A Carrier’s Perspective on Implementing New Data Protocols Over Legacy

Networks

NFOEC 2003

September 10, 2003

Ian M. White1, Claudio Lima1, Greg Wolfe2, James Pan1

1Sprint Advanced Technology Laboratories2Sprint Wireline Technology Development

iwhite@sprintlabs.com

2

Legacy Carriers and Next Generation SONET/SDH

• Can legacy carriers benefit from the increasing demand for data services, despite their architecture?–The answer is YES.– Next generation SONET/SDH will enable legacy carriers to cost-

effectively offer data services.

• Some technologies are already in place to use.– Standards work is complete, products are on the horizon.

• Other technologies are immature or missing.

• We describe how legacy carriers can use Next Generation SONET/SDH to deliver new data services.– Benefits, cost savings, new services;– Challenges, unmet requirements.

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Legacy SONET/SDH Architecture

•SONET rings are the transport foundation of the metro core network.•Some L2/L3 switching capability is available on metro switches.•Many legacy IXCs reach clients through leased access.

– DS1/DS3 access is the most common (lack of deployed access fiber).

OC192, ring or mesh.IP/MPLS/ATM/FR core

IXC metro core network

IP/MPLS/ATM/FR

ILEC CO

Co-locatedMetro switch

ILECMetro/access

ILECMetro/access

IXC access methods:leased DS-1/3,

OC-3/12, opt. Ethernet

OC48 rings.SONET cross-connects with L2/L3 switching capability.

CPE

CPE

4

Legacy Carriers Must Provide New Data Services

•Must provide new data services using a legacy SONET/SDH network.

•This will require an overlay of new functions:– Data over SONET/SDH, and data over PDH (DS1/3).– Transport pipe size optimization.– E-LAN support in the MAN and WAN.– More flexible bandwidth control.

IP/MPLS/ATM/FR

SANtransport

Internet

E-LINE/E-LAN

E-LINE/ E-LANacross the WAN

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Next Generation Data-Over-SONET/SDH Protocols

•A new suite of protocols has been developed to enable legacy carriers to provide data services with low investment.– Generic Framing Procedure (GFP):

Maps any data protocol into SONET/SDH. Transparent GFP (GFP-T) is optimized for Fiber Channel,

FICON, ESCON.

– Virtual Concatenation (VCat): Data can be mapped into any quantity of non-contiguous

tributaries.

– Link Capacity Adjustment Scheme (LCAS): Standardized command set to enable hitless VCat capacity

modifications.

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Advantages of GFP

• The literature has identified many advantages of GFP:– Simpler, more robust packet delineation than HDLC.– Handles header and payload bit errors.– Maps any data protocol onto SONET/SDH.

• However, there will likely be only one immediately noticeable advantage to carriers.– Transparent GFP (GFP-T) transports Fiber Channel, FICON, ESCON

over SONET/SDH. This will enable legacy carriers to transport SAN data across any

distance. This is likely to be a fruitful source of revenue because of the desire of

the financial industry for geographical separation between data centers and backup sites.

• In the future, the ability to map any protocol may also be tremendously beneficial to carriers.– The Universal Line Card.

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Advantages of VCat (1)

• VCat enables more efficient use of transport bandwidth.– Can result in a significant savings on line card costs.

Without VCat

OC-48

OC-48

OC-48

GigE

GigE

STS-48c

STS-48c

STS-3c

100MbE

OC-48

IXC Metro Core Ring

IXC MetroCross Connect

IXC MetroCross Connect

STS-1-21v

STS-1-2v

With VCat

GigE

GigE

100MbE

GigEGigE

100MbE100MbE100MbE

GigEGigE

100MbE100MbE100MbE

Ethernet Private Line transport in the metro core network.

IXC Metro Core Ring

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Advantages of VCat (2)

• Virtual concatenation can be used to efficiently size the transport pipe for aggregated Ethernet traffic.

• Similarly, VCat can be used to efficiently size the transport pipe for RPR.• With VCat, efficiency is better than 80%, and almost always better than 90%.

OC-48

IXC Metro Core Ring

IXC MetroCross Connect

STS-1-Nv

AggregatedEthernet

L2switch

Ethernet, TDM

services

Ethernet Virtual Private Linein the metro core network:

Transport Efficiency over SONET

0

20

40

60

80

100

120

0 500 1000 1500 2000 2500

Payload (Mb/s)

Eff

icie

ncy

(%

)

Without VCat

With VCat

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Low Order Virtual Concatenation

• LO VCat is NOT APPROPRIATE for the metro core and long-haul core network.

– To many circuits to manage (carrier operations teams and chip makers agree).

• However, LO VCat will be beneficial in the access area to transport Ethernet from multi-tenant units (MTU).

CPE10/100

EthernetOC-3

To metro core

VT1.5-Nv

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VCat Differential Path Routing•Can use differential path routing to create new level of service

protection.– Might be a long time before this fits into carriers’ operational models.– Probably only useful in the long-haul core network.

•Could be problematic if deployed without LCAS (or similar function).– Should quickly drop group members if their path is cut or severely errored.

•Differential delay compensation:– ITU standard (G.707) suggests a maximum of 512 ms.– In reality, anything over 100 ms is more than sufficient.– In fact, 32 ms is sufficient for most continental networks.

STS-1-2v

Diff. Delaycompensationmetro

WAN

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LCAS for Bandwidth Management and Protection

•Standardized method of bandwidth adjustment is necessary.– Bandwidth adjustment may occur across different metro areas with

different vendor equipment present.

•LCAS will be useful with VCat differential path routing if the data service is not protected with SONET or RPR.– If a path is lost or severely errored, the network management

system must quickly remove the affected VCat members from the group.

– Carriers may also use LCAS to add new members to restore the capacity.

STS-1-2v

Diff. Delaycompensation

Remove from groupafter failure

Re-add to group ifbandwidth is found

metroWAN

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Service Multiplexing with Data-over-SONET/SDH•New data services require service multiplexing:

– Aggregation of data being backhauled to the public Internet.– Virtual Ethernet Private Line aggregation.– E-LAN services.

•Only sites equipped with GFP/VCat can perform service multiplexing.– GFP/VCat must be terminated before data can enter a switch.

•Service multiplexing for metro area services is straight forward.– Metro switches are equipped with GFP/VCat and L2/L3 switching.

IP/MPLS/ATM/FR

Internet

E-LAN

E-LAN across the WAN

Servicemultiplexing

Servicemultiplexing

ServicemultiplexingIXC Metro

core network

IXCWAN

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Service Multiplexing Across the WAN •Service multiplexing across the WAN is less clear than the MAN.

– MPLS/ATM/IP will exist in the WAN, but GFP/VCat may not.– To avoid GFP/VCat deployment in the core, carriers must avoid using

GFP/VCat with service multiplexing in the core. Terminate GFP/VCat at the POP at the edge of the core. Ethernet Private Line is still okay – no need to terminate GFP/VCat.

– This is probably an acceptable situation for carriers. Most carriers currently have excess bandwidth in their core. Thus, limiting GFP/VCat to the metro may be acceptable.

IP/MPLS

IP/MPLS

TerminateGFP/VCat

TerminateGFP/VCat

TerminateGFP/VCat

IP/MPLS

metroWAN

metro

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Operations Management for Data Over SONET•End-to-end operations management functionality for data over

SONET is immature.•During GFP standard development, the expectation was to use

the GFP Client Management Frame (CMF) to carry Ops Mgmt data and commands.

•This approach may have limitations.– If a carriers wants to place centralized Ops Mgmt in the core,

GFP/VCat must be terminated (differential path routing constraint).– Dial-up line to edge equipment from centralized management point

may be costly because many legacy carriers use leased access.– Appears to be sufficient for Ops Mgmt of metro services.

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Operations Management for EPL in the WAN•Carrier may not want to use GFP CMF for Ops Mgmt of Ethernet

Private Line across the WAN.•There is a proposal* in ITU to use SONET Path Overhead (POH).

– Tester is placed in the core of the network to monitor/intercept Ops Mgmt.

– Avoids the need to terminate GFP/VCat in the core.– Avoids dial-up line access across leased access.– Also works for architecture where GFP mapping is leased from

wholesale provider.

•Still in the early stages of development and definition.

*ITU-T Draft G.smc, version 0.0.1, January 2003

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Data over PDH (DS1, DS3)•Legacy IXCs spend a lot of money on local access.

– But costs must be minimized to cost-effectively support data services.

•Lowest cost approach: use DS1/DS3 to carry data into the metro.– Use multiple DS1/DS3s bonded together to form the data pipe.– Some initial offerings are available, but in general the technology is

still under development.

•Open question: Can VCat technology be leveraged for inverse multiplexing data services across DS1/DS3?

•GFP over DS1/DS3 must be standardized.– The standard is currently in progress.

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Summary and Conclusions

•Legacy carriers will benefit from next generation data-over-SONET.– VCat will save line card costs in the metro core.

Potentially more than 50%, because of improvement in Gigabit Ethernet transport.

– GFP will enable standardized transport of SAN data.– GFP may eventually contribute to a universal line card.– LCAS may offer interesting service protection options.

•More technology is needed.– Definition of end-to-end operations management for data-

over-SONET.– Cost-effective transport of Ethernet over DS-1/DS-3.– Better understanding of how E-LAN functionality can be

supported across the WAN with/without GFP/VCat.