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Following a period of intense research activities with our main vendors and the definition of our mid-to-long term strategy, Colt has started a project to execute the integration of the long-haul DWDM L1, the Carrier Ethernet L2 and the IP L3 layers into a single platform. Our presentation at WDM & Next Generation Optical Networking 2012 examines in particular the reality of circuits versus packets at Colt as well as two hot cases in the industry: router by-pass and OTN switching versus MPLS switching.
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© 2012 Colt Telecom Group Limited. All rights reserved.
Packet optical integration plans for OTN and MPLS switching technologies
Network & IT Platform Strategy and Architecture
2
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
3
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
4
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
5
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
6
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
7
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
9
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
10
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
11
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
12
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
13
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)
14
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)
15
Router bypass and circuit versus MPLS switching
PEPOTN
MPLS
service VLAN
transport tunnel
service tunnel
What type of inter-PE connectivity on transit sites?
16
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)
17
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. [email protected]