National Communications System NCS ESF 2 Training Conference NETWORK OPERATIONS INTEROFFICE AND INTER-SWITCH CONNEC

1. National Communications System (NCS)ESF #2 Training ConferenceNETWORK OPERATIONS � INTEROFFICE AND INTER-SWITCH CONNECTIVITY

2. Topics Brief Review of the Local Loop A Look Inside the Network Inter-office Facilities Topology Physical Connectivity Central Office Basics Switching and Call Routing E911 Network Monitoring and Provisioning Network Recovery in Emergency Situations Interoffice Switching E911 Tying it all together

3. The Local Loop Define POTS DLE, multiplexers, SONET RingsDefine POTS DLE, multiplexers, SONET Rings

4. Physical Network Topology

5. Inter-Office Facilities CO�s interconnect via a ring topology using fiber optic cable carrying extremely high bandwidth signals Up to OC-192, (roughly 10Gb/s or 129,024 voice channels in one path) In most cases, these rings interconnect every CO to at least two other CO�s in different directions Signals are transmitted using the SONET (Synchronous Optical NETwork) protocol Allows any circuit to be added or dropped out at any node (CO) on the ring Flexibility of SONET Add/Drop lets us connect any customer in one CO to any customer in another CO. Flexibility of SONET Add/Drop lets us connect any customer in one CO to any customer in another CO.

6. Physical Network Topology -All IOF links are fiber optic cable -all connections are made through a ring structure such that no single failure will fail connectivity between 2 offices-All IOF links are fiber optic cable -all connections are made through a ring structure such that no single failure will fail connectivity between 2 offices

7. Central Office Basics 2 major categories of equipment inside the CO: Switching (provides dial tone and call routing/billing intelligence 2. transport � high capacity lines that interface the IOF network) ex: multiplexer: device that combines many different circuits onto one physical path using a digital bit stream, multiple circuits are interleaved in time [add CO bldg clip art]2 major categories of equipment inside the CO: Switching (provides dial tone and call routing/billing intelligence 2. transport � high capacity lines that interface the IOF network) ex: multiplexer: device that combines many different circuits onto one physical path using a digital bit stream, multiple circuits are interleaved in time [add CO bldg clip art]

8. Central Office Basics Multiplexer � a device used for the transmission of a plurality of information channels over a single transmission medium (Roger L. Freeman) In most cases, this is performed by interleaving multiple digital bit streams in the time domain Cross-connect �an interconnection of two pieces of communications equipment via wires or electronic circuit paths This is typically done in a common equipment bay or frame that provides ready access to any piece of circuitry of a given type, format or bit rate (e.g., DS1, DS3)

9. Physical Connectivity � Inside the CO Concept of cross-connect Mention merging of multiplexer and cross-connect into an electronic cross-connect system or DCS, which performs both functionsConcept of cross-connect Mention merging of multiplexer and cross-connect into an electronic cross-connect system or DCS, which performs both functions

10. Switching Basic functions of a traditional voice switch Provides Dial Tone Recognizes requests for service Collects and analyzes dialed digits (translations) Determines where to send the call (routing) Monitor for feature invocation Disconnect call when customer hangs up Collect traffic/usage data Collect billing data

11. Traditional Switching Network Switching Hierarchy End Office � Local switch (Class 5) Tandem switch (Class 4) No POTS customers Interconnects all local switches in a given geography Point of Interface for other providers such as Long Distance, Wireless and Clef's Handles overflow traffic for local inter-office communications Trunk: The common circuit interface for interoffice switch to switch (and end office to tandem) communication At its lowest level, one �trunk� handles one voice conversation at a time (64Kb/s channel)

12. Switching Connectivity Other providers connect at the tandem level, because it provides the most cost effective access to all of our customers. Many wireless and other service providers are moving toward direct end office trunking because their tandem trunk groups are getting very large.Other providers connect at the tandem level, because it provides the most cost effective access to all of our customers. Many wireless and other service providers are moving toward direct end office trunking because their tandem trunk groups are getting very large.

13. Trunking Concepts Trunk Group A common aggregation of trunks between two switches Individual trunks in a group are called members All trunk groups are engineered (sized) based on expected interoffice traffic between two switches as well as whether or not call traffic destined for the group will be designed with a potential alternate route for call completion Overflow The condition where the traffic hitting the trunk group is larger than the designed capacity of the group. Additional call attempts will either be routed to another trunk group to attempt call completion or be blocked (120 IPM or intercept announcement) Explain 120 IPM and give example of itExplain 120 IPM and give example of it

14. Trunking Concepts � Overflow Trunk Grp AB � is at capacity - 100 members each have a current call At the next call attempt, the switch will attempt to complete the call by connecting the call from A to the tandem, then from the tandem to B This overflow route is pre-engineered and pre-determinedTrunk Grp AB � is at capacity - 100 members each have a current call At the next call attempt, the switch will attempt to complete the call by connecting the call from A to the tandem, then from the tandem to B This overflow route is pre-engineered and pre-determined

15. Making a Trunk Connection End-to-end call connectivity is established using a separate �Signaling� network (overlay) called Signaling System #7 (SS7) Dedicated network for Interoffice Signaling Call setup and routing Trunk selection Continuity testing Designed with significant diversity and redundancy Every switch in the network has at least two signaling links(A-Links), each terminating on a different signaling switch, called a Signal Transfer Point (STP) All STP�s are provisioned as part of a �mated pair� Utilizes a common database and table lookups for certain types of specialized calls 800 toll-free calls Number Portability When signaling is separate from the network this is referred to as Out of band signaling Also called Common Channel Signaling, since all signaling for all calls is done via the same circuit (A link) A Links are so important that even inside the CO, they are routed separately on cable racks, and are on separate multiplexers and take different IOF routes to connect to geographically separated STP�sWhen signaling is separate from the network this is referred to as Out of band signaling Also called Common Channel Signaling, since all signaling for all calls is done via the same circuit (A link) A Links are so important that even inside the CO, they are routed separately on cable racks, and are on separate multiplexers and take different IOF routes to connect to geographically separated STP�s

16. SS7 Network Connectivity

17. Enhanced 911 Overview

18. E911 Concepts and Terms ANI � Automatic Number Identification ALI � Automatic Location Identification PSAP � Public Safety Answering Point ESN � Emergency Service Number

19. E911: How does it work? Overlay network consisting of  Dedicated trunk groups from PSAPs to a 911 tandem switch In this case, the 911 tandem is an end office switch with specialized software in it to handle the PSAP routing Dedicated trunk groups from end office switches to the tandem Engineered at 200% of expected traffic load Data Links from PSAP to the ALI database 911 tandem is an end �office switch, etc. with specialized software to handle ESN routing911 tandem is an end �office switch, etc. with specialized software to handle ESN routing

20. 911 Call Flow Subscriber dials 911 Switch sends ANI to 911 tandem via ES trunk group Tandem looks up the ESN for the calling number Based on ESN, call is routed to the appropriate PSAP via EM trunk group ANI is sent to primary and secondary ALI computers ALI data is retrieved and sent to PSAP by ALI computer and displayed on operator�s console Depending on PSAP equipment, operator may press a single button to transfer the call to the appropriate agency

21. E911 Data and Call Flow ALL Providers input into the 911 DB ES trk grp signaling is now done via SS7, EM trk signaling is done in-band or directly on the trunk itself Who decides what PSAP a customer is connected to THIS IS NON-Trivial ES groups sized for 200% load ALI links are 56K or 64k data circuits ALI computers receive Daily updates from the master 911 DB ALL Providers input into the 911 DB ES trk grp signaling is now done via SS7, EM trk signaling is done in-band or directly on the trunk itself Who decides what PSAP a customer is connected to THIS IS NON-Trivial ES groups sized for 200% load ALI links are 56K or 64k data circuits ALI computers receive Daily updates from the master 911 DB

22. Network Monitoring and Provisioning How do we monitor the condition of the network? Every Network Element (Switch, Multiplexer, Router, etc.) is linked via another overlay network that does nothing but report alarm conditions and situations back to our alarm monitoring centers These Network Reliability Centers are the �eyes and ears� of field operations (24X7) and are responsible for Alarm monitoring and trouble determination Field notification of trouble conditions Failure analysis Restoration coordination In addition to equipment alarm monitoring, we also monitor the condition of our interoffice switch trunking network via a dedicated center that provides real-time traffic analysis and overflow control when network conditions warrant manual intervention

23. Network Monitoring and Provisioning A significant amount of individual circuit provisioning (from a software configuration perspective) is performed via remote access and mechanized processes The rest is handled by manual intervention through dedicated provisioning centers But wire still can�t be provisioned remotely! Remote access for both provisioning and monitoring is via a mix of older point-to-point data circuits riding an X.25 packet switched network and newer IP-based Network Elements Mention loss of Data kit node at bundy road during Katrina and its impact on remote access. All these circuits ride the same IOF that the rest of the network uses. Define what Provisioning IP is preferred, due to reliability, scalability and ability to get performance monitoring data from NE�s, important in proactive maintenance Mention loss of Data kit node at bundy road during Katrina and its impact on remote access. All these circuits ride the same IOF that the rest of the network uses. Define what Provisioning IP is preferred, due to reliability, scalability and ability to get performance monitoring data from NE�s, important in proactive maintenance

24. A Typical Provisioning Order A Wireless carrier requests an additional 24 trunks to be added to an existing trunk group Upon service order input, Operations Support systems go to work Verifying port assignment availability in the master records database Generating required circuit designs that flow into dispatch systems to generate work requests for various departments (Outside tech, CO tech, Provisioning center tech) Inputting provisioning data for the circuits into Network Elements (Switch, Mux, etc.)

25. A Typical Provisioning Order

26. A Typical Provisioning Order Remote Switch Provisioning Physical port assignment Trunk Group Number Member Number Two-way trunk contention protocol Billing Number Remote Mux Provisioning Transmission Protocol Input Port Assignment Output Port Assignment CO Tech Provisioning Wire DSX DS1 Cross-connect Option and Equip Plug-in Circuit Board in the multiplexer Remote Testing Center Perform pre-service testing and cooperative turn-up with Customer

27. Network Recovery in Emergency Conditions

28. Inter-Office Facilities Scenarios Fiber cut in multiple locations A single cut will only result in a simplex condition, not an OOS condition Post Katrina conditions in Slidell required us to lease fiber from a competitor to restore connectivity  Total multiplexer failure (e.g., total power loss to CO) Splice fibers to bypass a node on a ring Lose the ability to drop out service on the ring at this location This was done in Lake Catherine, LA after Katrina to restore connectivity from New Orleans to Slidell Total failures rarely happen � the typical condition experienced is single card failure and a switch to a standby card � no service interruption Possible response Rebuild/Re-splice Temporary microwave links Need data on how many microwave radio links we had at highest point after Katrina Microwave done via internal corporate assets as well as contract vendorsNeed data on how many microwave radio links we had at highest point after Katrina Microwave done via internal corporate assets as well as contract vendors

29. Switching Scenarios Overflow/blocking due to the emergency condition (Call ya mama!) IOF failure causes significant reduction in trunking capacity IOF failure causes loss of both SS7 A-links Total switch failure (e.g., total power loss to CO) Possible responses Add more trunks Change the overflow route (to another group with more capacity) Reconfigure the network to significantly change calling patterns (re-route calls to a different switch or tandem) Restore the switch as quickly as possible In the event of total destruction, bring in a portable switch or digital loop electronics

30. E911 Recovery/Re-routing 5 scenarios 2 Automatic All EM trunks are busy or OOS, call will route to pre-determined alternate PSAP One or more EM trunks to PSAP OOS � Call will route to PSAP through a secondary 911 tandem (if so equipped) 3 Manual PSAP OOS: Selected ESNs may be routed to alternate PSAP as determined by real-time events All ES trunks to tandem are OOS. Calls may be diverted to an alternate number [if IOF trunking is available] End office isolation: Calls may be diverted to a local number Of course, all this assumes that we have good OSP to get a call to the CO. Mirrored tandem arrangement is NOT standard arrangement, but was put in place in NO as a response to Katrina and the problems we hadOf course, all this assumes that we have good OSP to get a call to the CO. Mirrored tandem arrangement is NOT standard arrangement, but was put in place in NO as a response to Katrina and the problems we had

31. E911 Mirrored Tandem ES trunks to different tandems are sized 100% each, with primary and secondary. Prim overflows to secondary.ES trunks to different tandems are sized 100% each, with primary and secondary. Prim overflows to secondary.

32. Putting it All Together

33. CO Equipment Definitions MDF-Main Distributing Frame � Cross-connect field that terminates Switch Line circuits and OSP copper cable pairs DSX-Digital Signal Cross-connect � Cross connect field for high speed digital circuits (DS1/DS3) LGX-Light Guide (Fiber optic) Cross-connect field MUX-interleaves multiple digital signals together over the same circuit � Main interface to IOF network and other service providers DCS � Digital (electronic) Cross-connect � combines the functions of a mux and a cross-connect bay into one device STP-Signal Transfer Point � Signaling System #7 Interoffice voice network trunk signaling switch