Max Bandwidth on Serial Interface

Unanswered Question
Jul 9th, 2007

This is the show Interface of my 1841 router.

Serial0/0/0 is up, line protocol is up

Hardware is GT96K Serial

Description: PIE

Internet address is 221.120.195.34/30

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input 00:00:00, output 00:00:04, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 6

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/18/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1158 kilobits/sec

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

2662621 packets input, 694448588 bytes, 0 no buffer

Received 47445 broadcasts, 0 runts, 0 giants, 0 throttles

14600 input errors, 14600 CRC, 5407 frame, 3551 overrun, 0 ignored, 5228

ort

2685912 packets output, 344412095 bytes, 0 underruns

0 output errors, 0 collisions, 10 interface resets

0 output buffer failures, 0 output buffers swapped out

8 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

NVI0 is up, line protocol is up

Hardware is NVI

Interface is unnumbered. Using address of NVI0 (0.0.0.0)

MTU 1514 bytes, BW 10000000 Kbit, DLY 0 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation UNKNOWN, loopback not set

Last input never, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 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

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

I want to know is there any limit on my serial interface as I have a 1MB line connected to this interface and I am not been able to utilize the complete bandwidth since the max bust i can reach is of 265Kbps Kindly let me know is there any service provider issue or issue at my side

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Paolo Bevilacqua Mon, 07/09/2007 - 12:36

Hi,

this is most frequently asked question about router. The bandwidth command is purely information for certain routing protocols that likely you don't use, and to calculate the circuit usage in show interface, so whatever value you set for it, it won't change you circuit performance in any manner. Also, the "available bandwidth" is related to QoS configuration that you may or may not be needing.

Now, what happens with you circuit, is that it appears severely errored. Please do "clear counters" and check the errors under serial interface. If these continue to grow, you need to bring up the issue with your ISP or telco, whatever is appropriate.

Another thing that is a little strange, is that you are receiving broadcasts on that interface. Please ask you ISP to turn off any routing protocol that is not used, CDP, etc. These would be unnecessarily taking a little bit of your bandwidth.

Hope this helps, please rate post if it does!

Richard Burts Mon, 07/09/2007 - 12:46

Imran

Based on what is posted here I do not believe that we can determine if there is a service provider issue or an issue on your side. Can you provide details of how you have tested and determined that 265Kbps is the max that you can achieve? What was generating the traffic when you were measuring? It is possible that the limitation is in whatever was generating the traffic (the generator may be limited by disk access speed, by issues with its NIC, by other tasks it was performing at the same time), it is possible that the limitation is in whatever was receiving the traffic (the same set of potential issues as the generator), it is possible that the limitation is in the application being used (TFTP sends relatively small packets, and waits for an acknowledgement before sending the next packet, FTP is dependent on the TCP transmit window and the need to receive an acknowledgement before sending more traffic, or might be impacted by retransmissions).

I note that the interface reports that there have been 14600 input errors. Depending on when these errors occurred they might be part of what is limiting your throughput, especially if they are causing retransmissions.

HTH

Rick

vinay_verma80 Tue, 07/10/2007 - 04:23

hi

the b.w u see in the interface is only used for protocal calculation, ur interface will send date at it's clock rate ,

check the clock seting in ur modem that is connected to the router

i suspect ur clock rate is set to 256k in modem (not router)

regards

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