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5   Optical Networks and their Development

Researchers have examined mainly the development of national research and education networks (NREN) and experimental research networks, such as the global TransLight and National LambdaRail networks in the USA, and the development of optical transmission systems for these networks. The acquired knowledge was applied to work on the international project SERENATE, to the development of CESNET 2 network, to the preparation of the proposal of new research intent, to the preparation of international projects GN2, GRANDE and GARDEN and to cooperation with other NRENs and to the development of CzechLight and TransLight lambda networks.

We have applied mainly the following knowledge:

1. The transfer to fibres has strategic significance. The ownership or the right to use the fibres connecting network points of presence enables the designers to choose from a much wider scale of network solutions when they are creating one, than in the case of purchase of telecommunication service. The result should be an optimal network solution which will meet the requests of the users much more sufficiently. The number of lambdas and the speed of transmission is not restricted and charged by telecommunication operators. The transmission system is not chosen by the telecommunication operator and so a better technology which is tailor-made to the network requirements can be used.
2. The use of advanced transmission technology, which in addition has configurations and parameters chosen according to the NREN users' requirements, enables much lower costs of the network construction and operation. The use of GE and 10GE transmissions instead of SDH transmissions also lowers the costs of interface circuits and requirements of telecommunication knowledge and thus decreases the costs of both the project and the operation.
3. Applied research in the field of optical transmissions is among NREN activities unusual, but it has started bringing results making it possible to build better networks. The results are immediately applicable to the transfer of NREN to fibres.
4. The method of realisation of optical lines without in-line equipment - if it is possible - which has been introduced at TERENA conference in Limerick in 2002, has become known under the name "NIL approach" (Nothing In Line) and has turned out as very suitable for NREN. This is caused mainly by relatively short distances between university workplaces, their ability to locate the equipment in their premises and to provide local assistance in necessary cases, while the equipment is remotely monitored and set from the network centre.
5. We expect that in near future the use of PCs with optical transceivers GE and 10GE of small size (XFP MSA) and long reach (80-130 km) supported by programmable hardware (such as COMBO6 card) for higher throughput and, if need be, completed with the equipment for optical amplification (prolonging the optical reach to double distance) or coloured transmissions (WDM), will be significant for the construction of NRENs.
6. We expect the rise of open hardware systems. Open software systems (e.g. Linux, Globus) successfully compete with products of giant companies (e.g. Microsoft and IBM) because they follow open worldwide research and development cooperation of organizations and citizens on their perfection and because they provide users with wide possibilities of adapting the systems effectively so that they meet the users' requirements.But at the same time, the supply of routers, switches and transmission systems for the Internet and also the supply of devices and instruments for many other branches is very much monopolized and there is no competition in open solutions for them yet. This makes the prices very high, restricts the possibilities of development and discourages from the applications with special requirements of safety, security of personal data, price, etc.

The transfer of CESNET2 production network to fibres was in the main completed in 2003. In January 2004, NREN in the Czech Republic is going to have 2,354 km of operating double-fibre lines and 360 km of single-fibre lines, which is the total of 2,714 km to approximately 10.2 mil people and 78,866 km² of area. For comparison we note that the most advanced countries in applying fibres in Europe are Poland, Slovakia and Switzerland. For NREN, Poland has its 2,600 km of fibre to 38.7 mil people and 312,683 km² of area, in Slovakia NREN has its 1,370 km of fibre operating to 5.4 mil people and 49,035 km² of area, in Switzerland it is 1,200 km of NREN's operating fibre to 7.3 mil people and 41,293 km² of area. Next fibres are in most cases being prepared for use or they are booked. In other European countries, the use of fibres for NREN is lower, in some of them the transition to fibres is still being considered. In GÉANT network fibres are not used. In the USA, the dedicated fibres for the national production network (Abilene2) are not used but the use of fibres for the national production networks of individual states of the union is very frequent and 2,600 miles of fibres are booked for the national experimental network National LambdaRail with the possibility of the network's widening (only a small part is now in operation).

In the Czech Republic, we have preferred transformation of the CESNET2 production network on fibres in consequence of price level. We have started preparation of intercity fibre connection for CzechLight in end of year 2003. For year 2004, international fibre lines between Prague and Vienna and between Prague and Poznań (see Figure) is prepared; realisation depends on cooperation and support from our partners, Cisco Systems an EU.

5.1   Intention of the Research and Development of Optical Networks and the Main Results

The researchers have focused on the following activities and they have reached the following main results:

1. The transition of the main lines of CESNET2 network to leased optical fibres which enables the development of transmission parameters of the network independently of the providers of telecommunication services. The use of the fibres gradually puts its way through in the world as the way of NREN perfection and the Czech Republic belongs to the first countries engaged. The results in the reconstruction of CESNET2 network have been reached thanks to the cooperation with the network development and operation team.
2. The lease of the fibres including the transmission facilities is for NREN in the Czech Republic much more advantageous than the purchase of gigabit telecommunication service. Moreover, a favourable situation and well-specified tenders for the fibre leasing lead to price decrease by 50-75 %.
3. The decrease in prices made it possible to change the topology of the network so that the access to the nodes is better (backbone nodes are accessible by means of at least two gigabit circuits) and the reliability of the provided service is much higher.
4. Gaining the option of the realization of the fibre first mile to the members' workplaces to order (which is now among NREN unusual); physical access of the most important nodes of CESNET2 network by fibres of 3-4 different owners.
5. Economically effective connection of the members in Děčín , Cheb, Jindřichův Hradec, Karviná and Opava by means of single fibre lines. At the same time, it is a step forward to decrease the difference between the access to information service and the chances of attending contemporary projects of the research and development among Czech regions.


Figure 5.2: CESNET2 topology (December 2003) (large image)

6. Creating the first NRENs connection in Europe by means of dark fibre (Brno-Bratislava); gaining similar offers from Vienna, Munich, Frankfurt a. M., Nurnberg, Dresden, Berlin, Poznań and Bielsko-Biala. Some of them will probably be used for the international projects GN2 JRA4 and GARDEN.
7. Lowering the prices of the lease of the fibres also enabled the start of the construction of CzechLight network (which is of experimental character) physically separately from CESNET2 network providing production service - similarly to TransLight and National LambdaRail, which are physically separated from Abilene, GÉANT and NREN. This has opened significant new chances of research in this area for the researchers. It is known that the chances of research of new transmission systems and services on production networks are very much limited.
8. Setting up lambda service Prague-Amsterdam 2.5 Gbps, installation and testing CzechLight, finding the errors of the equipment and complaint of them. Lambda services CzechLight, NetherLight and CERN have been experimentally used for the transmission of data between CERN and ASCR Institute of Physics (IoP) at Mazanka, Prague. Also Prague Academic Network (PASNET), ASCR (Academy of Science of the Czech Republic) - network of Na Mazance area - and IoP local network have been involved in realization of this end-to-end service.
9. Gaining the possibility of financially reasonable upgrade of the circuit Prague-Amsterdam from 2.5 Gbps to 10 Gbps and thus gaining more interest or acceptability for experiments shared with institutions in Europe, the USA, Canada and for presentation of the results.
10. Simulations and testing of the setting of optical amplifiers EDFA for GE and 2.5 Gbps transmissions without in-line equipment up to approximately 250 km; putting it on the operational line of 235 km (which is probably the world's primacy in production network).
11. Simulation and testing of the setting of optical amplifiers EDFA for 10GE transmissions without in-line equipment up to 250 km long line (the reach supposed by 10GE standard is up to 40 km). Testing of optical amplifying of WDM transmissions. Cisco company has been interested in cooperation in optical transmissions development.
12. Testing of Raman amplifiers for prolonging the distances noted above.
13. The presentation of the results in setting up dark fibres and testing the possibilities of transmission systems, participation in the preparation of GN2, GRANDE and GARDEN projects.
14. The proposal of setting the fibre line Prague-Frankfurt with optical amplifiers as the base for DANTE, simulation of running of the signals, consultation to "Invitation to Tender for Network Element for the GN2 Network".
15. Evaluation of the situation in the area of wireless microwave and optical transmissions (mainly 802.11a and 802.11h) from the view of their usability for the first mile of inter-city transmission circuits. The preparation of the prototype of the equipment for free space optical transmissions 100 Mbps, the first result may be expected by the end of the year 2003.
16. The testing of the possibility of building the regenerator for optical fibre transmissions by programmable hardware is running through.
17. The work on replacement of expensive transmission equipment or interface cards and independent optical amplifiers by equipment with FPGA, XPF, transceivers, circuits for optical amplification, ASIC and hybrid IO is running through. The advantage should be Open hardware and remarkably lower price.

When solving the project, we have reached the results recognized abroad (see the list of publications and presentations).

5.2   Cooperation of NRENs on Setting Dark Fibre

We presented the results of CESNET2 network design and operation at international seminars TF-NGN in February 2003 in Rome and in September 2003 in Cambridge. These presentations and following discussions helped us to make contact with experts from individual NRENs which deal with fibre lines and transmission systems procurement and implementation. By the end of the year 2003, for active participants we have started international mailing list CEF-Networks for support of dark fibre implementation in European NRENs. Reciprocal consultations about dark fibre implementation ran through mainly with our colleagues in Ireland, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Serbia and Switzerland. The aim is above all to gain and widen information about the ways of acquirement of fibre lines and the solutions of transmission systems which have been proved on experimental or operational NREN lines. It's turned out recently that this effort will even be supported by international GN2 project (Joint Research Activity 4 - Testbed) of the FP6 program of the EU.

5.3   National Fibre Footprint

In the USA, the project called National LambdaRail (NLR) rose in 2003. This project contractly uses some of the fibres of Level 3 company (see Figure) and cals them National Fibre Footprint. This infrastructure extends the fibres used in individual states and regions in research and education networks in the USA. This has significantly strengthened the focus on the use of fibres in research and education networks, which was not so much used before. GN2 project in Europe now is trying to find out to what extend fibres are suitable for the pan-European network.

In the Czech Republic, the national fibre footprint of the CESNET2 production network is already in operation.

At the end of 2002, we announced a tender for setting up and lease of fibres for seven backbone circuits. Only the routes Plzeň-České Budějovice and Ústí nad Labem-Liberec were selected for realization. Other circuits were not recommended for realization, mainly due to too long fibres or unacceptable requirements of the tenderers. The circuits were much cheaper than the service used till then. We also gained the possibility to use free of charge testing loops of fibres of various length for testing transmission systems in the laboratory. In March 2003, we announced a tender for setting up and lease of fibres for nine routes, out of which seven were backbone lines. The aim of this tender was not setting up new lines but replacement of the existing ones - with better conditions, not only from financial but also from technical point of view. This means acquiring fibres with better parameters (e.g., shorter lines with lower attenuation) and lines which use at least partly G.655 fibre.

The lease of the fibres was offered by eight competitors, two of them had been refusing fibre lease before. The prices of leased fibres for NREN are lower than 1.25 CZK/m/pair/month (about 0.5 EUR/pair/m/year), in some cases they are much lower. There has mainly been decrease in prices of routes between main regional cities where the fibres of the providers remain unused for a longer time. When evaluating the offers, we were searching for an optimal solution with respect not only to the price but also to the length of fibres and necessary HW for transmission. On longer routes, the purchase of amplifiers is necessary and thus the technical and operational requirements of the route grow.

What has been an essential knowledge gained during the solution is how to specify tender for fibres and what criteria to choose so that the realized network is of top parameters and keeps open possibility of further development for attainable financial resources. CESNET2 network now has the fibre footprint longer than 2,000 km, low expenses on its lease and wide scale of possibilities of increasing transmission speeds and capacities (see Figure).

5.4   Optical Transmissions in Customer Empowered Fibre Networks

Customer Empowered Fibre networks (CEF networks) are networks where (some of) the users of the network own the fibres or have the right to use the fibres and to decide the way of the network design (mainly the transmission system) and network operation.

Gaining the fibres is followed by the question how to solve the transmission system best. Of course, offers of transmission systems for telecommunication operators may be used but these are usually very expensive. It also turns out that NRENs have different requirements and so it is often most acceptable to build a "tailor-made" transmission system and upgrade it to higher transmission speed or higher number of lambdas at the time when it's really necessary.

It is also important to figure that the prices of fibres and equipment change (now are decreasing very significantly) and so it is economically very risky "to build for future needs". Moreover, the uncertainty connected with future needs often results in the selection of more universal solutions which are usually more expensive. Sometimes it is more profitable to rent another pair of fibres than to invest into the transmission equipment. According to what is feasible for us, we have dealt with the analysis of this situation and evaluation of the individual methods of solutions and we have proved some of them in laboratory or in CESNET2 production network.

5.4.1   Transmission Routes without In-Line Equipment

One of the significant methods of CEF network setup is NIL which is trying to solve the topology of the network so that it is not necessary to use in-line optical amplifiers or regenerators. This means that all devices are located in PoPs of the network. Figure shows to what extent this method is applied in CESNET2 network. Dark blue routes are fibres without in-line equipment, i.e., NIL fibres. The transition of the remaining light blue and red routes (except for the route Prague-Brno) to this way of transmission should be carried out by the end of January 2004.

5.4.2   Single Fibre Transmission

CESNET has used new types of converters which implement bi-directional transmission over one optical fibre for economically effective connection of sites of members or some of the customers.

We opted for new single-fibre lines using tested twisted pair-fibre converters made by MRV (e.g., http://www.mrv.com/product/MRV-FD-FS). This way is economic and technically attractive. It is possible to implement the transmission for Ethernet, Fast Ethernet (FE) and Gigabit Ethernet. The converters are made for transmission over single fibre and pair of fibres. Equipment for transmission over single fibre has shorter reach. We opted for two-way transmission over a single fibre, using different wavelengths 1520 nm and 1560 nm for different directions. According to the available information, this transmission system is more reliable than the system that uses of the same wavelength for transmission in both directions.

During the year 2003 we deployed five single-fibre lines with FE converters. We obtained leasing of one fibre under 60 % of price of leasing pair of fibres for five-year contract from one provider. We didn't manage to obtain the leasing of one fibre from other providers because the demand for these fibres is still quite low and the second fibre from the pair remains unused. This situation might change when one fibre transmission in both directions becomes better known.

At the end of March 2003 we launched the first operational long-distance line Ostrava-Opava. The distance is 55 km and we used MRV converters EM316 WFC/S4 & MRV EM316 WFT/S4 (formerly Nbase-Xyplex) for Fast Ethernet for both ends of line. The operation on this line is error-free. The independence of the converters on the Cisco Systems equipment, software and support is a great advantage.

We used the same model with S4 converters for two other lines, Ostrava-Karviná and České Budějovice-Jindřichův Hradec. The pair of S3 converters with the reach 20-50 km sufficed for the shortest line Ústí nad Labem-Děčín. We deployed the S5 converters for the longest line Plzeň-Cheb with its distance of 126.4 km and attenuation 35.7 dB. After deployment the line was working without errors for one month although the parameters of the line are worse then those specified by the converter provider. This result we consider interesting in spite of the fact that it originally occurred due to low financial resources for purchase of device. After one month the line error rate raised and it was necessary to switch the traffic to the old line. The measurement of this line demonstrated that the parameters of the fibre had not worsened. We found out during the test that this pair of converters had higher error rate on shorter line too. This means that there was error on the equipment. The S4 converters on the line Ostrava-Karviná had a breakdown too. The result is the complaint of the fault of the device, purchase of the pair of S3 converters for elongating of reach on the line Plzeň-Cheb and purchase of spare converters for the case of the fault on some single-fibre line. Despite these problems with reliability of some MRV equipment, single-fibre lines seem to be the most advantageous solution in a specific situation.

Fast Ethernet is operational on all single-fibre lines. These lines are suitable for transmission speed 100 Mbps. It is also possible to equip them with the converters of Gigabit Ethernet, but it does not seem necessary in consideration of the workload now. On the whole, single-fibre lines are financially comparable to microwave circuits but they are faster and more reliable. The difference in reliability is more significant on longer lines. Long microwave lines are sensitive to atmosphere troubles. The exception which is financially not very favourable is when it is necessary to lay long segment of fibre (principally first mile). The payoff of the investment to MRV converters is very good. The longer the line, the more favourable is the investment.

Deployment of the 10GE technology on a single fibre: At our request, PASNET (Prague Academic and Scientific network) has experimentally built and tested the interconnection between the ASCR Institute of Physics at Mazanka (IoP) and the office of CESNET Association at Zikova.

For the high-speed transmission to the remote sites of their cooperating partners outside the Czech Republic, the ASCR Institute of Physics uses the international lambda services provided by CESNET from the Zikova location in Prague. The link between the Institute's premises at Mazanka and the CESNET site at Zikova is provided by the PASNET.

IoP's computers at Mazanka are connected to a Gigabit switch from Cisco Systems. This switch is connected to the backbone device Catalyst 6509 at Ovocný trh location with a single single-mode fibre (7 km length), using the 1000BASE-SX GBIC module (product designation WS-G5484) and converters from MRV. From Ovocný trh, the service continues as a specific VLAN through PASNET's 10 Gbps backbone link to Catalyst 6506 at Zikova location with 802.1Q protocol. The link terminates on the ONS 15450 device at the CESNET centre.

Based on economic considerations, we have opted for the solution with optical converters to minimize operational costs. We deployed MRV's protocol-independent converters, product designation EM316WGC-T. These converters use different wavelengths (1310/1550 nm) for either direction of communication on a single fibre. According to the documentation, this type can be used for the distances up to 25 km.

It is worth mentioning the fact that the backbone line of the Prague academic network (an SM segment of 5 km) between locations Ovocný trh and Zikova was also operating with passive splitters on a single fibre for the period of three months. The technology was 10GE between Catalyst switches (modules WS-X6502-10GE fitted with WS-G6488-10GBASE-LE, i.e., using the wavelength of 1310 nm). Converters EM316SC3S were used as suitable for this wavelength. There was neither deterioration of service nor increase in error rate resulting from the use of optical splitters.

There was no unscheduled outage on the above described link IoP Mazanka-Zikova throughout the whole period of six months when the service was used.

We were looking for the best solution in realization of single-fibre inter-city circuits, but we detected among other NRENs only one. Swiss network SWITCH (The Swiss Education & Research Network) is using an interesting solution for the cheap single-fibre long-distance connections, which has been used for more than one year. For bidirectional Gigabit Ethernet, the Cisco CWDM GBICs are used in the routers and the POCs - Passive Optical Couplers - on both ends of single fibre. The equipment POC consists of the splitter for two wavelengths (1530 and 1550 nm) and OADM-1 Channel Optical Add/Drop Multiplexer. OADM takes out the reflections due to bad connectors and fibre impurities.

Without another amplifiers the distances up to 100 km were achieved. With the help of EDFA amplifiers (16 dBm) - between the output of GBIC and POC - the distances up to 150 km are reachable.

SWITCH has the leased pairs of dark fibres in use, but after the tender and selection procedure it is using the transfer equipment Sorento (for single fibre) for the backbone lines. The second fibre is verywell used for connecting other institutions along the lines. The topology of SWITCH is shown in Figure.

5.4.3   Simulations, Testing and Deployment of GE NIL Long-Haul Transmissions

In the area of optical signal amplification we have taken up with our knowledge made back in 2002, when line Praha-Pardubice with the length of 189 km was put into service. This year, another NIL line Brno-Ostrava with the length of 235 km was put into service. With the use of Gigabit Ethernet (GE) as transport protocol, it was possible to deploy high-power erbium doped fibre amplifiers (EDFA) only. We were able to test 2.5 Gbps PoS, too. In this case it was necessary to deploy additional EDFA preamplifiers (the reason is lower sensitivity of PoS line cards). A migration to PoS technology did not occur yet and the line works error-free. As far as we know, no line with similar parameters is operated in any other network (neither research nor production).

With standard CWDM GBIC it is possible to overcome distance up to 250 km, which we verified in lab environment on G.652 spools kindly loaned by OFS, Denmark (former Lucent). Detailed schemes of tested configurations are to be found in Annual Research Report 2002.

5.4.4   Simulations, Testing and Deployment of 2.5 Gbps NIL Long-Haul Transmissions

Nowadays, optical amplifiers are used on the following backbone lines: Praha-Plzeň, Plzeň-České Budějovice and Brno-České Budějovice. On the first line, two 10 dBm EDFA amplifiers are used in non-typical configuration: one amplifier is used as a preamplifier and the other one is used as a booster. This brings the advantage of placing both of them in Praha, which means that deployment and maintenance of the amplifiers is easier. The second line with the length of 178 km is equipped with boosters only.

The line Brno-České Budějovice has length 308 km and to keep NIL approach, EDFAs are not sufficient and one has to utilize an amplification effect based on the principle of stimulated Raman backscattering (RFA). Some problems occurred within delivery of Raman amplifiers and we tested the amplifiers in our lab together with G.652 spools from OFS at the beginning of December. In agreement with the results of simulations and experiments, it is possible to equip the line by means of NIL method before the end of 2003 (for every direction, it is necessary to deploy one EDFA booster and one EDFA preamplifier, Raman fibre laser and optical filter to suppress the noise). For some time, due to these reasons, the line is equipped with EDFA amplifiers only, one of them works as booster and the other one works as in-line amplifier. The line works error-free in this configuration. 2.5 Gbps technology was tested in the lab in configuration with in-line amplifiers up to distance 350 km, and no compensation of chromatic dispersion or the use of optical filters to suppress the noise was necessary.

5.4.5   Field Trial with 10 Gigabit Ethernet Adapters for PC

We have acquired two 10 Gigabit Ethernet adapters for PC (Intel PRO/10GbE) for measurement and experimental work in the SCAMPI project and for evaluation of issues in end-to-end 10 Gigabit Ethernet communication. As a first step we tested achievable throughput with Linux PC and estimated the maximum possible distance between the sender and receiver. We described our observations in CESNET technical report 10/2003. We summarize here some of our findings.

Test Setup

The test setup is shown in Figure. Each adapter was installed in a PCI-X 64-bit 133 MHz slot of a Dell 2650 server. This slot has its own PCI bus, that is no other device shared the same PCI bus. The server was equipped with one Intel Xeon 2.4 GHz processor and 1 GB RAM. The two adapters were connected back-to-back with a short optical patch cable. Both machines ran Debian Linux with 2.4.22 kernel.

Optical Power Budget

The Intel PRO/10GbE LR adapter uses a 1310 nm laser with the specified reach of 10 km. Unfortunately, the transceiver is of the "300-pin" type and cannot be replaced with another transceiver (such as one using a 1550 nm laser, which would be an attractive option), which is possible with XFP or XPAK type transceivers.

The output power measured by the Expo FOT-90A fibreoptic power meter was -3.2 dBm on one adapter and -5.0 dBm on the other adapter. We inserted the Expo FVA-60B variable attenuator between the two adapters to find the maximum acceptable power budget between the sender and receiver. We found that the maximum acceptable attenuation with no packet losses was 7.85 dB in one direction and 8.30 dB in the other direction. Taking the lower value and considering attenuation of 0.35 dB/km at 1310 nm on standard optical fibres, we can estimate the maximum possible distance between the sender and receiver to approximately 22 km.

Interconnection with 1550 nm Devices

High-speed optical ports on routers and switches use 1550 nm lasers more frequently than 1310 nm lasers. The reason is most optical fibres have lower attenuation at 1550 nm and the signal at this wavelength is also easier to amplify, which allows to span longer distances. It is important for high-speed ports, which are usually used for long-distance backbone circuits. On the other hand, PC adapters are usually designed for use in local networks and are therefore often equipped with cheaper 1310 nm lasers. In this case, for end-to-end communication over a wide-area network we need to resolve how to connect 1550 nm and 1310 nm devices together.

Optical wavelength converters are not yet commercially available. We can expect that if such a device becomes available, it will be expensive. We can however take advantage of broadband sensitivity of most optical receivers. We tried to connect the Intel PRO 10GbE LR adapter directly to the Cisco Catalyst 6500 switch with the WS-X6502-10GE 1-port 10 Gigabit Ethernet adapter, which uses an extended reach 1550 nm laser. The 1-port adapter has a fixed non-interchangeable transceiver, unlike the more expensive 2-port and 4-port adapters, which use XENPAK type interchangeable transceivers.

A 5 dB attenuator was inserted in each direction to protect the receiver from a possible damage by a high power level from the sender (it was actually needed only in the direction from the extended reach laser). Communication worked without any problem and we successfully sent and received 6 millions of 1500-byte packets, that is 3.6×10¹¹ bits without any packet loss or damage. This shows that the Intel PRO 10GbE LR adapter can be reliably used to connect to the Catalyst's 1550 nm transceiver, thus enabling an end-to-end 10 Gigabit Ethernet communication over a wide-area network.

Throughput

We used iperf to measure TCP throughput. Both sender and receiver socket buffers were set to 1 MB. Transmission interface queue (txqueue) was set to 10,000 packets. This value was computed using a rule of thumb that it should cover transmission at the physical interface rate (10 Gbps) for the duration of the operating system scheduling timer (10 ms). PCI-X burst transfer size was increased from the default value of 512 bytes to 4096 bytes. We used a standard MTU of 1500 bytes and the maximum MTU of 16,114 bytes supported by the adapters. We also monitored CPU load with the top command and the number of generated interrupts by reading the /proc/interrupts file before and after the test.

We have measured throughput of 1.3 Gbps for 1500-byte packets and 2.6 Gbps for 16,114-byte packets. In the latter case, the sender CPU load was almost 100 %. The receiver CPU load as well as the load on both sides with 1500-byte packets were lower and did not limit the achieved throughput. The CPU load increased probably as a consequence of significant increase in number of interrupts. It appears that interrupt coalescing did not work properly.

Conclusion

We achieved the maximum TCP throughput 2.6 Gbps with 16,114-byte packets on Dell 2650 servers. If the problem with interrupt coalescing is resolved, the achieved throughput could probably be higher. However, the use of jumbo packets (larger than 1500 bytes) is required to achieve throughput significantly higher than 1 Gbps.

The maximum acceptable power budget should allow communication up to approximately 22 km. Interconnection with 1550 nm transceiver on Cisco Catalyst switch worked without problems. This enables an end-to-end 10 Gigabit Ethernet communication over a wide-area network (although not at the full speed with current PCs).

The adapters could be also used to build a relatively inexpensive 10 Gigabit Ethernet router or switch, with multiple adapters in one PC running proper routing or switching software. With current PCs, the throughput would be however much lower than the full line rate. Another possible use is for emulating fast long-distance networks with NIST Net network emulator.

5.4.6   Simulations and Testing of 10 Gbps NIL Long-Haul Transmissions

In the first half of the year, we were evaluating performance limits of NRZ data transmission at 10 Gbps over standard single mode fibre (SMF, G.652) without the deployment of in-line EDFAs with the aim to find out the limits of the maximum transmitter-receiver distance and to keep the bit-error-ratio (BER) below 10^-12. For these numerical simulations we used commercial software OptiSystem 2.0 from OPTIWAVE and software OptSim from ARTIS.

The effect of input optical powers to SMF and to the dispersion compensating fibre (DCF), degree of GVD compensation of the SMF, and the effect of group velocity dispersion (GVD) compensation schemes - post-compensation and pre-compensation, when DCF is placed at the beginning or at the end of line - has been investigated. We have performed a comprehensive analysis and we have found that optimal degree of compensation is approximately 85 % for post-compensation scheme and 90 % for pre-compensation scheme. Assuming optimistically the attenuation of G.652 fibre to be 0.22 dB/km, it follows from analysis that maximum transmitter-receiver distance is 270 km for post-compensation scheme and 230 km for pre-compensation scheme with BER<10^-12.

At the same time, we began with practical verification of simulations. We bought Cisco Catalyst 6503 with 10GE 1550 nm line cards with maximum distance of 40 km and we used field-tested Keopsys optical amplifiers. Cisco systems routers and switches are deployed in CESNET2 production network and therefore the research results can be utilized for partial upgrade to 10GE.

The results can be summarized as follows: for distances up to 100 km one can use boosters only without compensation of chromatic dispersion. When booster and preamplifier are used, it is possible to cover the distances up to 200 km, for these distances it is necessary to compensate the effect of chromatic dispersion. With the use of 3-W Keopsys Raman fibre laser we were able to cover a record-breaking NIL distance of 250 km. During these experiments, the best results were accomplished with the combination of both post and pre-compensation schemes.

It has to be kept in mind that transceivers and receivers of 10GE line cards have parameters according to standards, when high-quality DWDM lasers are used, it is possible to expect additional increase of maximum distances with NIL approach. In that case, it is possible to cover the distances among all major cities in the Czech Republic and the results are employable for most of the European countries. Further research plans were framed in application form for grant entitled "Optimization of data transmission at 10 Gbps over G.652 fibres without the deployment of in-line EDFAs with respect to maximum transmission distance", the grant was awarded by the Grant Agency of the Czech Republic. Duration of the project is 3 years, beginning in 2004.

Results of these practical experiments were presented at Terena conference in 2003 Optically Amplified Multigigabit Links in the CESNET2 Network. Another contribution was presented at ConTel 2003 conference in Zagreb. Both presentations were positively accepted and some of NRENs were interested in 10GE deployment with NIL approach.

Former results of simulations and experiments entitled Optical networking in CESNET2 gigabit network were accepted for publication in journal Annales of Telecommunications. Brand new theoretical and experimental results were summarized in paper Optimization of NRZ data transmission at 10 Gbps over G.652 without in-line EDFAs to be published in Fiber and Integrated Optics journal.

5.4.7   Gain Stabilization in All-Optical Gain-Clamped Lumped Raman Fibre Amplifier

In optical networks with WDM channel addition/removal, fibre amplifiers with fast gain stabilisation must be used to suppress transition effects as a result of changes in the number of transmitted channels. For these reasons, we started to investigate an application of all-optical gain-clamped lumped Raman fibre amplifiers. We have developed our own simulation software for numerical analysis of transition effects in RFA and theoretical results were verified experimentally. In experiments, DCF module was used as RFA and channel addition/removal was simulated by transmitting signals of two lasers, light of one of the lasers was square-wave modulated at 500 Hz, power fluctuations of the other laser caused by cross-gain modulation of the RFA were monitored at the output of the amplifier with a digital oscilloscope with and without all-optical feedback. With optical feedback applied, we achieved suppression of transition effects by 10 dB.

Theoretical and experimental results were summarized in the following papers:

• M. Karásek, J. Kanka, P. Honzátko, J. Radil: Channel Addition/Removal Response in All-Optical Gain-Clamped Lumped Raman Fiber Amplifier sent for publication to IEEE Photonics Technology Letters
• M. Karásek, J. Kanka, P. Honzátko, J. Radil: Protection of Surviving Channels in All-Optical Gain-Clamped Lumped Raman Fibre Amplifier: Modelling and Experimentation, sent for publication to Optics Communications
• M. Karásek, J. Kanka, P. Honzátko, J. Radil: All-optical gain-controlled lumped Raman fibre amplifier was accepted for oral presentation on Optical Network Design and Modelling conference, ONDM 2004, Ghent, Belgium

5.4.8   Experimental 10G WDM Transmission System

As another step we have decided to assemble and to test in lab environment experimental WDM transmission system designated for deployment with dark fibres. We primarily tested multiple NIL transmissions of Gigabit (GE) and 10 Gigabit (10GE) Ethernet by means of NIL method.

Signals were combined via conventional 1×N directional couplers and the same couplers are used to split signals at the end of fibre. Subsequently, tunable optical filters must be used (DWDM or CWDM multiplexers can not be used because routers line cards are "of grey wave length", i.e., they are not tuned to ITU grid). It means the overall line length is smaller due to higher insertion loss of couplers in comparison to DWDM multiplexers. Achieved results are very interesting. We were able to transmit 2×GE and 2×10GE over 200 km standard G.652 fibre with EDFA amplifiers and Raman laser. Measured bit error rate for 10GE channels was better than 10^-13.

In another experiment, two 10GE signals were successfully transmitted over 250 km without use of in-line EDFAs. In the experiment, standard directional couplers and optical filters were used to combine and split individual channels, 3 EDFAs, 3 DCF and transmission fibre was pumped by Raman laser.

These results are encouraging both for NREN operators and especially for experimental networks like CzechLight, which is now projected, because standard equipment from major vendors (Cisco Systems, Nortel Networks, Lucent Technologies) is not always suited for specific requirements of these networks. Another important factor can be the price of such experimental WDM system and possibility for quick reconfiguration according to the needs of administrators or even end users.

5.5   Dark Fibre International Connection of NRENs

We checked out leasing possibilities of dark fibres over border in connection with preparation of participation of CESNET Association in international projects GARDEN and GRANDE and for other international activities.

During the year 2003 we preliminary inquired the circuits to Slovakia, Poland, Germany and Austria from inland providers of fibres. At first we demanded lines from Prague to Bratislava, Poznań, Frankfurt a. M., Munich, Berlin and Vienna. Based on acquired knowledge we requested the possibilities of connection for university towns or NREN PoPs near border. As a reply, we obtained proposals of international connections Brno-Bratislava, Brno-Vienna, Plzeň-Munich, Plzeň-Nurnberg, Ústí nad Labem-Dresden and Ostrava-Bielsko Biala. The table shows rough overview of possibilities. We point out that the prices for real procurement would be different (probably lower) and that the connection to Poznań would probably be agreed with Polish NREN, which is the owner of fibres in Poland.

We have already used the experience from negotiations about leasing of fibres in the international projects, principally SERENATE and GN2. The expenses on optical transmission systems for a neighbouring border NREN PoPs are lower (for example 50 %) than connection of NREN centres (located usually in capitals). We called this method NoB (Near over Border). Overlaying European infrastructure, like GÉANT, would be able to have lower number of circuits (e.g. only circuits longer than 1000 km) for lower expenses and better transmission of high data volume for long distances. Real possibilities of using this method will appear during procurement for data lines and fibres for project GN2.

The first international fibre connection of NRENs Brno-Bratislava by Gigabit Ethernet was realised in April 2003 thanks to the initiative of our colleagues from SANET (Slovak Academic Network) and laying shorter first mile fibre line to CESNET PoP at Masaryk University in Brno. It was found out that the traffic on this line is busy¹ (more than 150 Mbps), despite of the connection between CESNET and SANET from Praha to Bratislava. The traffic was even increased later by using other applications, especially experimental streaming of television and radio broadcast from SANET.

5.5.1   Equipment for Planned Dark Fibre Line Praha-Frankfurt a. M.

In connection with the possibility of dark fibre leasing between Praha and Frankfurt a. M. terminated in GEANT PoP, we investigated the optimisation of 10G single channel transmission system. We took into account the possibility to lease G.652 as well as G.655 fibres. OptiSystem software by Optiwave was used for numerical simulations and analysis, the total length of the line was 665 km. Required BER was better than 10^-12.

In case of G.652 fibre, 9 EDFAs and 8 DCF modules for compensation of chromatic dispersion have to be deployed for both transmission directions. If G.655 is leased, the number of EDFAs is reduced to 7 and only one DCF module is required. This reduction of both active and passive elements along fibre is very significant from financial point of view, even if the price for leasing of G.655 is usually higher than for standard G.652 fibre. It is not easy to perform exact economical analysis because prices of fibre leasing, EDFAs and DCF modules are vendor and intention dependent. In agreement with available background for our case study, the leasing of dark fibre and deployment of our own equipment was profitable for 25 % in comparison with purchasing of 10 Gbps lambda from a Telco operator.

Another step will be simulations of DWDM transmission system for the same dark fibre line.

5.6   Microwave-Based First Mile Connection for NREN Data Circuits

The goal of the project is to analyze the suitability of new first-mile technologies concerning the needs of the CESNET2 gigabit network. Furthermore, the project aims to propose and assess new solutions based on new standards regarding high-speed microwave devices (IEEE 802.11a/g/h).

5.6.1   Testing the Equipment Needed for 802.11g Transmissions in the Czech Republic

In June, the IEEE agreed upon the final version of the 802.11g standard concerning the 54 Mbps transmissions inside the 2.4 GHz band. There is reverse compatibility between 802.11g-compliant devices and older 802.11b-compliant ones. Mutual communication may be carried out at 11 Mbps.

The increase in speed was made possible by substituting the original CCK (Complementary Key Coding) modulation method used with the 802.11b DSSS (Direct Sequence Spread Spectrum) by the OFDM (Orthogonal Frequency Division Multiplexing) method, which is being utilized by the 802.11a Standard (5 GHz) as well. But 802.11g and 802.11a devices are not mutually compatible.

All 802.11b-compliant devices use the DSSS method and provide for maximum theoretical transmission speed of 11 Mbps (in reality, the speed reaches approx. 5.5 Mbps). Some companies have implemented the PBCC (Packet Binary Convolutional Coding) modulation method in their products. PBCC may double the speed, however the receiver has to be more sensitive and the signal-to-noise ratio has to be higher. This proprietary technology is often referred to as 802.11b+.

When employing the OFDM modulation used by the 802.11g/a standard, the band is divided into many narrow channels. These channels are used to transmit data at a relatively slow speed providing for more robust transmission than in the case of PBCC. The total data flow equals to the sum of the flow at all the channels and may reach 54 Mbps.

The theoretical transmission speed of 802.11g is 54 Mbps and it should work at the same range as 802.11b. However, the speed decreases rapidly with growing distance, while in the case of 802.11b, the speed should remain constant even close to the limiting distance. Another advantage of 802.11g is a simple migration of 802.11b to higher speeds.

802.11b and 802.11g may coexist as they both utilize the 2.4 GHz band. Thanks to that, existing 802.11b adapters are able to communicate with 802.11g access points. Naturally, the communication will be carried out at only 11 Mbps and the access point has to be configured to allow 802.11b communication (by decreasing the maximum transmission speed). 802.11a networks cannot be gradually upgraded in the above mentioned manner, as they utilize 5 GHz transmission band.

802.11g devices use modern hardware capable of encrypting the data being transmitted with just a slight drop in transmission speed (a few percent). On the other hand, encrypting data being transmitted by a 802.11b device may slow down the communication by up to 30 %.

Many 802.11g devices are currently available at the market.

• ORiNOCO - AP-2000 Access Point, AP-600
  http://www.proxim.com/products/wifi/11bg/
• D-Link - AirPlus Xtreme G
  http://www.dlink.com/
• Buffalo Technology - AirStation G54 Broadband Router Access Point (AP)
  http://www.buffalotech.com/wireless/index.php
• Linksys - Wireless-G Access Point WAP54G
  http://www.linksys.com/products/
• and others ...

Manufacturers offer a broad scale of products ranging from PCMCIA cards and USB devices to access points combined with simple switches or firewalls.

A PCMCIA card costs approx. CZK 3,000, while the cost of access points varies from CZK 8,000 to CZK 15,000 and sometimes even to CZK 20,000. Cheaper access points are not usually equipped with monitoring tools and that is why choosing the best position of the antenna and finding a free channel may be somewhat difficult. Also, it is not usually possible to find out how fast the devices communicate.

We have performed several tests at the turn of September and October. We have tested an 802.11g Buffalo AirStation-G54 purchased by the University of West Bohemia for the purpose of connecting student dormitories. We have completed indoor tests at ranges of 1 to 30 meters as well as outdoor tests at ranges varying from 1 to 6 km.

Buffalo AirStation-G54 has been designed to be used mainly indoors. It supports both 802.11b and 802.11g and may work either as a multi-client access point or as a point-to-point bridge. It features an internal antenna used for indoor operation. For outdoor operation, it is possible to connect an external antenna (the connector is of the type used by ORiNOCO as well). Besides that, the access point is equipped with four Ethernet ports and may be used as a switch.

The device is configured by means of an embedded web server (and we do not consider it as very well-considered). It lacked the means to monitor signal intensity (signal/noise ratio) or the transmission speed used to communicate with the partner device. The device supports encryption and access lists.

Transmission speed tests have been carried out using two identical Buffalo AirStation-G54 access points working in the point-to-point mode. We tried to transfer files of different sizes, i.e., megabytes, tens or hundreds of megabytes (the size did not affect the speed) via HTTP and FTP. The access points were allowed to use 802.11g only and we tried several power output values ranging from 8 to 22 mW.

Indoor use, 1 m, internal antenna, 22 mW power output

The actual transmission speed maintained throughout the test was 21.6 Mbps. In our opinion, this is the maximum the device is capable of. After enabling data encryption, the transmission dropped slightly to 20.8 Mbps.

Indoor use, 30 m, internal antenna, 22 mW power output

With direct visibility, we managed to reach the transmission speed of 21.6 Mbps. However, every obstacle did cause a significant drop. Maintaining communication through eight walls is extremely difficult and the communication becomes unstable. To build a good-quality internal infrastructure, it would be necessary to use better internal antennae.

Outdoor use, 1 km, ext. antenna (17 dB gain), 8 to 22 mW power output

Noise generated by the city interferes with the transmission and it is difficult to find a free channel. Under the same conditions, the ORiNOCO 802.11b device communicates at 3-4 Mbps with data encryption disabled.
Buffalo can communicate at approx. 10 Mbps and encryption causes just a slight decrease to the speed. The transmission speed maintained the same rate when used to connect two computers as it did when set up to provide communication for virtually hundreds of computers found in the student dormitories.
During a short-term test at 22 mW of power output (this value exceeds limits set by the standards), the transmission speed alternates from 7 to 11 Mbps depending on the level of interference. At 8 mW (complying with the standards), the transmission speed alternates from 6 to 10 Mbps.

Outdoor use, 6 km, external antenna (17 dB gain)

No noise, all channels are free. The ORiNOCO 802.11b device maintains transmission speed of 5.5 Mbps (maximum speed achievable with this kind of equipment regardless of the distance). After enabling encryption, the speed drops down to 3.7 Mbps.
Buffalo communicates at 1 Mbps. At this range, it is possible to perceive a dramatic reduction of the transmission speed. After switching on the 802.11b mode, the speed increases to 4 Mbps regardless of the encryption setting.

The Buffalo AirStation-G54 rates among cheaper 802.11g/b access points - its price is approx. CZK 8,000. As well as in the case of 802.11b devices, the suitability of the device for an actual solution depends on distances and local conditions. Thanks to the technology, the device may communicate faster with encryption on (recommended) and mode set to 802.11b (which may be done, should the need occur). In a city generating a lot of noise, it may reach 10 Mbps at 1 km. We were not able to test the following situation but it is possible to assume that in a noiseless environment, it could reach communication speeds of 10 to 20 Mbps at 1 to 2 km.

It is possible to use a circulator to boost the signal without exceeding legal limits. The circulator is positioned between the wireless card and the antenna and separates signal emitted by the transmitter from that emitted by the receiver. Basically, this means replacing one antenna with two antennae. The power output of the transmitting antenna may be low (lower than the limits), while the gain of the other antenna may be relatively high (for example 24 dB).

When acquiring new devices for new wireless links, it is preferable to buy 802.11g devices, as the prices of 802.11g and 802.11b equipment are almost the same. Transmission speeds should be higher and in case it proves necessary, the device may be configured to work in the 802.11b mode. For primary connections, it is more suitable to use higher-class devices (such as ORiNOCO AP-2000, AP-600), as they feature better throughout configuration system and monitoring tools.

5.6.2   802.11a and 802.11h Standards and Devices in the Czech Republic

After a long time, the Czech Telecommunication Office has issued an information on The Operation of RLAN Wireless Devices in the 5 GHz band (dated July 2003). According to this document, operation of 802.11a is prohibited. On the other hand, the 2.4 GHz band is public (covered by a general license) and generally available 802.11b (11 Mbps) a 802.11g (54 Mbps) devices may be used freely (a fact that causes a significant overload inside this band). The 5 GHz band is reserved for devices capable of Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC). Contemporary 802.11a (54 Mbps) devices do not meet this requirement.

The situation is very similar in other European countries. However, in July 2003, the World Radiocommunication Conference WRC-03 proposed changes to the Radiocommunication Code valid since January 1st 2005. According to the new regulation, individual countries will be allowed to implement their own general licenses concerning the 5 GHz band. The Czech Telecommunication Office is expected to follow this ruling.

In October 2003, the Czech Telecommunication Office proposed a Provisional General Licence allowing the 5 GHz band to be used freely to build wireless networks. However, the DFS and TPC conditions are not met by 802.11a devices. They are met by the 802.11h standard but no 802.11h devices are available at the moment. Theoretically, it should be possible to make a purely-software upgrade from 802.11a to 802.11h. However, this can hardly be guaranteed for all 802.11a devices available at present.

In future, it is possible to expect a new standard (802.11n), which will provide for transmission speeds exceeding 100 Mbps.

In conclusion, it is not possible to recommend investments into any infrastructure based on 802.11a. At present, the 802.11g seems to be the most suitable technology for legal high-speed connections.

5.7   CzechLight and TransLight

Within the frame of international projects on lambda services, one Cisco ONS 15454 box was purchased at the beginning of 2003 and it was connected to international exchange point NetherLight in Amsterdam via 2.5 Gbps circuit. Cisco ONS 15454 became the core of prepared network called CzechLight.

When some initial problems were solved (the very first box of its kind in the Czech Republic), we started to test and verify gigabit connectivity (GE channels) to Amsterdam and Geneva. During the first few months, some problems were discovered and they were not resolved until help from TAC Cisco. At the present time, CzechLight is used for connection between Institute of Physics ASCR Mazanka and CERN, Geneva and other lambdas are being prepared for international IPv6 connectivity and for experiments between CESNET and DataTag (Geneva and Chicago).

It was turned out during year that biggest problem is mutual agreement of end users and sometimes the problem is the lack of both of free ports and/or bandwidth (especially abroad) for requirements of various experiments. This kind of problems is now beginning to be solved within the framework of other international projects, especially for networks not under single administration policy (bandwidth on demand in multidomain environments).

CzechLight is an experimental network and it is possible to use it for potentially disruptive experiments. It is completely independent of production network CESNET2, which can't be used for this kind of experiments. As a consequence, some parts of this network are down and can't be used at all. For example, 10GE long-haul tests were performed on international NetherLight line between Amsterdam and Geneva during the summer and connectivity to CERN was completely lost.

Nowadays, CzechLight is a part of international experimental network TransLight which associates experimental networks of Canada, the USA, the Netherlands, Great Britain and northern European countries. The aim of TransLight is to verify the possibility to transfer large amount of data among relatively small number of users on international scale. With the help of this approach it is possible to eliminate expensive IP routers and to deploy new and cheaper equipment like TDM (time division multiplexers) or all-optical switches.

Experimental status of these networks allows to perform experiments even on the lowest layers i.e. directly on optical layer. Combined together with good availability of dark fibres (even international ones today), it affords opportunity to expand CzechLight into other cities in form of an experimental WDM system and to take advantage of our knowledge of NIL long-haul solutions. It offers brand-new opportunities to experimental and research networks.

5.7.1   Experimental Line Praha-CERN for Elementary Particle Physics Research

The full GE capacity link between Prague and the European laboratory CERN in Geneva was established for the use of the Institute of Physics AS CR (FZU) at the Mazanka campus in Prague. The link was used for the large-scale computer simulations of the detectors for the LHC (Large Hadron Collider) experiments (planned startup in 2007). FZU collaborates on the two LHC experiments - ATLAS and ALICE. We have taken part in both experiments Data Challenges - mass detector simulations - with the help of local computing farm Golias. One simulation task lasts typically one day and several hundreds simulations tasks are submitted during one simulation campaign. The results of one task are several output data sets, one of them with size of 200 MB is copied to CERN. During the tests in 2003 some 2 TB of data were transferred to CERN.

The amount of simulation tasks and volume of data transfers will grow in 2004 as a result of improvement in automation of task submission and monitoring of the simulation tasks what is one of the results of the CERN LCG (LHC Computing Grid) project. In the same time, Institute of Physics AS CR runs large-scale detector simulations for the project D0 of the Fermi National Accelerator Laboratory (FNAL or Fermilab) in Batavia, Il. Here we pay our contribution to the detector maintenance and operations by the delivery of the computing services. Further increase of the link capacity over the CzechLight and NetherLight to StarLight is desirable (realization of the Fermilab connection to the StarLight is expected soon).

5.8   Programmable Equipment for Long-Haul Transmissions - Perspective and Possibilities

In the present time we have begun the work on modular system that includes different optical and electronic units. Our goal is to integrate electronic units (based on the COMBO system in particular) together with optical transceivers and optical amplifiers (preamplifiers, in-line amplifiers, boosters) in 19" chassis suitable for placing in professional racks.

Unified access via SNMP will be used for monitoring of all modules. This conception allows us relatively simple creation of complicated functional blocks for both research and development plans and tasks and for use in production environment.

One of the most interesting applications, which uses both programmable logical arrays and optical components, is the design of electro-optical switch for speeds from 1 Gbps to 10 Gbps. We'd like to begin work on this task at the beginning of 2004.

In the first phase, we will focus on research and development of optical amplifiers from standard components (optical EDFA and RFA modules, powers, industrial PC). From these components it will be possible to design and assembly optical amplifiers suited for specific requirements of experimental and research networks (for example CzechLight) and for considerably lower prices than one can expect for commercially available and comparable equipment.

5.8.1   Design of programmable gigabit repeater

The design of the gigabit repeater is based on the card COMBO-4SFP (CESNET Technical Report 12/2003). The COMBO-4SFP is equipped with four SFP cages, two XILINX VIRTEX II FPGA, two SRAM and 3 serial flash EEPROM for the necessary configuration information. One EEPROM is used to keep info about the board (type of VIRTEX's, ID number of the board, etc.), the other two others are used for configuration of SFP's.

The COMBO-4SFP has been developed in the frame of Liberouter project as interface card for the COMBO6 (PCI hardware accelerator). Both power supply and download of firmware for the COMBO-4SFP are supported by host PC computer through COMBO6.

The desired functionality of the gigabit repeater is not as complex as the necessary functionality needed in the Liberouter project. All functions can be provided on the COMBO-4SFP with support of low end processor, boot engine and power supply.

We have built the low cost card COMBO-BOOT (CESNET Technical Report 14/2003) as the inexpensive replacement of the COMBO6 and the host computer. The COMBO-BOOT has two power supplies (input 12-20 V), flash memory for the firmware of both FPGA's, RS 232 interface and Texas Instruments MCU. Free development tools (including C language) for the MCU are available.

The most important goal for the MCU is to download firmware into flash EEPROM (through RS232) and boot FPGA's after power up. The MCU could be also used for the configuration of firmware (either through RS 232 or on board switches) and allowed to add SNMP functionality for the monitoring and control of power supply and link quality.

We suppose to place repeater into 19" 1U chassis with one or two means of power supply (any combination of 220 V and 48 V).

On the COMBO-4SFP we use ser/des chip VSC7145 which is able to work with four speeds:

• 1.25Gb/s Gigabit Ethernet
• 2.5Gb/s Infiniband
• 1.062GB/s Fiber channel
• 2.12Gb/s OC48

The repeater will be able to work with all these speeds.

As the COMBO-4SFP can work with all standard SFP transceivers the gigabit repeater is also able to provide functionality of media converter and could also be extended with optical amplifiers.

The design of the 2-port 10GbE card (COMBO-2XFP) for the SCAMPI project is being designed now. When the development is finished, we will use this card for the design of 10GE repeater.

 

Footnotes:

1. see http://www.cesnet.cz/provoz/zatizeni/

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