Survivability Enhancements

The Survivability Enhancements feature on the Nano CUBE is used to:

  • Monitor the WAN status periodically from the Nano CUBE.

  • Route calls and handle line-seize subscriptions locally when the WAN link is down.

  • Synchronize the registrations with the server when the WAN link is up.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About Survivability Enhancements

Registration through Alias Mapping

The following illustration shows how a phone (with alias mapping) registers to the service provider via Nano CUBE

Figure 1. SIP Phone Registration



The AOR sent in the REGISTER is an alias which is mapped to an extension and/or phone number by the service provider. The service provider returns the mapping details in the 200 OK response sent to the REGISTER. Nano CUBE provides the ability to cache the alias mapping details in its call routing database. When a call is made from the phone, the Request-URI of the INVITE contains the dialed number (short extension or phone number).

If WAN is up, Nano CUBE will always route the INVITE sent from the phone to the service provider without looking up at the alias mapping cache.

If WAN or the service provider is down, that is, in survivability mode, Nano CUBE will route the INVITE locally by looking up at the alias mapping cache.

Alias Mapping—Supported Methods

  1. When the service provider returns the mapping details in the 200 OK message of the REGISTER in the following predefined format:

    Alias

    Extension

    Phone

    alice10000189_1111

    1111

    10000189

  2. The short extension or phone number is embedded in the AOR of the REGISTER. For example, AOR is alice10000189_1111 and the short extension is 1111.

An inbound sip profile can be applied to the REGISTER which extracts the extension part from the AOR and adds a X-CISCO-EXTENSION header.

Nano CUBE when WAN is UP

The following illustration provides an example as to how a typical phone makes a call to another local phone registered in the same server when WAN or the registrar server is up in a typical hosted deployment. The circled numbers in the image indicate the numerical order in which the sequence occurs.

Figure 2. WAN Link is UP - Nano CUBE Deployment

The call flow scenario is as follows: Phone A initiates a call to the Phone B registered to the same server.

  1. Phone A sends an initial INVITE request to Phone B to participate in a call session via Nano CUBE.

  2. Nano CUBE sends this INVITE to the service provider.

  3. The service provider in turn sends the INVITE to Nano CUBE. Since the WAN link is up, the service provider maps details of the user from the register server and provides details of the user, for example, alias of the user, short extension number, and phone number.

  4. Nano CUBE sends INVITE with all the above mentioned information to Phone B.

  5. Phone B sends a 200 OK response to Nano CUBE for the received INVITE.

  6. Nano CUBE sends a 200 OK answer to the service provider.

  7. The service provider responds to Nano CUBE with a 200 OK answer.

  8. A final 200 OK response is sent to Phone A by Nano CUBE and the call is established between Phone A and Phone B.

Example: Normal Mode (WAN is Up in P2P Mode)
CUBE# show sip-ua registration passthrough status

CallId    DirectoryNum   peer     mode   In-Exp      reg-I   Out-Exp   survival
=======   =========      =====    ====   ========    ====    ====      =========
21        NCPhone1006    1        p2p    135 /144     1       144        normal
================================================================================
Example: Normal Mode (WAN is Up in E2E Mode)
CUBE# show sip-ua registration passthrough status

CallId     DirectoryNum   peer   mode     In-Exp      reg-I    Out-Exp  survival
=======    ===========    ====   =====    =====       =====    =======  ========
14574      NCPhone1006    301    e2e      117 /120     --      120      normal
=================================================================================

Nano CUBE Survivability when WAN is Down

In survivability mode, Nano CUBE provides end-to end telephony services when access to the centralized servers is interrupted because of a WAN outage or other factors, like the server being down.

The following illustration shows how a call is established between two end points when WAN link is down during survivability by directly dialing into an extension.

Figure 3. Nano CUBE Survivability when WAN is Down



Earlier, when WAN was down, User A could only contact User B using either the alias or the user-id of User B, and not using their extensions or phone numbers.

Now, in the event the WAN link or registration server is down, when a local call is made, INVITE is sent to Nano CUBE. Nano CUBE maps the details of the user like extension number and phone-number stored during registration. Local phones can now be reached on their short extensions or phone numbers by similar phones subscribed to the server through the same Nano CUBE.

It is possible to register multiple contacts for a single AOR; however, if multiple contacts are registered for a single subscriber, the Nano CUBE uses only the topmost registered contact to deliver the call to that subscriber. For this reason, multiple contacts are not supported.

Example: Survivability Mode in P2P (regsync mode) when WAN is Down
CUBE# show sip-ua registration passthrough status

CallId   DirectoryNum    peer    mode    In-Exp     reg-I  Out-Exp   survival
=======  ========= ============  =====   =========  =====  =======   ========
38       NCPhone1008     1       p2p     3595 /3600   1      3600      regsync
==============================================================================
Example: Survivability Mode in E2E (local fallback mode) when WAN is Down
CUBE# show sip-ua registration passthrough status

CallId   DirectoryNum    peer    mode   In-Exp   reg-I  Out-Exp  survival
=======  ============    ======  ====   =======  =====  =======  ========
70       NCPhone1006     1       e2e    35 /70    --     0       locfall
=========================================================================


CallId   DirectoryNum    peer    mode   In-Exp   reg-I  Out-Exp  survival
=======  ============    ======  ====   =======  =====  =======  ========
513      NCPhone1008     1       e2e    40 /70    --     0       locfall

Different Modes of Survivability Enhancements

The survivability feature addresses the following issues:

  1. When a WAN link or registrar server comes up, it needs to wait till each SIP phone sends the REGISTER message to the server, so that outside phones can reach that phone.

  2. If the phone register timer setting is too large, the outside phone needs to wait that much time to reach that phone, after a link flap.

  3. If the phone register timer setting is too small, it will flood the WAN link.

  4. When the WAN link or registrar server is down, local calls cannot be made.

There are two ways to address these issues:

  • Local fallback

  • Registration synchronization

Local Fallback

  • Nano CUBE does not need to configure credentials, as the phones will trigger registration. Although Nano CUBE receives REGISTER messages for each phone every 5 minutes; for example, it will throttle and send REGISTER messages every 1 hour to the registrar server, avoiding high WAN bandwidth usage. This will address the issues 1, 2, and 3.

  • In normal operation when the WAN link or registrar server is up, the phone’s primary server URL is the registrar server (E2E) registration.

  • "OPTIONS ping" is used to monitor the registrar server link status. When the detected link is down, Nano CUBE will reply with a 500 message and when the phone receives this message, it will send the REGISTER message to Nano CUBE, which is the secondary server (P2P registration). Nano CUBE will reply with a 200 OK message to P2P registration when the link is down. The dial-peer will keep dynamic registrar session target and the local call will not fail. This will address issue 4.

Registration Synchronization

  • If you configure the phones to send REGISTER messages every 1 hour (to help alleviate the WAN link), the NanoCUBE uses the credentials configured to respond to registrar server authentication challenge. This addresses issue 3.

  • When the WAN link or registration server is down (detected by OPTIONS ping), the NanoCUBE keeps the registration database of the SIP phones previously registered successfully, and it does not send REGISTER messages out; NanoCUBE replies with a 200 OK message and dial-peer will keep the dynamic registrar session target. The local call will not fail, addressing issue 4.

  • When the registrar link is up after link flap, the NanoCUBE sends REGISTER message for each phone that was earlier successfully registered to the registrar server. This is throttled to avoid bulk REGISTER messages flooding WAN link as well as the registrar. This addresses issues 1 and 2.

How to Configure Survivability Enhancements

Configuring Local Fallback or Registration Synchronization Globally

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    voice service voip

    4.    sip

    5.    registration passthrough local-fallback tag

    6.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
     Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3voice service voip


    Example:
    Device(config)# voice service voip
     

    Enters voice service VoIP configuration mode.

     
    Step 4sip


    Example:
    Device(conf-voi-serv)# sip
     

    Enters voice service SIP configuration mode.

     
    Step 5registration passthrough local-fallback tag


    Example:
    Device(conf-serv-sip)# registration passthrough local-fallback 10
          		Configures SIP registration passthrough for local fallback mode; this will locally respond to REGISTER in p2p mode when WAN is down. The tag is the WAN link or registrar server dial-peer tag.
    • To configure the registration sync mode, you can use the registration passthrough reg-sync tag command. Use the static keyword to set the phone URL to p2p registration.
     
    Step 6end


    Example:
    Device(conf-serv-sip)# end
     

    Returns to privileged EXEC mode.

     

    Configuring Local Fallback or Registration Synchronization on a Dial Peer

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    dial-peer voice tag voip

      4.    voice-class sip registration passthrough local-fallback tag

      5.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
       Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3dial-peer voice tag voip


      Example:
      Device(config)# dial-peer voice 4 voip
       

      Enters dial peer VoIP configuration mode.

       
      Step 4voice-class sip registration passthrough local-fallback tag


      Example:
      Device(config-dial-peer)# voice-class sip registration passthrough local-fallback 10
              		Configures SIP registration passthrough for local fallback mode; this will locally respond to REGISTER in p2p mode when WAN is down. The tag is the WAN link or registrar server dial-peer tag.
      • To configure the registration sync mode, you can use the voice-class sip registration passthrough reg-sync tag command.
       
      Step 5end


      Example:
      Device(conf-serv-sip)# end
       

      Returns to privileged EXEC mode.

       

      Configuring OPTIONS Ping

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    dial-peer voice tag voip

        4.    voice-class sip options-keepalive up-interval value down-interval value

        5.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
         Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3dial-peer voice tag voip


        Example:
        Device(config)# dial-peer voice 3 voip
         

        Enters dial peer configuration mode.

         
        Step 4voice-class sip options-keepalive up-interval value down-interval value


        Example:
        Device(config-dial-peer)# voice-class sip options-keepalive up-interval 120 down-interval 120
         

        Configures OPTIONS keepalive timer interval for DOWN and UP endpoints.

         
        Step 5end


        Example:
        Device(config-dial-peer)# end
         

        Returns to privileged EXEC mode.

         

        Configuring Registration Timer

        Perform the following task to configure the registration timer in the NanoCUBE rather than on all SIP phones.
        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    voice service voip

          4.    sip

          5.    registrar server expires max value min value

          6.    end


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
           Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2configure terminal


          Example:
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3voice service voip


          Example:
          Device(config)# voice service voip
           

          Enters voice service VoIP configuration mode.

           
          Step 4sip


          Example:
          Device(conf-voi-serv)# sip
           

          Enters voice service SIP configuration mode.

           
          Step 5registrar server expires max value min value


          Example:
          Device(conf-serv-sip)# registrar server expires max 300 min 200
           

          Configures the maximum and minimum time (in seconds) for the registration expiry in NanoCUBE.

          • If the phone sends expiry time as 600 seconds, then the NanoCUBE will reply with 200 OK message and expiry time 300 seconds, and the phone will resend with expiry 300.
           
          Step 6end


          Example:
          Device(conf-serv-sip)# end
           

          Returns to privileged EXEC mode.

           

          Configuring the REGISTER Message Throttling in Nano CUBE

          Perform the following task to throttle the REGISTER message in Nano CUBE.
          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    voice service voip

            4.    sip

            5.    registration passthrough rate-limit expires value local-fallback tag

            6.    end


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
             Device> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.

             
            Step 2configure terminal


            Example:
            Device# configure terminal
             

            Enters global configuration mode.

             
            Step 3voice service voip


            Example:
            Device(config)# voice service voip
             

            Enters voice service VoIP configuration mode.

             
            Step 4sip


            Example:
            Device(conf-voi-serv)# sip
             

            Enters voice service SIP configuration mode.

             
            Step 5registration passthrough rate-limit expires value local-fallback tag


            Example:
            Device(conf-serv-sip)# registration passthrough rate-limit expires 3600 local-fallback 3
             

            Configures the SIP registration passthrough rate-limit expiry value for local-fallback (e2e). Although Nano CUBE receives the REGISTER message every 5 minutes (300 seconds), it will send only one register message every one hour.

            • Under dial peer configuration mode, you can use the voice-class sip registration passthrough rate-limit expires value reg-sync dial-peer-tag command.
             
            Step 6end


            Example:
            Device(conf-serv-sip)# end
             

            Returns to privileged EXEC mode.

             

            Configuring the Class of Restrictions (COR) List

            Perform the following task to configure the COR list to allow the local call to go through the registrar.
            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    dial-peer voice tag voip

              4.    corlist incoming dial-peer

              5.    corlist outgoing dial-peer

              6.    description string

              7.    destination-pattern number

              8.    session protocol sipv2

              9.    session target registrar

              10.    voice-class sip registration passthrough local-fallback tag

              11.    end


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
               Device> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.

               
              Step 2configure terminal


              Example:
              Device# configure terminal
               

              Enters global configuration mode.

               
              Step 3dial-peer voice tag voip


              Example:
              Device(config)# dial-peer voice 3 voip
               

              Enters dial peer configuration mode.

               
              Step 4corlist incoming dial-peer


              Example:
              Device(config-dial-peer)# corlist incoming FromPhone
               

              Specifes the COR to be applied on an incoming dial peer (for incoming calls).

               
              Step 5corlist outgoing dial-peer


              Example:
              Device(config-dial-peer)# corlist outgoing FromSP
               

              Specifes the COR to be applied for outgoing dial peer (for outgoing calls).

               
              Step 6description string


              Example:
              Device(config-dial-peer)# description registration
               

              Adds a description to a dial peer.

               
              Step 7destination-pattern number


              Example:
              Device(config-dial-peer)# destination-pattern 1111
               

              Specifies either the prefix or the full E.164 telephone number to be used for the dial peer.

               
              Step 8session protocol sipv2


              Example:
              Device(config-dial-peer)# session protocol sipv2
               

              Specifies the session protocol for SIP calls between local and remote devices using the packet network.

               
              Step 9session target registrar


              Example:
              Device(config-dial-peer)# session target registrar
               

              Specifies to route the call to the registrar end point for SIP dial peers.

               
              Step 10voice-class sip registration passthrough local-fallback tag


              Example:
              Device(config-dial-peer)# voice-class sip registration passthrough local-fallback 5
               

              Configures SIP registration passthrough for local fallback mode.

               
              Step 11end


              Example:
              Device(config-dial-peer)# end
               

              Returns to privileged EXEC mode.

               

              Verifying Survivability Enhancements

              Perform this task to verify the configurations for the survivability enhancements. The show commands can be entered in any order.

              SUMMARY STEPS

                1.    enable

                2.    show dial-peer voice summary

                3.    show sip-ua registration passthrough status

                4.    show sip-ua register status

                5.    show voip rtp connections

                6.    show call active voice compact


              DETAILED STEPS
                Step 1   enable

                Enables privileged EXEC mode.



                Example:
                Device> enable
                Step 2   show dial-peer voice summary

                Displays the summary information for each voice dial peer.



                Example:
                Device# show dial-peer voice summary

dial-peer hunt 0
             AD                                    PRE PASS                OUT
TAG    TYPE  MIN  OPER PREFIX    DEST-PATTERN      FER THRU SESS-TARGET    STAT PORT    KEEPALIVE
1      voip  up   up             1111...            0  syst registrar
2      voip  up   down           1......            0  syst ipv4:10.104.45.253            busyout
1000   voip  down down           9900...            0  syst ipv4:9.0.0.174:30601
101    voip  down down           1......            0  syst ipv4:10.104.45.31
102    voip  down down           11.....            0  syst ipv4:10.104.45.253
300    voip  down down           .T                 0  syst
400    voip  down down           11110...           0  syst registrar
                Step 3   show sip-ua registration passthrough status

                Displays information about the SIP user agent registration passthrough status. In the sample output shown below, the parameter In-Exp shows the remaining expiry time and the survival field parameters can be regsync, locfall, or normal.



                Example:
                Device# show sip-ua registration passthrough status

CallId       Line         peer         mode In-Exp        reg-I Out-Exp survival
============ ============ ============ ==== ============= ===== ======= ========
5300         1111008      1            e2e  1041  /1200   ----- 1200    normal *
5305         1111002      1            e2e  2847  /3000   ----- 3000    normal *
5311         1111020      1            e2e  1070  /1200   ----- 1200    normal *
================================================================================
                Step 4   show sip-ua register status

                Displays information about the SIP user agent register status.



                Example:
                Device# show sip-ua register status

Line          peer  expires(sec) reg survival P-Associ-URI
========      ===== ============ === ========
11123         23     59          yes regsync
                Step 5   show voip rtp connections

                Displays Real-Time Transport Protocol (RTP) named event packets.



                Example:
                Device# show voip rtp connections

VoIP RTP Port Usage Information:
Max Ports Available: 8091, Ports Reserved: 101, Ports in Use: 2
Port range not configured, Min: 16384, Max: 32767

                                                                                     Ports       Ports       Ports
Media-Address Range                                                                 Available   Reserved    In-use

Default Address-Range                                                                  8091        101         2

VoIP RTP active connections :
No. CallId     dstCallId  LocalRTP RmtRTP LocalIP                                RemoteIP
1     5324       5325       16410    16464  9.40.1.168                             9.40.1.173
2     5325       5324       16412    16528  9.40.1.168                             9.40.1.174
Found 2 active RTP connections
                Step 6   show call active voice compact

                Displays the compact version of the call information for voice calls in progress.



                Example:
                Device# show call active voice compact

<callID>  A/O FAX T<sec> Codec       type        Peer Address       IP R<ip>:<udp>
Total call-legs: 2
      5324 ANS     T9     g711ulaw    VOIP        P1111008       9.40.1.173:16464
      5325 ORG     T9     g711ulaw    VOIP        P1111020       9.40.1.174:16528

                Configuration Examples for Survivability Enhancements

                Example: Configuring Local Fallback Globally

                Device> enable
Device# configure terminal
Device(config)# voice service voip
Device(conf-voi-serv)# sip
Device(conf-serv-sip)# registration passthrough local-fallback 10
Device(config-serv-sip)# end

                Example: Configuring Local Fallback on a Dial Peer

                Device> enable
Device# configure terminal
Device(config)# dial-peer voice 2 voip
Device(config-dial-peer)# voice-class sip registration passthrough local-fallback 10
Device(config-dial-peer)# end

                Example: Configuring OPTIONS Ping

                Device> enable
Device# configure terminal
Device(config)# dial-peer voice 3 voip
Device(config-dial-peer)# voice-class sip options-keepalive up-interval 120 down-interval 120
Device(config-dial-peer)# end

                Example: Configuring the Registration Timer

                Device> enable
Device# configure terminal
Device(config)# voice service voip
Device(conf-voi-serv)# sip
Device(conf-serv-sip)# registrar server expires max 300 min 200
Device(conf-serv-sip)# end

                Example: Configuring REGISTER Message Throttling

                Device> enable
Device# configure terminal
Device(config)# voice service voip
Device(conf-voi-serv)# sip
Device(conf-serv-sip)# registration passthrough rate-limit expires 3600 local-fallback 3
Device(conf-serv-sip)# end

                Example: Configuring the COR List

                Device> enable
Device# configure terminal
Device(config)# dial-peer voice 2 voip
Device(config-dial-peer)# corlist incoming FromPhone
Device(config-dial-peer)# corlist outgoing FromSP
Device(config-dial-peer)# description registration
Device(config-dial-peer)# destination-pattern 1111
Device(config-dial-peer)# session protocol sipv2
Device(config-dial-peer)# session target registrar
Device(config-dial-peer)# voice-class sip registration passthrough local-fallback 5
Device(config-dial-peer)# end

                Feature Information for Survivability Enhancements

                The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

                Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
                Table 1 Feature Information for Survivability Enhancements

                Feature Name

                Releases

                Feature Information

                Survivability Enhancements

                15.3(3)M

                When a WAN link goes down temporarily or the registrar server is down, local calls cannot be made and no calls can be routed to and from the phones. The Survivability Enhancements feature on the NanoCUBE is used to:

                • Monitor the WAN status periodically from the Nano CUBE.

                • Route calls and handle line-seize subscriptions locally when the WAN link is down.

                • Synchronize the registrations with the server when the WAN link is up.

                Survivability Enhancements—Support for Extensions and Phone Numbers

                Cisco IOS 15.6(2)T

                From Cisco IOS 15.6(2)T onwards, when the WAN link or registration server is down, local phones can be reached on their short extensions or phone numbers by similar phones subscribed to the server through the same NANOCUBE.