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BVC
Beginner
Beginner

ISDN 30 E1 configuration

I've recently taken on the care of some ISDN routers that are within the organisation I work for. My knolwedge on ISDN theory and configuration is very limited. From my understanding these routers use an ISDN 30 circuit (E1 line), so they should be using all 30B channels for a 2 Mbit/s. But when I look at the config it says 

!
controller E1 0/1/0
pri-group timeslots 1-8,16
!

Does this command means only channels 1 - 8 are being used? So the router is only getting 576 kbit link (64 kbit/s x 9).

 

After changing the code to pri-group timeslots 1-31 I didn't notice any change in the speed when using pings and live data going across the ISDN. I've included the relevant config. 

 

The router is an ISR 4221. 

 

Any help will be greatly appreciated. 

1 ACCEPTED SOLUTION

Accepted Solutions
Giuseppe Larosa
Hall of Fame Master

Hello @BVC ,

yes the HUB router has a full E1.

Please note that ISDN allows for concurrent calls to the HUB E1 PRI to occur at the same time with each spoke taking some timeslots to create a switched on demand link with the HUB.

This is and was a typical setup.

All the signaling complexity is managed by the ISDN switches.

 

Your understanding is correct about the spoke configuration it should have limited to using only up to 8 data timeslots.

 

In most cases I have seen ISDN was used for backup links only for the fact we had to pay on time using the circuit.

I know that in Germany they have flat fees for ISDN and german colleagues could not take care of minimizing use of ISDN links.

 

Hope to help

Giuseppe

 

View solution in original post

4 REPLIES 4
Giuseppe Larosa
Hall of Fame Master

Hello @BVC ,

 

an E1 is formed by 32 64 kbps sub-channels

the last one is used for framing

channel 16 that is equivalent to ser0/1/0:15 is the D channel where the "intelligence" of the E1 PRI is present Q.931 signaling and above.

All the other channels are called bearer B channels and used to carry data.

 

Now your configuration was that of a fractionary E1 where a subset of timeslots where used 1 to 8 and the D channel.

 

your E1 is connected to a service provider and you shouldn't change the configuration on your side without speaking with the ISDN tech people, because the risk is that if your router after configuration change sends a packet over channel 9 to 30 it can be simply dropped on the service provider side.

 

A fractionary E1 costs less then a full E1, so before making a change you need to verify the actual contract on each E1 line in your network.

 

Hope to help

Giuseppe

 

Hello Giuseppe,

 

Thank you very much I have a greater understanding now. I will get in contact with my manager to understand how many channels the service providers has actually enabled. Just another quick question, the hub router its calling into has the command

 

pri-group timeslots 1-31

 

This means it should have all channels enabled on the ISDN 30 (if the service provider has activated all 30 channels). Can two routers that are using a different number of ISDN channels communicate with each other? Does this mean there could be a bottleneck on the spoke side since the hub could have every channel enabled and is using every channel, while the spoke side only has 8 channels so can only accept the speed that the 8 channel allows?

Giuseppe Larosa
Hall of Fame Master

Hello @BVC ,

yes the HUB router has a full E1.

Please note that ISDN allows for concurrent calls to the HUB E1 PRI to occur at the same time with each spoke taking some timeslots to create a switched on demand link with the HUB.

This is and was a typical setup.

All the signaling complexity is managed by the ISDN switches.

 

Your understanding is correct about the spoke configuration it should have limited to using only up to 8 data timeslots.

 

In most cases I have seen ISDN was used for backup links only for the fact we had to pay on time using the circuit.

I know that in Germany they have flat fees for ISDN and german colleagues could not take care of minimizing use of ISDN links.

 

Hope to help

Giuseppe

 

View solution in original post

Hello Giuseppe,

I've spoken to my manager and it seems like this is correct, we are only suppose to be using 8 channels of the ISDN. Thank you very much for your help though.