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Alcatel Mentoring - Survivability

Alcatel Mentoring - Survivability. Survivability - Contents. CPU Duplication – Internal Principles Multi-ACT CS Duplication - External Introduction Switch over mechanism Double main mode Recommendations eMG Signaling Backup IP link process Overview

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Alcatel Mentoring - Survivability

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  1. Alcatel Mentoring - Survivability

  2. Survivability - Contents • CPU Duplication – Internal • Principles • Multi-ACT • CS Duplication - External • Introduction • Switch over mechanism • Double main mode • Recommendations • eMG Signaling Backup • IP link process • Overview • Signaling backup establishment and release • Media gateway local calls • Inter Media Gateway calls • External calls • IPSLB and duplicated configuration

  3. CPU Duplication (Internal) Overview

  4. CPU duplication - Principles • Principles: • 2 CPUs are running in the system • one in main role • one in active stand by role • The logical role of one CPU doesn’t depend on its physical position (CPU slot) on the back panel • The 2 CPUs exchange data by the back panel, using: • the «C1» link for the telephone redundancy • the Ethernet link for the file transfers CPU A CPU B «C1» link Embedded Ethernet link

  5. CPU duplication - Working principles • In a duplicated system: • Any management is sent from the main CPU to the stand-by CPU • The metering tickets are transferred to the stand-by CPU • The stand-by CPU « knows » the status of each communication • The stand-by CPU « knows » the status of all terminals and couplers

  6. CPU duplication - Working principles • An automatic switch over is performed if: • the main CPU loses the synchronization • A bad sector is found on the main CPU hard drive • The main CPU power supply unit fails • A hardware problem appears in the CPU or in the IO1 IO2/OBCApart of the CPU board • A manual switch over can be performed: • The maintenance command « bascul » can be entered on any CPU (main or stand-by)

  7. INTOF B INTOF B INTOF A INTOF A INTOF A INTOF A Multi-ACT • Example of using INTOFs between 2 ACTs • 4 links max (87 + 87 + 120 + 120 = 414 channels max) main waiting Peripheral ACT INTOF B INTOF B main ACT CPU

  8. Multi-ACT • Example of using INTIPs between 2 ACTs • 2 links max

  9. Call Server Duplication (External)

  10. CS Duplication - Introduction • Purpose: To provide continuous service in the unlikely event of the call server failure • Principle: Two CPUs with the same e-CS software • Main call server • Standby call server • Real time database update from the Main to the Stand-by • Management • Accounting tickets

  11. IP Network Main e-CS Standby e-CS e-MG CS Duplication - Introduction • Main e-CS in service signaling

  12. CS Duplication - Switch over mechanism • If the main call server fails, the system switches to the Stand-by one (which becomes the main) • Because of Call Handling duplication, the calls that are already established are maintained • Calls being connected during switch-over are lost • All calls that are on hold will be sent to the entity call distribution table. • Restrictions • Both e-CS must be on the same platform type • Both e-CS must be located within the same IP sub-network (because of the role IP addressing)

  13. IP Network signaling Main e-CS Standby e-CS e-MG CS Duplication - Switch over mechanism • Loss of the Main e-CS X  Main e-CS

  14. CS Duplication - Switch over mechanism • E-CS roles determination • Call Server initialization • In the OmniPCX Enterprise,the roles are declared for each e-CS • The "Call Server Role" • Primary • Secondary • When initialized, to determine its role, each call server tries to establish a connection with the other one (CONNECT message) • If it succeeds, a negotiation occurs to decide the exact role of each one according to the database parameters • If the Call server role is not correctly defined, the e-CS with the highest IP address starts in Main role

  15. CS Duplication - Switch over mechanism • Once the roles have been determined • There is a "Keep Alive" exchange over IP between the Main and the Standby e-CS • If the Main e-CS goes down or has an IP link problem • The Standby becomes Main • All Media Gateways reconnect to the new Main e-CS

  16. CS Duplication - Double Main mode • If the IP network is down between the two e-CS • Then there are two main Call Servers (double main mode !) • A Real Main and a Pseudo Main • The "Reference Media Gateway" is used to determine the Real Main. Pseudo Main Real Main Node 1 Reference e-MG Node 1 ' e-MG e-MG

  17. CS Duplication - Double Main mode • Services not provided in Double Main mode • Accounting tickets generated on the pseudo Main can not be reported on the other call server • Traffic observation (same thing) • One part of the network has no Voice Mail

  18. CS Duplication - Double Main mode • When the IP network is back • The link between the two Call servers is back • The Pseudo Main Call Server reboots and becomes standby • All the IP devices connected to the Pseudo Main reboot and reconnect to the Real Main • Corresponding communications are lost • A database duplication has to be launched (manually) to bring back consistency between the two call servers

  19. Main ECS StandbyECS Main ECS StandbyECS Main ECS StandbyECS OR Local area Local area CS Duplication - Recommendations • Recommended • Both call servers on the same LAN switch • Call servers on two different LAN switches with inter-switch Link backup

  20. eMG Signaling Backup

  21. e-MG Signaling Backup – Overview • Purpose • To rescue the signaling link between the e-CS and the e-MG in case of IP network breakdown • Implementation • IP Signaling Link Backup (IPSLB) • Mechanism establishing a temporary connection to backup the regular IP link • Communication channel open through the public network for signaling • Use of the GD internal modem (DSP1) • Can not be used for the voice transport

  22. GD "rescuer" DSP1 : GD internal modem Analog or ISDN board Call Server signaling Link Backup e-MG Signaling Backup – Overview • IPSBL principle LAN Public Operator WAN Broken IP signaling Link

  23. e-MG Signaling Backup – Overview • This modem is located in the DSP1 of each GD • It is compatible with V8, V34 and V42 protocols • Restrictions • Each e-MG can only use its local modem (no external modem possible) • Only one connection at a time, in other words, each IPMG can only rescue one IPMG. • Maintenance via the eRMA is not possible during the IPMG signaling back-up.

  24. e-MG Signaling Backup - Establishment • When the IP signaling link to an e-MG is down • The lost e-MG will be considered out of order by the e-CS after a specific timer • The stations and interface boards are not accessible • The established communications are maintained (for a while) • After a timeout (90s by default), the Call server launches the IPSLB process. The lost e-MG also detects that the IP signaling link is down • Looks for a "free modem access" to the public network from another e-MG (rescuer) • The lost e-MG expects to receive an incoming call on a free trunk • When the backup is established, the rescued e-MG boards are reset (except the GD and the board supporting the trunk used to rescue, calls established are released...)

  25. e-MG Signaling Backup - Establishment • If the backup is not establishing or if the regular IP link does not come back • The complete e-MG is lost (reset of the GD) • For the signaling backup, both digital and analog lines can be used • On analog lines, any incoming call is accepted and connected to the local modem • On the ISDN access, a dedicated DID number is needed to connect the call to the local internal modem • Number specified in management and transmitted to the GD at initialization

  26. e-MG Signaling Backup - Release • When the IP network comes back to normal • The IP signaling link is re-established • If it remains stable • The signaling backup is released • The telephone line and the modem used by the IPSLB are released • The Call Handling is informed that e-MG has returned to a normal state • The transition is transparent for the users, no reset of the GD • The established communications are maintained

  27. Backup signaling Call Server Broken IP signaling link Voice e-MG Signaling Backup - Media Gateway Local Calls • Calls within the e-MG are still possible Public Operator IP

  28. Backup signaling Call Server Call forbidden gap Voice flow Impossible call e-MG Signaling Backup - Inter Media Gateway Calls • Communications with the rescued e-MG are forbidden Public Operator IP network core signaling Link Shadow IP network e-MG2 e-MG1

  29. Possible External call Backup signaling Call Server gap  Impossible external call  Impossible external call e-MG Signaling Backup - External Calls • Same principle Public Operator IP IP

  30. IPSLB not established X Call Server Main Call Server Standby Main IP signaling Link e-MG Signaling Backup - IPSLB and Duplicated Configuration • IP network fails between two duplicated e-CS • Both e-CS are active (main) • The IP signaling Link Backup won't be established on a e-Media Gateway which is already exchanging signaling with an e-CS. Public Operator IP network IP network

  31. e-MG Signaling Backup - Restrictions / Remarks • The IPSLB is not able to secure an ACT Media gateway (INTIP B) • No limitation for expansion racks • The HSL link is transparent for the signaling

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