[cisco-nas] 96K availainle bandwidth vs 128K BW on Vi1 bundle consisting of 2 B-channels during 64K Unrestrictet call via ISDN-TA PPP-multilink to 5350 NAS

[Tassos Chatzithomaoglou]

If the ISDN-TA is connected to the user's PC though a serial (115200) port, then 
this might be "logical".

&y0 wrote on 28/1/2005 1:51 μμ:
> Hi everybody. I have problem while customers places calls to 5350 NAS via
> ISDN using ISDN-TA and PPP-multilink. During the call 2 B-channels are bound
> to Virtual-access interface which parameters then looks like this:
> Router#sh int virtual-access 1
> Virtual-Access1 is up, line protocol is up
>   Hardware is Virtual Access interface
>   MTU 1500 bytes, BW 128 Kbit, DLY 100000 usec,
>      reliability 255/255, txload 1/255, rxload 7/255
>   Encapsulation PPP, loopback not set
>   DTR is pulsed for 5 seconds on reset
>   Time to interface disconnect:  idle 3w3d
>   LCP Open, multilink Open
>   Open: IPCP
>   Last input 00:00:00, output never, output hang never
>   Last clearing of "show interface" counters 02:28:22
>   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
>   Queueing strategy: weighted fair
>   Output queue: 0/1000/64/0 (size/max total/threshold/drops)
>      Conversations  0/50/256 (active/max active/max total)
>      Reserved Conversations 0/0 (allocated/max allocated)
>      Available Bandwidth 96 kilobits/sec
>   30 second input rate 4000 bits/sec, 2 packets/sec
>   30 second output rate 1000 bits/sec, 1 packets/sec
>      32892 packets input, 15179159 bytes, 0 no buffer
>      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
>      31164 packets output, 18584822 bytes, 0 underruns
>      0 output errors, 0 collisions, 0 interface resets
>      0 output buffer failures, 0 output buffers swapped out
>      0 carrier transitions
> Router#sy
>   Interface      User        Mode                     Idle     Peer Address
>   Vi1          fim        Virtual PPP (Bundle) 00:00:06 10.2.2.1
>   Se3/0:1      fim        Sync PPP                    -   Bundle: Vi1
>   Se3/0:2      fim        Sync PPP                    -   Bundle: Vi1
> Accordingly customer can obtain the data transfer speed no more ~88K.
> It looks like 16K is spent for unknown reason per each B-channel as
> arithmetic of 2*(64K-16K)=96K shows I have ever trusted that signalling
> bandwidth should be taken from D-channel bandwidth (in my case
> Serial3/0:15).
> Am I correct? Have anybody solution for this problem? Below is configuration
> of ISDN and D-channel isdn switch-type primary-net5 controller E1 3/0
> framing NO-CRC4  pri-group timeslots 1-31 interface Serial3/0:15  ip
> unnumbered FastEthernet0/0  ip nat inside  encapsulation ppp  load-interval
> 30  dialer idle-timeout 2147483  dialer load-threshold 1 outbound
> dialer-group 1  autodetect encapsulation ppp v120  isdn switch-type
> primary-net5  isdn incoming-voice modem  isdn sending-complete  no cdp
> enable  ppp authentication pap contract_tac  ppp authorization contract_tac
> ppp multilink  ppp timeout multilink link add 1
> 
> --
> AO618-RIPE
> 108248909 
> 
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