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The Survivability Enhancements feature on the Nano CUBE is used to:
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The following illustration shows how a phone (with alias mapping) registers to the service provider via Nano CUBE
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.
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 |
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.
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.
The call flow scenario is as follows: Phone A initiates a call to the Phone B registered to the same server.
Phone A sends an initial INVITE request to Phone B to participate in a call session via Nano CUBE.
Nano CUBE sends this INVITE to the service provider.
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.
Nano CUBE sends INVITE with all the above mentioned information to Phone B.
Phone B sends a 200 OK response to Nano CUBE for the received INVITE.
Nano CUBE sends a 200 OK answer to the service provider.
The service provider responds to Nano CUBE with a 200 OK answer.
A final 200 OK response is sent to Phone A by Nano CUBE and the call is established between Phone A and Phone B.
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 ================================================================================
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 =================================================================================
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.
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.
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 ==============================================================================
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
The survivability feature addresses the following issues:
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.
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.
If the phone register timer setting is too small, it will flood the WAN link.
When the WAN link or registrar server is down, local calls cannot be made.
There are two ways to address these issues:
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.
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.
1.
enable
2.
configure terminal
3.
voice service voip
4.
sip
5.
registration passthrough local-fallback tag
6.
end
1.
enable
2.
configure terminal
3.
dial-peer voice tag voip
4.
voice-class sip registration passthrough local-fallback tag
5.
end
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
1.
enable
2.
configure terminal
3.
voice service voip
4.
sip
5.
registrar server expires max value min value
6.
end
1.
enable
2.
configure terminal
3.
voice service voip
4.
sip
5.
registration passthrough rate-limit expires value local-fallback tag
6.
end
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
Perform this task to verify the configurations for the survivability enhancements. The show commands can be entered in any order.
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
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
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
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
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
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
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
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.
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: |
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. |