Voice gateways, SLT and PGW

[wonderwall_85]

Hi everyone,

I dont know if its the right place to start this discussion so forgive me if i am wrong.

The company in which i am currently wokring is running a call center and IPT as well. i will try to explain the scenario

voicegateways (AS5400 and AS5350 routers with IOS Version 12.4(15)T7)

SLT (2651XM with IOS Version 12.2(8)T10)

PGW (PGW 2200 with SunOS 5.10, MGC)

I was under the impression that if you want to connect PSTN and a voip network you need a PSTN gateway. So why are we using 3 different types of hardware.

Follwing are the explainations in a doucment given to me

the Cisco PGW 2200 provides service providers with the capability to seamlessly route voice and data calls between the PSTN and New  World packet networks.

Cisco 2611 Signaling Link Terminals

(E1 terminates, Take Signaling part and send B n D channels to Voice gateway, Signaling part is resolved by it self and PGW)

Voice Gateways

allows terminals of one type, such as H.323, to communicate with terminals of another type, such as a PBX, by converting protocols. Gateways connect an organization’s network to the PSTN

Any information is much appreciated

[Jonathan Schulenberg]

It appears that you're doing SS7 signaling with the PSTN.

http://www.cisco.com/en/US/products/hw/vcallcon/ps2152/products_data_sheet09186a0080091b58.html

The 2651s are terminating the SS7 signaling, the AS5400 terminates the media, and the PGW2200 is the softswitch controlling it all.

Please remember to rate helpful responses and identify helpful or correct answers.

[wonderwall_85]

Thanks for the reply, Cant we do all this only with Voicegateways? or voice gateway only works for media and cant be use for signaling and controling? btw we are using the PGW in signaling mode no call controlling.

[Daniele Giordano]

Cisco AS has integrated SLT features. So you can use only PGW + AS.

Regards.

[wonderwall_85]

Cant use only AS? even if we only need to do signalling and not controlling?

[Daniele Giordano]

PGW is required only if you are connected to the PSTN via ISUP - SS7 trunk.

If you have ISDN PRI, ISDN BRI, CAS, CCS, etc, you can use only the gateway.

Your gateway is sufficiently smart to understand this type of signalling but not enough to understand SS7.

What type of PSTN connection do you have?

Regards.

[wonderwall_85]

I am under the impression that SS7 and CCS are same, everyone here in my office agree with me. We have SS7/CC7. if there is a difference how can i check which signaling we are using from voicegateways, SLT or PGW?

[Daniele Giordano]

Common Channel Signaling (CCS) is signaling in which one channel in each link is used for signaling to control, account for, and manage traffic on all channels of the link.

CCS is supported by different protocols:

- SS7/C7 or ISUP

- ISDN PRA (primary rate access)

What is your PSTN connection, SS7-ISUP or ISDN?

Can you add the AS config?

Can you check your signaling channel config?

This is for SS7-ISUP trunk:

interface Serial7/0:15

no ip address

encapsulation ss7

channel-id 0

no snmp trap link-status

This is for ISDN:

interface Serial7/0:15

no ip address

no snmp trap link-status

isdn switch-type primary-net5

isdn incoming-voice modem 64

isdn send-alerting

isdn negotiate-bchan

isdn bchan-number-order ascending

isdn sending-complete

no cdp enable

Regards.

[wonderwall_85]

I am pasting some part of the runing config

controller E1 3/0

framing NO-CRC4

pri-group timeslots 1-31 nfas_d primary nfas_int 0 nfas_group 0 rlm-group 0

description ******** SS7 Prepaid CIC Range=289 - 319********

!

controller E1 3/1

framing NO-CRC4

pri-group timeslots 1-31 nfas_d primary nfas_int 0 nfas_group 1 rlm-group 1

description ******** SS7 Prepaid CIC Range=321 - 351********

let me know if this expalins anything.

Someone told me that our PGW is handling ISUP signaling, So i guess its SS7-ISUP. Please let me know.

I really appreciate your responses.

thanks

[wonderwall_85]

Does this help?

interface Dchannel3/1

no ip address

encapsulation hdlc

isdn incoming-voice modem

no isdn send-status-enquiry

isdn negotiate-bchan resend-setup

no cdp enable

let me know how to check my signlaing channel config. thanks.

[Daniele Giordano]

For my experience you don't have SS7 ISUP connection but ISDN NFAS PRI connection: ISDN Non-Facility Associated Signaling (NFAS) allows a single D channel to control multiple Primary Rate Interfaces (PRIs). You can configure a backup D channel when the primary NFAS D channel fails. When you configure the channelized T1 controllers for ISDN PRI, you only need to configure the NFAS primary D channel; its configuration is distributed to all the members of the associated NFAS group. By using a single D channel to control multiple PRIs, one extra channel on each interface is free to carry data traffic. Any hard failure of the primary D-signaling channel results in an immediate switchover to the backup D channel without disconnecting currently connected users.

All is explained here: http://www.cisco.com/en/US/tech/tk801/tk379/technologies_configuration_example09186a00800a6bf2.shtml

You can realize this scenario using PGW as Signalling and Media Controller (signalling backhauling) but PGW is not mandatory.

Others infos and examples here:

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_isdn_voice_configuration_guide/isdn06.html

and here:

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_isdn_voice_configuration_guide/isdn07.html#wp1123885

Probably PGW is required for additional tasks: prepaid, accounting, admission,  billing, real time checks. A single gateway is not sufficiently smart for these features.

Regards.

[wonderwall_85]

Hi there,

Another document says that MTP layer1 and 2 and backhaul by SLT and MTP layer 3 is sent to PGW. Does it means that its SS7-ISUP or you still think its ISDN NFAS PRI. is there any way if i could check this? If there is could you let me know the exact commands to run on the hardware?

thanks again.

[wonderwall_85]

We indeed have an SS7-ISUP to H.323 conneection, confimred by my team lead. Any other info is appreciated. Also if you could guide me how to check the type of signaling on PGW?

thanks

[Gregory Shkolnik]

Convertion of ISUP  to the H.323 could be done with PGW2200+HSI adjunct which was EOLd with PGW2200 altogether.

You have SC2200 (signaling control mode of PGW) converting ISUP/SS7 into the ISDN Q.931 and backhauling it way back to AS5400/AS5350 as NFAS signaling.