SDH-Part IV (Next Generation)

1EETAC 3B

SDH IV: NG-SDH3B. BACHELOR IN TELEMATICS ENGINEERING

Cristina Cervell i [email protected]

Contents2

Functional Architecture: network elements and topology

SDH Basics

SDH Transport Services

Protection Mechanisms

Synchronization

Next Generation SDH

2SDH challenges

Fine granularity to accommodate all potential clients stream rates.

How to use bandwidth efficiently for both voice and data traffic.

New services and applications based on IP, mobile, multimedia, DVB,

SAN, Ethernet or VPN, demanding long haul transport.

SDH/SONET networks offer features for long-haul transport, that

include: Resiliency, Reliability, Scalability, Built-in protection and

Management.

The data packet transport (Ethernet, IP, DVB) was a challenge for

SDH.

This is because these services are connectionless, use statistical

multiplexing, and can be best-effort technologies.

This is the opposite of SDH which is predictable and based on time

division multiplexing (TDM).

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Next Generation SDH (NG-SDH)

The drive to SDH Next Generation development was:

The desire to find one simple encapsulation method that was capable of

accommodating any data packet protocols.

Secondly, the need to use bandwidth accurately.

Solution: A new adaptation protocol layer is required and a new

mapping mechanism for controlling the bandwidth use.

Next-generation SDH is the evolution and enhancement of existing SDH

networks.

It improves network efficiency and broadband service potential.

SDH Next Generation enables transporting data efficiently, without

needing to replace the installed equipment base.

The only change needed to update the network is to replace the edge

nodes.

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3Components of NG-SDH

VCAT: Virtual Concatenation (ITU-T G.707)

LCAS: Link Capacity Adjustment Scheme (ITU-T G.7042)

GFP: Generic Frame Procedure (ITU-T G.7041)

These functions are implemented on the new MSSP nodes which

are located at the edges of the network

They interact with the client data packets that are aggregated

over the SDH/SONET backplane that continues unchanged

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NG-SDH Architecture

Protocols Architecture

MSSP: Multi Service Switching Platform: include SDH multiplexing add-drop,

Ethernet ports, packets multiplexing and switching , WDM, switching TDM...

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G.7041

, G.7042G.707/783

4Next Generation SDH Network Elements7

Multiservice Provisioning Platform (MSPP)

A Multiservice Provisioning Platform (MSPP) is basically

the result of legacy ADM and TDM interfaces, to a type of

access node that includes a set of:

Legacy TDM interfaces

Data interfaces, such as Ethernet, GE, Fibre Channel or DVB

NG SDH functionalities such as GFP, VCAT and LCAS

Optical interfaces from STM-0 to STM-64

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5Multiservice Transport Platform (MSTP)

A Multiservice Transport Platform (MSTP) is basically a

MSPP with DWDM functions to drop selected wavelengths

at a site that will provide higher aggregated capacity to

multiplex and to transport client signals

MSTP allows to integrate SDH, TDM and data services, with

efficient WDM transport and wavelength switching

Typically, MSTPs are installed in the metro core network

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Multiservice Switching Platform (MSSP)

A Multiservice Switching Platform (MSSP) is the NG equivalent

cross-connect, performing efficient traffic grooming and

switching at STM-N levels but also at VC level.

MSSP should support more than just data service, namely true

data services multiplexing and switching.

Large MSPP systems, which have switching and grooming capacity

of at least 300 Gbps.

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6Current MSPP: unifying MSPP & MSTP

Example: the ONS 15454SDH provides TDM solutions with interfaces such

as E1, E3 and DS3, data solutions with 10/100/1000 Ethernet solutions with

STM1 to STM64 optical transport bit rates in both gray and DWDM (ITU

compatible) wavelengths. Capabilities:

Aggregation and transport of services from E1 to STM64

Flexible architecture with multirate (SFP-based) Ethernet and optical modules

Metro Ethernet Forum (MEF) Certified ELINE and ELAN

10 Gb Ethernet modules

Flexible networking support including rings, linear point-to point, linear add/drop, star, and

hybrid topologies

Restoration choices: SNCP, 2-fiber and 4-fiber MS SPR,

1+1 APS, unprotected span, and Ciscos Path Protected Mesh Networking (PPMN)

Compact footprint for deployment flexibility

(3 can fit in a 2000mm ETSI rack/cabinet).

Carrier Class Reliability

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Components of NG-SDH

GFP: Generic Frame Procedure (ITU-T G.7041)

VCAT: Virtual Concatenation (ITU-T G.707)

LCAS: Link Capacity Adjustment Scheme (ITU-T G.7042)

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7GFP (Generic Framing Procedure)

GFP (Generic Frame Procedure) G.7041

A standard mechanism of generic multiplexing and framing for transparent

transport of user data over SDH or OTN (G.709) networks.

Valid for framing any protocol.

Two modes of encapsulation (Framed and Transparent).

Frame oriented GFP-F.

Code oriented GFP-T (Optimized for low-latency, constant bit-rate applications)

(e.g., SAN or digital video delivery).

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GFP

GFP-F

GFP-F entirely maps one complete client frame into a single GFP frame.

Idle packets are not transmitted resulting in more efficient transport.

GFP-F is used where the client signal is framed or packetized by the client protocol e.g., Ethernet, PPP/IP and HDLC-like protocols.

To perform the encapsulation process it is necessary to receive the complete client packet, therefore this procedure increases the latency. It is optimized for bandwidth efficiency at the expense of latency.

Specific mechanisms are required to transport each type of protocol.

GFP-T

Transparent GFP (GFP-T) is a protocol-independent encapsulation method in which all client code words are decoded and mapped into GFP frames.

The frames are transmitted immediately without waiting for the entire client data packet to be received.

Low latency.

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815

GFP Frame15

GFP-F Mode16

9VCAT (Virtual Concatenation) G.707, G.783, Y.1322

Resolves the granularity problem of SDH adapting transmission speed to

user requirements by using virtual concatenation.

User data mapped to groups of virtual containers. Inverse multiplexing (G.805)

Optimizes the use of SDH network

Virtual Concatenation offers the user a granular bandwidth choice, optimizing

the use of network resources.

Better efficiency of the SDH network

Transparency in the SDH network

Individual VC are beared as traditional virtual containers.

Core nodes are transparent to VCAT.

End nodes must support VCAT functionalities.

Receiver node reassembles the user frame and must compensate the delay

differences of each path. Delay correction has a maximum limit of 512 ms.

Suitable for continental networks.

Terminology: VC-n-Xv with n = {4,3,12} and X according to provided

service

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Contiguous vs Virtual Concatenation18

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VCAT (Virtual Concatenation)

VCAT: Efficiency in data transmission

Service Rate Contiguous

Containers

Virtual Containers

Ethernet 10 Mbps VC-3 20,66% VC-12-5v 92%

Fast Ethernet 100 Mbps VC-4 66,77% VC-3-2v 100%

Gigabit Ethernet 1 Gbps VC-4-16c 41,73% VC-3-21v 98,43%

VC-4-7v 95,39%

ESCON 160 Mbps VC-4-4c 26,7% VC-3-4v 82,67%

Fibre Channel 850 Mbps VC-4-16c 35,47% VC-4-6v 94,6%

Fibre Channel 1.7 Gbps VC-4 16c 70,95% VC-4-12v 94,59%

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VCAT Efficiency

Example: Fast Ethernet (100 Mb/s)

Contiguous concatenation: VC-4

VC-4 (without POH): 260x9x8 bits, T=125 s 149.76Mb/s

Virtual concatenation: VC-3-2v

VC-3 (without POH): 84x9x8 bits, T=125 s 48.384 Mb/s

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Data Transport

Different containers of the same VCG (Virtual Container Group)

are independently transmitted

Frames arrive out of phase at the sink due to different paths.

Differential delay compensation required at sink.

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Differential delay is caused by:

geographically large ring with VC-ns from the same VC-n-Xv

routed around the ring in different directions, delay is mainly due

to fiber propagation (~5 s/km)

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Y VC-ns

(Y

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Differential delay is caused by:

networks with diversely routed path protected VC-ns, delay is

mainly due to fiber propagation (~5 s/km)

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End to end traffic: VC-n-Xv

Y VC-nson working path

(X-Y) VC-nson Protection path

Transportnetwork

Protectionpath

Working path

LCAS (Link Capacity Adjustment Scheme)

G.7042. Provides soft protection and a mechanism for load

sharing. Is an extension of virtual concatenation.

Designed to manage the bandwidth allocation of a VCAT path.

LCAS can add and remove members of a VCG that control a VCAT

channel. LCAS cannot adapt the size of the VCAT channel according

to the traffic pattern.

Dynamic bandwidth

Allows bandwidth changes during the service.

BW can be managed adding or dropping VC of VCG.

Protection and failure tolerance

Increases availability of VC from failures or changes.

Automatically decreases link capacity if a VC path has a failure,

increasing when repaired.

Protection mechanism applies efficiently to packet transmission.

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LCAS (Link Capacity Adjustment Scheme)25

Source to Sink messages:

Multi-Frame Indicator (MFI) keeps the multiframe

sequence.

Sequence Indicator (SQ) indicates members sequence to

reassemble correctly the client signal that was split and

sent through several paths.

Control (CTRL) protocol messages which can be fixed,

add, norm, eos, idle, and dnu.

Group Identification (GID) is a constant value for all

members of a VCG.

Sink to Source include:

Member Status (MST), which indicates to source each

member status: fail or OK.

Re-Sequence Acknowledge (RS-Ack) is an ack of

renumbering after a new eos member

LCAS Applications

VCAT bandwidth allocation. LCAS enables the resizing of the VCAT pipe

in use when it receives an order from the NMS to increase or decrease the

size.

Network Resilience. In the case of a partial failure of one path, LCAS

reconfigures the connection using the members still up and able to continue

carrying traffic.

Asymmetric Configurations. LCAS is a unidirectional protocol allowing the

provision of asymmetric bandwidth between two MSSP nodes to configure

asymmetric links

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Services over GFP27

NG SDH Application: EoSDH (EoS)

The Keys to Ethernet Services Success

Rapid return on investment. Recoup CAPEX in under a year, model deployed

leverages legacy transport infrastructure.

Legacy compatibility and interoperability. Leverage the installed base of

transport and packet services infrastructure

Bandwidth efficiency. Ethernet must be transported as efficiently as possible,

with options for statistical multiplexing and efficient mapping to SDH/SONET

transport bandwidth.

Resiliency. Solution with strict protection and restoration capabilities equivalent

to services carried over a SDH/SONET infrastructure.

Comparable profiles to existing Layer 2 services. Customers have expectations

of service quality, service guarantees, security and service flexibility that must

be matched by Ethernet.

End-to-end management, monitoring and provisioning.

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Ethernet Service provided with LCAS/VCAT29

Ethernet service

The MEF (Metro Ethernet Forum) has defined the following

three basic Ethernet connectivity services within and between

metro areas:

E-Line (point-to-point)

E-LAN (multipoint-to-multipoint)

E-Tree (rooted-multipoint)

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E-Line

Ethernet Private Line (EPL): Provides dedicated bandwidth and

guaranteed throughput across a point-to-point connection. EPL is analogous

to a "circuit-like service such as an E1 service which is permanently

reserved and dedicated for an enterprise customer.

Ethernet Virtual Private Line services (EVPL): Dedicated point-to-point

VPN service connecting two customer sites over a shared bandwidth

supporting statistical multiplexing and oversubscription. It takes advantage

of Ethernet's lower-cost bandwidth to share resources amongst multiple

customers. The EVPL service is aware of service attributes and can offer

different QoS (delay, jitter, and frame loss), thus introducing a service

differentiation offering to customers.

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EPL EVPL

E-LAN

Ethernet Private LAN (EPLAN): An E-LAN service that provides

multipoint connectivity over dedicated bandwidth. This service

provides high-speed LAN interconnection amongst multiple customer

sites which appear to be linked by a LAN segment.

Ethernet Virtual Private LAN (EVPLAN): Provides a packet-based

service that delivers secure any-to-any connectivity across a shared

infrastructure supporting statistical multiplexing and oversubscription.

EVPLAN service supports multipoint-to-multipoint connectivity and

point-to-multipoint service.

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EPLAN and EVPLAN 3 connectivity examples33

Mesh connectivityTraffic hauled to centralized

switching point(s)

Switching at network edge (hub and spoke)

Ethernet service

The following metro Ethernet service delivery technologies can

be used:

Ethernet over SONET/SDH (EoS)

Ethernet Leased Line over SONET/SDH (EoS LL)

Switched Ethernet (Layer 2) over SONET/SDH (SW EoS)

Ethernet over DWDM (EoWDM)

Ethernet over Fiber (EoF)/Ethernet transport

Resilient Packet Rings (RPR)

Provider Backbone Transport (PBT)/PBB-TE

Ethernet over MPLS (EoMPLS)/T-MPLS

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Ethernet Leased Line over SONET/SDH

Typically used for Ethernet private line applications, Ethernet over

SONET/SDH.

EPL is a point-to-point service with a native Ethernet interface. EPL was

developed as a packet data transport solution which would allow the

use of the existing deployed SONET/SDH infrastructure.

Benefits of Ethernet over SONET/SDH

Highest possible security available; using separate VC for service

delivery

High availability; relay on SDH protection and enhanced by LCAS

functionality

End-to-end simple provisioning

High granularity; guaranteed service with a minimum of 2M bandwidth

steps

Relatively inexpensive cost as add-on to existing optical networks with

spare capacity in MSPP products

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Ethernet Leased Line over SONET/SDH

Ethernet Private Line (EPL)

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Layered Architecture for EPL services37

Service Port

Switched Ethernet (Layer 2) over SONET/SDH

Switched Ethernet over SDH shares an SDH connection amongst several

customers. To ensure service quality, each customer is assigned a VLAN tag

and specific QoS through:

A committed information rate (CIR) for guaranteed bandwidth.

A peak information rate (PIR) for traffic bursts.

Traffic metering, shaping, and scheduling.

Main characteristics of Ethernet virtual services

Enables customer separation based on a logical frame identifier (VLAN tags),

and also supports Double Tagging/Q-in-Q (C-Tag and S-Tag). Double tagging

improves the scalability of the limited range of possible VLAN instances (4096).

Provides connectivity with a frame infrastructure that is shared between a

number of customers.

Performs bandwidth allocation per customer, not as a fixed allocation.

Supports statistical multiplexing of the bandwidth amongst customers.

Uses Spanning Tree Protocols to prevent loops (xSTP).

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Switched Ethernet (Layer 2) over SONET/SDH

The most basic Ethernet virtual service multiplexes multiple customer flows

within a designated infrastructure. Such Ethernet services can be referred to

as Ethernet Virtual Private Line (EVPL) or Ethernet Virtual LAN services

(EVPLAN).

Benefits of Switched Ethernet over SDH

Allows leveraging the existing network infrastructure while keeping capital

investment at a minimum and produces additional revenue-generating

opportunities.

Secures service by separate customer traffic using VLAN.

QoS support for real-time and premium services using basic CoS service

differentiation.

Resilience using xSTP restoration mechanism which provides greater than 50

msec, or relay on SDH protection and LCAS functionality in less than 50 msec.

Efficient bandwidth usage with its statistical multiplexing benefits allowing one

port to connect to multiple (up to 4,096) customer ports.

Cost-effective Provider Bridge Ethernet over SDH/SONET in point-to-point, ring,

hub-and-spoke, and mesh configurations.

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Switched Ethernet (Layer 2) over SONET/SDH40

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Recomendations ITU over SDH

G.810 Definitions and Terminology for Synchronisation

Networks.

G.811 Timing Characteristics of Primary Reference Clocks.

G.812 Timing Requeriments of Slave Clocks Suitable for Use as

Node Clocks in Synchronization Networks.

G.813 Timing Characteristics of SHD Equipment Slave Clocks.

G.825 The control of Jitter and Wander within Digital

Networks which are based on the Synchronous Digital

Hierarchy.

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Recomendations ITU over SDH

G.832 Transport of SDH Elements on PDH Networks: Frame

and Multiplexing Structures. Interoperability PDH-SDH.

G.841 Types and Characteristics of SDH Network Protection

Architectures y G.842 Interworking of SDH Network

Protection Architectures.

G.703 Physical/Electrical Characteristics of Hierarchical Digital

Interfaces.

G. 957 Optical Interfaces Of Equipments and Systems Relating

to the SDH.

G.958 Digital Line Systems Based on the SDH for Use on

Optical Fibre Cables.

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Bibliography

Gilbert Held, High Speed Digital Transmission Networking, Ed. John Wiley &Sons, 1999.

W. J. Goralski, Sonet, Ed. MacGraw-Hill, 1997.

U. Black, S. Waters, SONET & T1: Architectures for Digital Transport Networks, Ed. Prentice Hall, 1997.

G. Dobrowski, Donald W. Grise, ATM and Sonet Basics, APDG Publising, 2001.

D. Minoli, P. Johnson, E. Minoli, SONET-Based Metro Area Networks. E. MacGraw-Hill, 2002.

W. Goralski, SONET/SDH Third Edition. Ed. McGraw-Hill, 2002.

J. Philippe Vasseur, Mario Pickavet, Piet Demeester. Network Recovery : Protection and Restoration of Optical, SONET-SDH, IP, and MPLS. The Morgan Kaufmann Series in Networking. 2004.

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Additional slides44

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Protocol using byte H4

2ms

125s


Protocol using byte K4

SDH-Part IV (Next Generation)

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