Help!Explain the specification of interface

haijason · ‎01-29-2008

Hi,I have a issue about specification of the "show interface vlan ".Could you explain how to calculate the "txload" parameter?

Thanks

mohammedmahmoud · ‎01-29-2008

Hi,

txload and rxload are calculated as a fraction of 255 (255/255 is completely saturated interface), below is an example (i am using a serial interface, but the logic is the same), from the input (114000 bits/sec) and output rates (323000 bits/sec) and the interface BW (1536 Kbit) we can calculate the txload and the rxload as a ratio:

txload = (255 x output rate) / BW

rxload = (255 x input rate) / BW

sh interfaces Serial0/1

Serial0/1 is up, line protocol is up

.

MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,

reliability 255/255, txload 53/255, rxload 18/255

Encapsulation PPP, loopback not set

Keepalive set (10 sec)

LCP Open

Open: IPCP, CDPCP

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

Last clearing of "show interface" counters 2d01h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 45

Queueing strategy: weighted fair

Output queue: 0/1000/64/45 (size/max total/threshold/drops)

Conversations 0/15/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1152 kilobits/sec

30 second input rate 114000 bits/sec, 179 packets/sec

30 second output rate 323000 bits/sec, 196 packets/sec

31555996 packets input, 3245722698 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

33659431 packets output, 2683391659 bytes, 0 underruns

0 output errors, 0 collisions, 1 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

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

BR,

Mohammed Mahmoud.

haijason · ‎01-29-2008

first,thank you for your reply.

Indeed,I want to know how to calculate the vlan interface's BW.

I think maybe there is difference between the physical interface and the logic interface.

mohammedmahmoud · ‎01-29-2008

Hi Shan,

VLAN interfaces have a default BW that varies between platforms (for example the old 3512 uses 10000 Kbit, while the 3560 uses 1000000 Kbit, you can always check it via the show interface vlan x), you can manipulate this values via the bandwidth command under the interface (doing this has nothing to do with the physical speed of the interface let it be a physical or a logical interface).

BR,

Mohammed Mahmoud.

haijason · ‎01-29-2008

sorry, I still have some confusion,can you tell me how to calculate the txload 156/255 ?

___________________________--

Vlan301 is up, line protocol is up

Hardware is EtherSVI, address is 000a.42b3.5800 (bia 000a.42b3.5800)

Description: Link-to-Rcs7513-1

Internet address is 136.31.32.206/30

MTU 4470 bytes, BW 16000 Kbit, DLY 10 usec,

reliability 255/255, txload 156/255, rxload 57/255

Encapsulation ARPA, loopback not set

Keepalive not supported

ARP type: ARPA, ARP Timeout 04:00:00

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

Last clearing of "show interface" counters 5w6d

Input queue: 0/75/459/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 19692000 bits/sec, 12601 packets/sec

5 minute output rate 105044000 bits/sec, 14771 packets/sec

L2 Switched: ucast: 37809177 pkt, 4683972361 bytes - mcast: 2232193 pkt, 243322550 bytes

L3 in Switched: ucast: 28623709383 pkt, 17709262524104 bytes - mcast: 0 pkt, 0 bytes mcast

L3 out Switched: ucast: 17400287840 pkt, 7471416775021 bytes mcast: 0 pkt, 0 bytes

31506251466 packets input, 18311607672072 bytes, 0 no buffer

Received 2232195 broadcasts (0 IP multicasts)

0 runts, 0 giants, 1 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

23156536686 packets output, 8752425131920 bytes, 0 underruns

0 output errors, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

VDubrovskikh · ‎01-29-2008

========

MTU 4470 bytes, BW 16000 Kbit, DLY 10 usec,

reliability 255/255, txload 156/255, rxload 57/255

========

I think ...

txload = (16000Kbit*156)/255 = 9788Kbit per sec

haijason · ‎01-29-2008

oh..

I think txload should be a fraction, such as

156/255.

And I just want to know how can I calculate the value 156/255?

Thanks.