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New Member

Slow file transfer, TCP windows size is too small

Dear everybody

My lan campus has a Cisco C3560-IPBASE-M switch, when i connect 2 laptops into 2 ports, then try to copy a big file via FTP

I see the speed is very slow ( only about 2 - 5 mbps). When i use wireshark to capture i see the TCP windows size is about 200 to 700, and see many TCP dup ACK, TCP fast retransmission, TCP out of order ... ( see the attach file)

- show interface :  speed 100, duplex full, no errors

When i connect 2 laptops directly or via another switch ( ex 2960), the speed is about 95 mbps, TCP windows size is 65535 (maximum ). Everything is excellent.

How do you think about this case, what i should do

Tks so much

------

>sh ver

Cisco IOS Software, C3560 Software (C3560-IPBASE-M), Version 12.2(35)SE5, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Thu 19-Jul-07 18:15 by nachen

Image text-base: 0x00003000, data-base: 0x01100000

ROM: Bootstrap program is C3560 boot loader

BOOTLDR: C3560 Boot Loader (C3560-HBOOT-M) Version 12.2(25r)SEC, RELEASE SOFTWARE (fc4)

W_OFFC_1D_56.8 uptime is 2 years, 36 weeks, 4 days, 8 hours, 35 minutes

System returned to ROM by power-on

System restarted at 07:31:35 Hanoi Tue Mar 1 2011

System image file is "flash:c3560-ipbase-mz.122-35.SE5/c3560-ipbase-mz.122-35.SE5.bin"

cisco WS-C3560-48PS (PowerPC405) processor (revision Q0) with 122880K/8184K bytes of memory.

Processor board ID FDO1251Y0PR

Last reset from power-on

5 Virtual Ethernet interfaces

48 FastEthernet interfaces

4 Gigabit Ethernet interfaces

The password-recovery mechanism is enabled.

512K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address       : 00:24:51:25:68:00

Motherboard assembly number     : 73-9676-14

Power supply part number        : 341-0029-05

Motherboard serial number       : FDO125101SE

Power supply serial number      : LIT124603DA

Model revision number           : Q0

Motherboard revision number     : B0

Model number                    : WS-C3560-48PS-S

System serial number            : FDO1251Y0PR

SFP Module assembly part number : 73-7757-03

SFP Module revision Number      : A0

SFP Module serial number        : FDO12500N5S

Top Assembly Part Number        : 800-25859-04

Top Assembly Revision Number    : C0

Version ID                      : V05

CLEI Code Number                : COMU210ARA

Hardware Board Revision Number  : 0x01

Switch   Ports  Model              SW Version              SW Image

------   -----  -----              ----------              ----------

*    1   52     WS-C3560-48PS      12.2(35)SE5             C3560-IPBASE-M

Configuration register is 0xF

  • LAN Switching and Routing
8 REPLIES
Cisco Employee

Slow file transfer, TCP windows size is too small

Hi Ha Dao,

Do you see high CPU utilization as well during the transfer??

Ideally, the issue would be seen if the traffic is software switched(CPU) instead of hardware switched.

Thanks & Regards,
Karthick Murugan
CCIE#39285

Thanks & Regards, Karthick Murugan CCIE#39285
New Member

Re: Slow file transfer, TCP windows size is too small

hi Karthick, CPU is normal ( about 10 % ), the MAC address table has about 800 entry, i think it is normal too

New Member

Slow file transfer, TCP windows size is too small

note:

- 2 laptops install windows 7

- when i use iperf to test bandwidth i still get the maximum ( 50 Mbps)

Cisco Employee

Re: Slow file transfer, TCP windows size is too small

Hi Ha Dao,

Could you get the output of "show controller utilization | in interface?

Thanks & Regards,
Karthick Murugan
CCIE#39285

Thanks & Regards, Karthick Murugan CCIE#39285
New Member

Re: Slow file transfer, TCP windows size is too small

Sure

show controllers utilization | include Fa0/9

Fa0/9              2                    0

show controllers utilization | include Fa0/10

Fa0/10             0                    2

show inter fa0/9

FastEthernet0/9 is up, line protocol is up (connected)

  Hardware is Fast Ethernet, address is 0024.5125.680b (bia 0024.5125.680b)

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

     reliability 245/255, txload 1/255, rxload 2/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 10/100BaseTX

  input flow-control is off, output flow-control is unsupported

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

  Last input 10w5d, output 00:00:01, output hang never

  Last clearing of "show interface" counters never

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

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 950000 bits/sec, 85 packets/sec

  5 minute output rate 169000 bits/sec, 180 packets/sec

     250423530 packets input, 108599456115 bytes, 0 no buffer

     Received 5988182 broadcasts (0 multicasts)

     0 runts, 290 giants, 0 throttles

     382917 input errors, 89226 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog, 3496032 multicast, 116 pause input

     0 input packets with dribble condition detected

     4088688820 packets output, 773896713239 bytes, 0 underruns

     0 output errors, 0 collisions, 9 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 PAUSE output

     0 output buffer failures, 0 output buffers swapped out

show inter fa0/10

FastEthernet0/10 is up, line protocol is up (connected)

  Hardware is Fast Ethernet, address is 0024.5125.680c (bia 0024.5125.680c)

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

     reliability 255/255, txload 2/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 10/100BaseTX

  input flow-control is off, output flow-control is unsupported

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

  Last input 00:05:57, output 00:00:00, output hang never

  Last clearing of "show interface" counters never

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

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 51000 bits/sec, 68 packets/sec

  5 minute output rate 1055000 bits/sec, 206 packets/sec

     228555869 packets input, 118738348886 bytes, 0 no buffer

     Received 3478516 broadcasts (0 multicasts)

     0 runts, 415 giants, 0 throttles

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

     0 watchdog, 2075695 multicast, 318 pause input

     0 input packets with dribble condition detected

     7313025937 packets output, 982679165445 bytes, 0 underruns

     0 output errors, 0 collisions, 5 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 PAUSE output

     0 output buffer failures, 0 output buffers swapped out

you can see the speed is too slow, i also recapture in wireshark

Cisco Employee

Re: Slow file transfer, TCP windows size is too small

I believe the ingress interface is Fa0/9 which see only 2% of traffic ingressing. Also looking at the "show interface output", I could see low reliability, CRC errors, Input errors. Although they look historical, the reliability is still a concern.

Could you try moving it to a different port or use a different cable?

Thanks & Regards,
Karthick Murugan
CCIE#39285

Thanks & Regards, Karthick Murugan CCIE#39285
New Member

Re: Slow file transfer, TCP windows size is too small

oh my god, tks so much

i don't know why i didn't see it before

Cisco Employee

Re: Slow file transfer, TCP windows size is too small

No worries!!

Try moving to different port and check the status and if it helps please rate all the helpful postings.

Thanks & Regards,
Karthick Murugan
CCIE#39285

Thanks & Regards, Karthick Murugan CCIE#39285
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