valentino cavalli workshop, bad nauheim, 16-17 june 2003 1 ways and means of seeing the light...

Workshop, Bad Nauheim, 16-17 June 20031

Valentino Cavalli <[email protected]>

Ways and means of seeing the light

Technical opportunities and problems of optical networking

Valentino CavalliTERENA



Background

• Study on developments of equipment for optical transmission, switching and routing

• Technical sessions at:– Initial Workshop– Operator’s Workshop– NREN’s Workshop

• TF-NGN/ASTON group:– Direct involvement in meetings with vendors,

Discussion at TF-NGN meetings, white paper of lower layer research areas



Index

• Current networking environment, emerging factors and challenges for NRENs

• Technology facts and developments concerning fibres, transmission equipment, switches and routers

• Consequences in terms of network management and network architecture

• Conclusions



Current Environment

• Shared IP, basically best-effort and ubiquitous any-to-any service

• Networks currently over-provisioned (with exceptions in some countries and generally at the campus level)

• Guaranteed performance and traffic engineering mostly at the IP routing layer

• Simple and transparent model, easy management



Emerging factors

• Access to fibre much easier than in the past: universities and NRENs exploring a DIY approach towards network infrastructure

• Developments of WDM equipment, opto-electronics and all-optical devices.

• Increased availability of bandwidth but also increased need

• Changes in traffic patterns• Need for high-bandwidth p2p connectivity between a

limited number of locations to support large data flows• Dynamic, on-demand bandwidth management, requiring

network-aware middleware



• DIY approach towards network infrastructure, but to what extent? Campus, National, International?

• Depends on reach, but is actually happening at Campus and National level.

• More complex internationally, not only because of distance, but also need to provide services end-to-end across multiple administration domains

• New expertise also required• Change of traditional customer-supplier relationship with

carriers, more collaboration is possible and needed

What are NRENs facing?



• Physical transmission layer (Optical fibre)

• WDM equipment:– End-points, add-drop multiplexers,

regenerators, amplifiers

• Switches• Routers

Technology



Optical transmission

• Wide availability of fibre but limited to certain locations (even within a country)

• Need for amplification, signal regeneration, dispersion compensation: limitations of existing fibre plants

• Different access options:– leased connectivity, managed fibre, long-term lease,

fibre ownership• Cost effectiveness: Dark fibre vs managed wavelength• Issue: Operation might require install and maintain

equipment at remote locations for NRENs



• transmission technology allowing today (DWDM) up to 40 Gbit/s on a single wavelength, up to 160-190 wavelength per fibre, up to several Tbit/s per fibre

• Analogue technology, standardisation limited to ITU Wavelength Grid, limited interoperability

• Lot of dependency on fiber type and quality, dispersion, etc., needs to be tailored to each specific situations

WDM equipment



Capacity and reach

• Transmission capacity at 40Gbit/s per wavelength (channel) available, multiples of 40Gbit/s being tested– Costs of the electronics impact on interfaces, router

line-cards, etc.– Market demand not clear yet

• Depending on fibre type current 2.5-10Gbit/s systems require regeneration after 4-5 amplification spans (spans varying between 80-120km) so 400-600km, new generation ULH systems can reach up to 4000km

• Experiences with NIL up to 230km (GE and 2.5Gbit/s), 180km at 10GE



Optical switching

• Wavelength termination and signal regeneration require OEO conversion, transponders are very expensive, but OOO Switching equipment terminates only local traffic and does not impact on express traffic

• OOO switches are signal-transparent, lower unit cost, footprint and lower operational costs

• Generally support a variety of framing interfaces SONET/SDH, GE, 2.5, 10 GE, G.709, GFP

• Electrical technology still needed at user interface for multiplexing and bandwidth grooming



Routing

• Wide range of functionality supported: IPv6, multicast, QoS, MPLS

• G-MPLS already available, but little interoperability

• Support for multiple 10Gbit/s, 40Gbit/s bit-rate interfaces is available, but line-rate interfaces exploiting the full capacity of transmission links are not there yet– Cost of ASICs – mass production

• Driving introduction of 40Gbit/s



Management

• A mix of networking elements requiring a unified control plane and sophisticated management systems to seamlessly manage network and transport layer

• several signalling protocols being standardised by IETF and ITU-T

• Inter-operability, and multi-domain management still represent a challenge– More cooperation among network operators

to provide e2e services across domains



Network architecture

• Shared IP model,higher meshing? Gigabit core routers increasingly expensive at higher speed

• Circuit switching addressing “heavy” user needs?• Over-provisioning is no longer a cost effective solution• Simple extension of shared IP model does not scale,

need to explore hybrid network architecture solutions– Routers and switches can be combined in providing a

flexible network architecture– Limited cost saving but more efficient way of serving

users– Engineering traffic not only at layer 3 but also at

layers 2 and 1



Conclusions

• Simple extension of shared IP model does not scale, need to explore hybrid solutions– Circuit/lambda switching coexisting with IP routing

• 40Gps/s will happen soon • Exploitation of dark fibre depend on economics and reach

– At less than 250km NIL solutions seem viable• Management functions crossing multiple domains are being

developed, but:– more work needed in standardisation of signalling

protocols– Need to address complexity of providing end-to-end

services in multi-domain (and multi-vendor) environment

valentino cavalli workshop, bad nauheim, 16-17 june 2003 1 ways and means of seeing the light...

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