by February 10, 2005 0 comments



Who would ever need 10 Gbps bandwidth on the network? The similar question was probably raised when 100 Mbps Ethernet was announced, and then when 1 Gigabit Ethernet came into being. So it’s likely that even 10 Gbps will be superceded. But for now, the 10 Gigabit Ethernet technology (10G) has a limited application, though important. This is the ability to offer ten times the speed of Gigabit Ethernet up to a distance of 40 Kms. It will deployed in building MANs (Metropolitan Area Networks). 

Though the communication medium for 10G is fiber, it has also been tested over copper cable, which is cost effective. However, long distance data transfers can’t be done with copper. 

Direct Hit!
Applies to:
Network managers, ISPs, research institutes 
USP: How to achieve 10 Gbps and where all can it be used
Links:
www.10gea.org 

The basic technical differences between 10G and 1 Gigabit Ethernet are the addition of a layer in the PHY (physical) layer of the OSI model, and use of a different encoding scheme, (64/66b), for better error rate detection during data transfer. Plus, 10G supports full duplex transmission only. 

So to achieve 10 Gbps, most of the changes are made in the PHY layer. 

Changes in the PHY layer 
The Ethernet standard defines two PHY types, LAN PHY and WAN PHY. 10G allows LANs in different cities to be connected over existing SONET/ SDH/TDM network using WAN PHY. Gigabit Ethernet didn’t support SONET. 

PHY layer is further divided into two sub layers, PMD (Physical Media Dependant) and PCS (Physical Coding
Sublayer). PCS is responsible for coding and
encoding data streams to and from the MAC layer, while PMD layer has been added to enable data transmission over single or multi-mode fiber.

To achieve 10 Gbps speed, XGMII interface is added between the MAC and PHY layers. The interface provides full duplex transmission between MAC and
PHY. XGMII has limitation of transferring data to larger distances. To overcome this, 10 Gigabit Attachment Unit Interface
(XAUI) is added. XAUI is a full duplex interface that uses four serial links. Each serial link gives speed of 3.125
Gbps. 

MAC
Reconciliation
Sublayer (RS)

  
XGMII
64B/66B
PCS
PMA
PMD

     
MDI

MEDIUM
10GBASE-R
  
XGMII
64B/66B
PCS
WIS
PMA
PMD
     
MDI
MEDIUM
10GBASE-W

  
XGMII
8B/10B
PCS
PMA
PMD
     
MDI
MEDIUM
10GBASE-X

XGXS (XAUI Extended Sublayer) does the conversion between XGMII and XAUI. XGMII interface is composed of four lanes of eight bits. Data flows at a speed of 3.125 Gbps in each lane. When data flows from XGMII to XAUI with clock signal, data is converted inside XGXS and encoded into data stream. The total speed achieved is 10
Gbps. The exact happens when data flows from XAUI to XGMII. 

The physical layer can be implemented either in serial or parallel configuration. Serial configuration uses one
PCS/PMA/PMD circuit, while parallel configuration has multiple PCS/PMA/PMD circuit to achieve 10 Gbps speed. 

Applications and benefits
As 10G becomes more popular, several applications could use the extra bandwidth. These include high bandwidth-intensive applications such as video on demand, distributed computing, medical imaging and scientific simulation. Universities, Research centers, enterprises having campus spread over long distance and offices spread across cities will find the technology useful. Enterprise can set up buildings at larger distances within campus and link them. This will enable extensive-bandwidth applications such as
VOIP, digital video conferencing easily accessible. Enterprise can locate their data centers, disaster recovery centers in a different city and yet get faster access.

10G will enable Network Managers to scale from 10,100, 1000 Mbps to 10 Gigabit. The cost of moving from Gigabit to 10 Gigabit will be two to three times
more, but the performance gain might be worth it. It is expected that the cost of 10G products will decrease gradually. 

Gigabit Ethernet storage servers and tape libraries are there in market. 10G will offer superior data carrying capacity compared to other storage interface technologies such as fiber channel, Ultra160 or 320 SCSI, and ATM OC-3.

10G deployments
  • World’s largest Gigabit Ethernet network was set up between Japan and Switzerland. The network stretched across 18,500 Kms and transferred the data from Japan data reservoir to CERN research center in Geneva. WAN PHY layer was used to connect LAN in University of Tokyo, with the computers in CERN. The network started in Japan and passed through Seattle, Chicago and Amsterdam before terminating in Geneva. Equipment from vendors such as Cisco, Foundry Networks and Bussan Networks were used to set the huge network. 

  • University of Southern California Information Science Institutes has deployed 10 Gigabit Ethernet network. It will enable research scientist’s high performance network for grid computing. Anna University in India has 10 Gigabit Ethernet network for its campus. 

  • Enersource Telecom, Canada provides high-speed bandwidth connections to large businesses and universities at low price. Bharti Broadband in India also has 10 Gigabit Ethernet network. 

  • Crest communication studios in India have connected two buildings together using 10 Gigabit Ethernet. This allows the artists to store and retrieve huge amount of image files from storage. 10 Gigabit Ethernet allows faster access to images, and artists can concentrate more time on production of high quality images. 

  • Several enterprises in the different sectors in India have 10G networks in place. Some of these are ISRO, Aeronautical Development Agency, ONGC and L&T.

Availability
A wide range of 10G fiber products is already available from vendors such as Cisco, 3Com, D-Link, Force 10 and Foundry Networks. Intel is the first company to have introduced 10G network interface cards (Intel PRO/10GbE) for servers. These, however, are mostly for communication over fiber. As for the copper, several vendors such as SYSTIMAX and Krone have introduced structured cabling solutions for 10G.

Sushil Oswal

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