Cisco SDH Presentation

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Chapter 1

Network Architecture 2001, Cisco Systems, Inc.

ObjectivesUpon completion of this chapter, you will be able to perform the following tasks: Identify the main terms used to describe network components Describe the link structure and network elements Describe the interface options and interface layers

2001, Cisco Systems, Inc.

Network Architecture-2

Agenda1.1 - Link Structure and Line Interfaces 1.2 - Network Elements Summary, Information Resources

2001, Cisco Systems, Inc.

Network Architecture-3

Section 1.1

Link Structure and Line Interfaces 2001, Cisco Systems, Inc.

ObjectivesUpon completion of this section, you will be able to perform the following tasks: Describe the functionality and interaction of the interface layers Define the three overhead layers Describe the topology concepts related to the overhead layers Describe the main features of electrical and optical interfaces

2001, Cisco Systems, Inc.

Network Architecture-5

Overhead Layer Conceptspath multiplex section regenerator section PTE path terminationservice (E1, E4..) mapping demapping

multiplex section regen. section REG regen. section termination regenerator section PTE path termination

regen. section REG ADM or DCS

regen. section termination

multipl. section termination

PTE = path terminating element MUX = terminal multiplexer REG = regenerator ADM = add/drop multiplexer DCS = digital cross-connect system

service (E1, E4..) mapping demappingNetwork Architecture-6

2001, Cisco Systems, Inc.

Regenerator Section Regeneration section layer is the lowest level of link components in a SDH network Deals with the transport of an STM-N frame across the physical medium Point-to-point connection between two regeneration section termination points with direct optical or electrical domain connectivity Terminated by Regenerator Section Terminating Equipment (RSTE) The Regeneration section is mainly designed to overcome physical limitations of the transport technology 2001, Cisco Systems, Inc. Network Architecture-7

Multiplex Section One or more consecutive regenerator sections might compose a multiplex section Main element to build different topologies (e.g. ring) Deals with the transport of path layer payloads across the physical medium Multiplex section is a point-to-point logical link that connects to ADM, MUX, or DCS devices These devices might not include a path termination Overhead is interpreted and modified by Multiplex Section Terminating Equipment (MSTE) Multiplex section (MS) overhead is accessed only after the section overhead has been first terminated 2001, Cisco Systems, Inc. Network Architecture-8

Path One or more connected multiplex sections may provide a transport service for a path Multiplex section may carry multiple paths by multiplexing Deals with the transport of various payloads between SDH terminal multiplexing equipment Path layer maps payloads into the format required by the MS Layer Communicates end-to-end via the Path Overhead (POH) POH is terminated and modified by Path Terminating Equipment (PTE) Regenerator and multiplex section overhead must be terminated to access the overhead 2001, Cisco Systems, Inc. Network Architecture-9

HO and LO Paths In SDH the PDH payload multiplexing is done at 2 different layers High-order (HO) path carries E3/E4 or similar payloads Organized into administrative units (AU) including higher order tributaries Low-order (LO) path carries E1/E2 or similar payloads Organized into tributary units (TU) including lower order tributaries

2001, Cisco Systems, Inc.

Network Architecture-10

Topology Concepts SDH topologies are designed for providing a flexible and reliable transport for required paths Main issues: Capacity planning, bandwidth provisioning Redundancy, automatic fail-over Delay and jitter control Typical topology concepts: Point-to-point links (with protection) and DCS/MUX Arbitrary complex topology may be built Interconnected protected rings with ADM/DCS Minimum resource usage (physical media) for avoiding single point of failures 2001, Cisco Systems, Inc. Network Architecture-11

Physical Layer - I.Services (E1, E2, E3, E4, Video, etc.)Map Payload and Path OH into VC

LayersPath

Payload and Path Overhead

Map VC and MS OH into internal signal Map internal signal and RS OH into STM-N signal

VC and MS Overhead STM-N Signal Light Pulse

Multiplex Section Regen. Section

Regen. Section

Optical Conversion

Physical

PhotonicTerminalNetwork Architecture-12

Terminal 2001, Cisco Systems, Inc.

Regenerator

Physical Layer - II. Line coding applied: CMI for electrical interfaces Guarantees transmit-receive clock synchronization Binary NRZ for optical interfaces May change for very high speeds (STM-256 or higher) into RZ solitons Does not guarantee enough 1-0 or 0-1 changes, and thus clock transmit-receive synchronization Depends on the frame content Scrambling is needed for a guarantee 2001, Cisco Systems, Inc. Network Architecture-13

Electrical Interfaces Defined to be as compatible as possible with existing PDH physical interfaces Same hardware should be used For intra-office applications only Maximum 150 m 75 Ohm coax for STM-1 155.520 Mbit/s, CMI line coding

2001, Cisco Systems, Inc.

Network Architecture-14

Optical Interfaces Intra-office (application code: I-) LED or MLM laser at 1310 nm or 1550 nm Up to 2 km, max. loss 7-12 dB Inter-office, short-haul (application code: S-) Low power SLM or MLM laser at 1310 nm or 1550 nm Up to 15 km, max. loss 12 dB Inter-office, long-haul (application code: L-) High power SLM or MLM laser at 1310 nm or 1550 nm (zero-dispersion or dispersion-shifted fiber) Up to 40-60 km, loss: 10-28 dB up to STM-1, 10-24 dB up to STM-16 2001, Cisco Systems, Inc. Network Architecture-15

Summary Describe the functionality and interaction of the interface layers Define the three overhead layers Describe the topology concepts related to the overhead layers Describe the main features of electrical and optical interfaces

2001, Cisco Systems, Inc.

Network Architecture-16

Review Questions How many layers are used to build up a SDH network? What is the purpose of the Multiplex Section layer? What is the purpose of the HO Path overhead and the LO Path overhead ? Why do electrical and optical interfaces have different line coding? Is there a Regenerator Section termination in a Terminal Multiplexer? Is a usual add-drop multiplexer also a Path terminating equipment? 2001, Cisco Systems, Inc. Network Architecture-17

Section 1.2

Network Elements 2001, Cisco Systems, Inc.

ObjectivesUpon completion of this section, you will be able to perform the following tasks: Identify main network concepts Describe the functions of typical network elements

2001, Cisco Systems, Inc.

Network Architecture-19

Network Concepts Networks should be designed by decomposition Service needs into layers Logical connectivity needs into subnetworks Devices might be categorized by functionality and role in the network layers and topology Multiple set of functionality may be integrated into a single device if it is economically feasible

2001, Cisco Systems, Inc.

Network Architecture-20

Terminal Multiplexer Terminal multiplexer is at the edge of the SDH network Provides connectivity to the PDH network devices and certain end-user equipment It includes a regenerator section, multiplex section, and path termination in one link

2001, Cisco Systems, Inc.

Network Architecture-21

Regenerator A regenerator simply extends the possible distance and quality of a line by decomposing it into multiple sections Replaces regenerator section overhead Multiplex section and path overhead is not altered

2001, Cisco Systems, Inc.

Network Architecture-22

Add-drop Multiplexer - I. Add/drop multiplexer (ADM) Main element for configuring paths on top of line topologies (point-to-point or ring) Multiplexed channels may be dropped and added Special drop and repeat mode for broadcast and survivability An ADM has at least 3 logical ports: 2 core and 1 or more add-drop Ports have different roles No switching between the core ports Switching only between the add-drop and the core ports 2001, Cisco Systems, Inc. Network Architecture-23

Add-drop Multiplexer - II. ADM always includes regenerator and multiplex section termination. However paths might not be terminated, but only switched from one multiplex sections channel to another multiplex sections channel ADM may be integrated with terminal multiplexer functionality for direct interfacing to non-SDH network elements ADM always processes and replaces the multiplex section overhead ADM may not change the path overhead (POH) POH is changed only if terminal multiplexer function is included 2001, Cisco Systems, Inc. Network Architecture-24

SDH Cross-connect ADM concept is extended to have many similar capacity ports with any-to-any channel connectivity: the resulting device is called a Digital Cross-connect (DCS) SDH DCS may have only 2 logical ports Pure SDH DCS may connect only STM-1 or higher channels with each other Cross-connects are named after historical patch panels interconnecting regenerator or multiplex section termination devices Pure SDH DCS may not include path termination, switching of channels is typically done at the multiplex section layer 2001, Cisco Systems, Inc. Network Architecture-25

Wideband Digital Crossconnect SDH wideband digital cross-connect (WDCS) is designed for inte