OCAM8 Flashcards
What is the client signal?
Contains the traffic inputs into the optical network infrastructure. May be optical provider’s internal traffic, another carrier’s traffic or another operational entity
What can the client signal be?
1) A subtending electrical rate signal into a TDM-based NE
2) A lower bit rate optical SONET/SDH signal into higher line rate SONET/SDH NE
3) Any input traffic into a DWDM/CWDM system that operates outside the WDE system’s transport wavelength
What is an OC transport network line?
A network line is the connectivity between network elements. It may be single or multi wavelength and involves more than just the physical fibre: amplifiers, filters and protection schemes may also be included. Lines are responsible for the bulk movement of data across the OC transport network
What is OAM?
Operations, Administration and Maintenance define the process, protocols and applications for managing network equipment are resources. Day to day operations, troubleshooting and network upgrades are part of OAM
What is FCAPS?
Fault, Configuration, Accounting, Performance and Security is the framework that formalises OAM into standard responsibilities that must be enabled, supported and accounted for in an OC network. FCAPS is defined by the Internal Organisation for Standardisation. Is also be defined as Telecommunications Management Network (TMN) by the International Telecommunications Union (ITU)
What is an SLA?
Service Level Agreements are contractual agreement between a service provider and customer to outline the responsibilities and set exceptions and scope for the service provided. Financial penalties are often a component of an SLA.
Define Interexchange Carrier
An IXC is a telephone company that provides connections between local exchanges in different geographical areas
Define Access
A network that serves individuals or groups of homes and businesses
Define Local Area Network
A group of connected devices within the same building or group of buildings. Can be connected to another LAN or a WAN
Why did we evolve to DWDM networks?
DWDM allowed us to increase capacity without having o expand the existing fibre plant.
Compared to SONET/SDH what does DWDM not natively provide?
1) In band communication channels
2) OAM mechanism for alarm and notification
3) SLA supporting mechanism
4) Standardised OAM functionality
What does it mean to support carrier grade reliability?
Support:
1) Network availability, redundancy, resiliency, client signal protection
2) large capacity, standardised OAM, flexible client support, low latency
3) Flexible deployment options: linear, ring and mesh
What is Network Availability?
Based on the Mean Time Between Failures (MTBF) of YEs and the anticipated Mean Time to Repair (MTTR) after failure.
Uptime/total time
What is MTBF?
Vendor specific rating of NEs based in Telcordia standards SR-332 and MIL-HDBK-217
What is MTTR?
An operational rating that describes the duration of failures or the mean time to restore elements to normal operation
What is carrier grade availability?
Expressed as percentage over a year (8,760 hours). Carrier grade is at least 99.999% or 5.26 minutes available across the year.
Availability can be increased using link and NE redundancy
What are the types of redundancy?
1) Path - diverse physical fibre paths
2) NE redundancy - duplicated components
What NE components may be duplicated to offer redundancy?
1) Cards
2) Switch fabric
3) Power supplies
4) Cooling fans
5) Optics
What is Network Resiliency?
Is the network’s reaction to a fault and the ability to maintain the service. The time to detect a failure and report is between 1-10milliseconds. The time to detect and switch over is no more than 50ms
What does it mean for a network to support OAM?
1) Supports performance monitoring
2) Supports SLAs
3) supports FCAPS
What does OAM support?
1) Comprehensive fault detection and isolation
2) Embedded communications channels including GCC/DCC
3) An Optical Supervisory Channel (OSC) to support OAM, SLA and operational goals
How is OAM carried on the client signal?
1) Has area of the client signal mapping structure that allows for carrying OAM information
2) In-Band (along with client signal) - defined by OC transport protocol
3) Out-Of-Band (on separate wavelength) in a DWDM based OC transport network
What is latency?
Latency is time it takes traffic to enter and exit the optical network. It can be affected by serialisation delay or propagation delay
What is serialisation delay?
Time required to modulate the signal onto the fibre. Is affected by protocol but rate and modulation type used
What is propagation delay?
Distance the signal has to travel. Can be slightly different based on the type of fibre used.
Longer routes increase propagation delay
Dispersion compensation also affect propagation delay:
Traditional DC modules increase propagation delay
Electronic DC optics reduce propagation delay
What client signals does an OC transport network have the capability to support?
1) PDH rates
2) Sonet rates
3) Gigabit ethernet rates
4) Fibre channel
5) Fiber connection
6) Video, HD video
7) OTN rates
The more signal support, the greater the flexibility
What is a physical network topology?
The physical arrangement of NEs in the network. An operator will decide on a typology depending on their future needs
What network characteristics affect the choice of topology?
1) Resilience
2) Fault detection capabilities
3) Set up costs
4) Expansion costs
5) Complexity of monitoring services
What are the types of linear topologies?
1) Point to point unprotected line
2) Point to point protect line
3) Point to point with optical trunk switch line
What is a Ring Topology?
NEs are attached to each other in a series to form a ring. Network rings provide resilience to large geographical areas
What is a Mesh Topology?
Each NE is connected to more than one other NE to form a mesh and is enabled by ROADM technology. Mesh can be fully or partially meshed with partially being cheaper by less reliable. Mesh topologies offer high level of network resilience by providing alternative paths to network core. Also if a single device fails, network connectivity ins’t disrupted. Finally, the network can be scaled up without disturbing the existing NEs.
What are types of sites found on DWDM OC transport network?
1) Optical Add/Drop Multiplex (OADM) DWDM
2) Terminal (TOADM) DWDM
3) Reconfiguration OADM (ROADM)
4) Amplifier
What is the difference between an OADM and TOADM site?
OADM sites add/drop some of the operational wavelengths while TOADM add/drop all operational bands
What is a ROADM site?
They reconfigure individual wavelengths remotely using WSS cards. These switch the wavelengths from one path to another photogenically without requiring an O-E-O conversion. A wavelength can be changed on demand without affecting other traffic or services.
What are the benefits of ROADM sites?
1) Can pre-deploy services without a redetermined channel path
2) Reduces line Transponder/Transceiver to ROADM recabling for reduced operating expense
3) Reduces sparing costs
4) Enhances flexibility and scalability
5) Enables new provider offering for clients, such as Optical Virtual Private Networks
What are the applications for OC networks?
1) Distance extension and carrier site interconnectivity
2) Cloud computing
3) Remote storage
4) OVPN
5) Bandwidth grooming
6) Core router offload
What can Distance extension and carrier site interconnectivity provide?
1) Carrier’s the ability to create a network that supports its operation requirements by connecting its physical locations in a geographical region
2) Support connectivity requirements of its customers by supporting new applications and services that require higher capacity
3) Ability to connect cities, countries and continents
What is cloud computing?
Enables the user to access a network of remote servers on the Internet that store and process data. Optical networking provides the high speed transmission required for cloud computing.
What does cloud computing include?
1) Centralised applications, serves and storage
2) Automated provisioning and maintenance
3) Virtual machines and storage
4) Internet access
5) Individualised access
6) Monthly subscription fees Nathan than software purchase or license fees
What is a Storage Area Network (SAN)?
SANs connect data storage devices to customers who wish to store and access stored data. A SAN connects customer’s computers to back up system. This allows for the SAN to transport data to a backup and recover it in the event of a failure. SANs are technological answer to companies who require to store TBs of data. SANs uses an intelligent gateway to tout storage data away from serves and mainframes.
What is OVPN?
OPVNs allow services providers to partition a network virtually by dedicated a network that might include NEs, fibre and wavelengths to a specific customer. The customer is provided with a secure network without the cost of physical infrastructure
What is Bandwidth Grooming?
They group lower-rate signals into a higher signal, so fewer wavelengths on DWDM system and so reducing costs
What is Core Router Offload?
As network core increases, more routers are needed to direct traffic. The optical swiping in ROADMs supports traffic re-direction without the need for expensive routers
How can client signals be handled?
1) Client and line unprotected
2) Client unprotected/ line protected
3) Client and line protected
What is client and line unprotected?
Uses single line and non-redundant equipment, any failure will disrupt the signal. Used for non-critical traffic or client signals are protected by another network provider
What is Client unprotected/ line protected?
The line side is protected by the OC network provider being responsible for protection switching. The point of failure is with client signal or the handoff between the network and client equipment
What is client and line protected?
Requires duplicate client signals from duplicated optics . The network provider is responsible for the physical path redundancy and the customer equipment is responsible for detecting and reacting a network link failure
