25GbE is significantly more efficient and more flexible than 40GbE in terms of the use of PCIe lanes.

10GbE vs 25GbE vs 40GbE

25GbE enables resellers and their customers to provide 2.5X the performance of 10GbE, making it a cost-effective upgrade to the 10GbE infrastructure. Since 25GbE is delivered across a single lane, it provides greater switch port density and network scalability compared to 40GbE, which is actually four 10GbE lanes. Thus, it costs less, requires lower power consumption and provides higher bandwidth. What’s more, 25GbE can run over existing fiber optic cable plant designed for 10, 50 or 100GbE and also 40GbE by changing the transceivers.

Figure 4: Bandwidth comparison for 25GbE and other Ethernet speeds

Summary

이더넷 스위치와 라우터, 수익률에서 앞서 달린다

이더넷 스위치 산업에서의 전세계 수익률이 2014년 2/4분기 기준 57억 달러로 전년대비 6.2% 성장했으며, 분기별 기준 성장률은 8.1%에 달한 것으로 나타났다. 최근 IDC 보고서에 따르면, 중국, 인도를 비롯한 아시아지역과 남미지역에서 글로벌 이더넷 스위치와 라우터 시장을 주도하고 있는 중이다. 10Gb 이더넷 스위치 포트의 출하가 큰 폭 늘어났다.

IDC의 발표에 따르면, 이더넷 스위치 산업은 일본을 제외한 아시아/태평양 지역에서 가장 높은 성장세를 구가할 전망이다. 아시아 지역은 2014년 2/4분기 기준 연간 성장률은 21%에 달할 것으로 전망된다. 중국의 경우 성장세는 40.2%에 달하고 있으며 인도의 경우는 29.3%에 달하고 있는데, 태국과 인도네시아의 경우 동기에 두 자리 수 이상의…

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Economy / cost factor will make enterprises incline to choose 40 GbE but not 100 GbE to meet its bandwidth demand increased constantly even more while building the dynamic data centre

A few days ago, Force10 network company announce plan their Ethernet ( 40 GbE) of 40 kilomegabits Integration is entered in its exchanging machine / router solution, so that the customer offers the economic scheme from 10 GbE staging to dynamic data centre.

From the intersection of server and marginal up-chain to the intersection of network and core, to data centre and the intersection of service provider and with wide demand constant growth of network, the transmission rate of Ethernet needs promoting too, and expected to get approval of IEEE one in June of this year. Force10 estimates user's consideration in economic benefits / cost will promote the arrangement carrying the end in the dynamic data centre of 40 GbE solution.

Though the development of the future market will reduce 100 GbE technical cost finally, meet server at present marginal higher the intersection of bandwidth and demand and data centre the high capacity interconnects the respect even more, the price of 40 GbE can offer the most high cost-effective.

"Excitedly, the investment of the family property inherent 40 GbE and 100 GbE will yield positive results finally as IEEE P802.3ba standard obtained approval in June in the past four years " ,Standard executive and concurrently president John D' Ambrosia of IEEE P802.3ba task set of Force10 network company show, "this standard will offer the corresponding tool to help the data centre to increase the bandwidth and reduce complexity. "

Apply 40 GbE to the solution

Though 40 GbE standard has not got approval of IEEE yet, Force10 is planning to offer the end to the central 40 GbE exchanging machine / router solution to the end, edge. First of all, Force10 plans to enter 10 GbE tank tip (top-of-rack) 40 GbE integration Insert the switchboard, in order to merge the fiber channel and network structure of the ether. In addition, E-Series core exchanging machine / router of Force10 has already supported 40/100 GbE at present, C-Series switchboard based on elastic chassis has already supported 40 GbE too at the same time. Meanwhile, through utilizing Force 10 open automation and virtual chassis, the solution of Force 10 will become strong backing of the dynamic data centre of future. Financial affairs and technology promote the factor to continue making 40 GbE become " reality " Choice

"The data that can't be halted have increased for today to adopt a great deal of questions that the data centre of 10 GbE network caused the expansibility. Though the owner of data centre wants to adopt 100 GbE, 40 GbE lower in price can lighten its financial pressure practically " ,Infonetics Research common creator and concurrently the operator and chief analyst Michael Howard of data centre network show, "with the constant improvement of the technological cost-effective, 100 GbE is significant in some aspects, but what the customer thinks at present is to simplify the network of data centre and promote the cost to drop. "

" manager and service provider of data centre are taking measures at present to simplify its network " ,Independent trade analyst and concurrently Lippis Report publisher Nick Lippis say, " even if they want to improve network performance and handling capacity, but still hope to reduce the up-chain quantity in network layer quantity and network which needs management. To 40 GbE with the staging, I/O characteristic after integration will be promoted. Can migrate from the up-chain of 4 x 10G to 2 x 40 GbE to dispose to connect, is making bandwidth while make the port quantity reduce by half. " "As to storing, calculating and the network resource will be assembled as for technical possibility of network very much in terms of bandwidth, the appearance of 40 GbE is an important step " ,Current Analysis chief analyst Steven Schuchart of data centre says, "automize on the basis of the network, virtual and merge the technical intact 40 GbE solution to contribute to reaching and realizing the equilibrium between network performance of data centre and efficiency optimized synchronously. In order to aim at satisfying data centre and enterprise of future generation this - -Especially service provider - -Concrete to be advanced in the demand one for service last foundation. "