© 2012 Colt Telecom Group Limited. All rights reserved.

Packet optical integration plans for OTN and MPLS switching technologies

Network & IT Platform Strategy and Architecture

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Contents

1 Three separate networks today

2 Benefits to integrate L1 & L2 & L3 onto one network

3 Review of integration plans and packet optical

5 Router by-pass and OTN versus MPLS switching

4 Circuits and OTN as the serving layer

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A network of depth and breadth

• High capacity long distance network - 35,000km

• Connecting 21 countries, 39 metro networks and >100 cities

• 19 (+1) data centres and 18,000 connected buildings

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Network layer integration – Historical situation

NB: Colt managed CPE (not customer’s)

L2 packet core

L3 packet core

L3 service

L3 CPE

IP services over Ethernet access (metro)

Ethernet services (metro & inter-metro)

L2 access &aggregation

L3 PE

L2 PEL2 service

L2 CPE

L2 CPE

L2 serviceIP NNI

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Benefits associated with network integration

Improved service unit costs (CAPEX/OPEX reduction, statistical multiplexing), better delivery lead time and TTR, L2 & L3 service blending (Integrated Routing & Bridging on PE)

Statistical multiplexing gain in the core

Reduced CAPEX (less devices per service, “pay as you grow” core) and OPEX (simplified delivery & assurance)

Operations, architecture, service nodes (PEs)Simplification

Technical

Product

Cost

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Network layer integration – L2/L3 CPE

L2 packet core

L3 packet core

L2 access &aggregation

L3 PE

L2 PEL2 service

L2 CPE

L2 CPE

L2 serviceIP NNI

L3 service

L3 features moving to the PE layer

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Network layer integration – L2/L3 edge

L2 packet core

L3 packet core

L2 access &aggregation

L2 service

L3 service

L2 service

L2 CPE

L2 CPE

L2/L3 PE

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Network layer integration – L2/L3 packet optical core

L2 access &aggregation

L2 service

L3 service

L2 service

L2 CPE

L2 CPE

L2/L3 packet optical core

L2/L3 PE

L3 featuresL3 features moving to the

core layer / cloud

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Vision on the best packet optical platform

• Multi-layer switching platform– WDM (colour-less, contention-less, etc.)

– OTN

– Packet

• OTN switching– Fill-in the high speed waves

• Packet switching– MPLS switching (LSR)

– No LER (VPN, VPLS, GRE, MC), no BGP

– CP protocols (IS-IS, OSPF, TE, LDP, RSVP)

L2/L3 packet optical core

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Network layer integration – Design thoughts

Network design considerations

•L2 and L3 services integrated on the same physical infrastructure but kept logically separated through the use of dedicated VLANs

– Service QoS characteristics uncompromised thanks to no queue sharing (8xL2 queues + 8xL3 queues)

•Key protocols for L2 and L3 services

•No mandatory requirement of MPLS-TP for L2 services– To start with MPLS properly tuned seen good for the job (OAM included)

– … but over time MPLS-TP might be useful for service assurance activities

Functions L2 services L3 services

IGP OSPF IS-IS

Path computation NMS/OSS based IGP (core)

Topology discovery OSPF-TE (booked bandwidth) IGP

Path creation ERO + RSVP-TE IGP + LDP

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The reality of circuits versus packets at Colt

• Demand for SDH services (2.5 and 10Gbps) still exists– No foreseeable time for end of sale (not within the next 2 years)

– But largely outnumbered by Ethernet services (1 and 10Gbps)

• No demand for OTN services (wholesales) exists– And no early signs this is going to change

– But OTN switching capability (as an internal network feature) remains attractive

• High speed Ethernet services (1 and 10Gbps point-to-point) are provisioned over the optical transport layer– But 1 and sub-10Gbps are being moved to the MPLS packet transport layer as scale of

this layer increases

• Sub-1Gbps Ethernet, IP and VoIP services are provisioned over MPLS– Integrated packet optical core to become more prominent in the future

Proportion of circuits decreasing over time

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Circuits supported by different flavours of OTN

• OTN framing– Proven track record with G.709 digital wrapper with FEC

– Even used in packet platforms (IP over WDM with coloured optics)

• OTN multiplexing– Must have LO ODU to efficiently fill-in waves in point to point topology

1G circuits

10G wave

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Circuits supported by different flavours of OTN

• OTN framing– Proven track record with G.709 digital wrapper with FEC

– Even used in packet platforms (IP over WDM with coloured optics)

• OTN multiplexing– Must have LO ODU to efficiently fill-in waves in point to point topology

• OTN switching– Useful to more efficiently use waves in transit situations (bus topology)

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Circuits supported by different flavours of OTN

• OTN framing– Proven track record with G.709 digital wrapper with FEC

– Even used in packet platforms (IP over WDM with coloured optics)

• OTN multiplexing– Must have LO ODU to efficiently fill-in waves in point to point topology

• OTN switching– Useful to more efficiently use waves in transit situations (bus topology)

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Router bypass and circuit versus MPLS switching

PEPOTN

MPLS

service VLAN

transport tunnel

service tunnel

What type of inter-PE connectivity on transit sites?

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Router bypass and circuit versus MPLS switching

Router bypass not seen too hot for Colt… if technically achievable

What type of inter-PE connectivity on transit sites?

•No router bypass but MPLS switching on transit nodes– Simplified architecture hence simplified operations (less tunnels, one case policy)

– Only marginal extra costs as co-located OTN and LSR functions

– Statistical multiplexing benefit (assuming minimum traffic variability)

– Additional latency reasonably negligible

– Potential scale concerns for large tier-1

•Router bypass i.e. circuit switching on transit nodes– Challenge to map inner LSP transport tunnel to separate circuit (burn dedicated ports

on P and OTN as an expensive mitigation step)

– Circuit bandwidth tax (more controllable if using low granularity ODUFlex)

– Better latency in general (unless store & forward mapping scheme used)

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Summary

• Packet transport layer likely to become the pivotal transport layer– Services run packets and use only 1/15th of their contracted bandwidth

• Great stories in optics to bring in 100G+, SD-FEC, flexible grid, etc.– Unclear rationale to massively scale the optical and OTN layers if the network

would run no actual traffic

• Different implementation scenarios for packet optical– LSR switching on optical core (with packet CP) or, in a later timescale,

Software Defined Networks controller (ONF or IETF definition)

MPLS switching: yes

OTN switching (infra): yes today

Decision factors: demand, scale, pricing

© 2012 Colt Telecom Group Limited. All rights reserved.

Thank you. Questions?valery.augais@colt.netwww.colt.net