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One way throughput problem

asked 2024-09-21 19:30:31 +0000

quazi gravatar image

updated 2024-09-21 21:38:14 +0000

Chuckc gravatar image 
Connectivity:
Host A ----- Switch ----- Router ----- Router ----- Switch ----- Host B

IP:
Host A: 10.10.10.1
Host B: 10.10.10.2

Host A and B are connected through Router and Switch over an EVPN VPWS tunnel. When transferring data from Host B to Host A, not getting throughput more than 20 Mbps in a single session. However, when transferring data in the opposite direction from Host A to Host B, getting 97 Mbps in a single session. There is no packet loss between Routers. Need help to troubleshoot one way throughput issue.

Capture for file transfer from Host B to Host A:
Host A: https://drive.google.com/file/d/1l1yr...
Host B: https://drive.google.com/file/d/1zBp-...

Capture for file transfer from Host A to Host B:
Host A: https://drive.google.com/file/d/1tlt3...
Host B: https://drive.google.com/file/d/1aBDv...

Thank You.

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Those capture files (B>-A files > 200MB; A->B files > 600 MB) are kinda big for analysis.
Can you describe the "transferring data" (protocol, application, type of data) to give some insight to how the files might be pared down.

"Upload_from_10.10.10.2-Capture_from_10.10.10.1.pcapng (241M) is too large for Google to scan for viruses. Would you still like to download this file?"

Chuckc gravatar imageChuckc ( 2024-09-21 21:43:57 +0000 )edit

Good day Chuckc.

File transferred over HTTP (TCP, Port 80) using HTTPFileServer.

For the file transfer from Host B > Host A, I noticed a very high number of tcp.analysis.flags on both sides, but at Host A it is higher (55%) than at Host B (27%). At Host A, TCP Out-of-Order is also relatively high.

However, tcp.analysis.flags for the file transfer session from Host A > Host B are 7% and 2%.

Suspecting Tx path issue from Host B > Host A. Need guidance to identify the actual point of failure and the root cause.

quazi gravatar imagequazi ( 2024-09-22 03:45:59 +0000 )edit

hi

If you plug in Host C in to the same switch where Host A is connected are you able to reproduce the problem? can you do the same test but this time connect Host C to the switch where Host B is connected.

Also can you use iperf for your thruput test and post the results?

net_tech gravatar imagenet_tech ( 2024-09-22 18:56:06 +0000 )edit

Upload_from_10.10.10.2-Capture_from_10.10.10.2.pcapng - 3 way handshake isn't captured

Looks like this is the HTTP server OP is using - > https://sourceforge.net/projects/hfs/...

net_tech gravatar imagenet_tech ( 2024-09-22 20:54:51 +0000 )edit

Hi @net_tech Trying to share the result of the suggested environment using Host C at both side and iperf.

Yes, HFS HTTTP file server used for throughput test.

quazi gravatar imagequazi ( 2024-09-23 08:44:30 +0000 )edit
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answered 2024-09-23 13:37:35 +0000

SYN-bit gravatar image

From a quick glance on the pcap files, I suspect the following:

  • There is quite a bit of packet reordering of the data packets from 10.10.10.2 (Host B) to 10.10.10.1 (Host A).
  • The reordered result in DUP-ACKs
  • Due to the amount of reordering, there are tripple DUP-ACKs, resulting in fast-retranmissions
  • The congestion window will be kept low when there are retransmissions, assuming there was packet-loss due to congestion

Are you able to capture on the WAN (EVPN) side of the routers?

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Not able to capture the WAN side of the routers due to high volume of traffic, 70Gbps usages on 100Gbps link. Only having problem for a specific LAN side connectivity.

quazi gravatar imagequazi ( 2024-09-24 09:28:43 +0000 )edit

you don't need to capture the payload, limit your capture buffer to be slightly larger than the packet header.

net_tech gravatar imagenet_tech ( 2024-09-28 22:46:11 +0000 )edit

Noted with thanks @net_tech.

quazi gravatar imagequazi ( 2024-09-29 12:01:17 +0000 )edit

is MTU set to 9000 on both A and B hosts?

net_tech gravatar imagenet_tech ( 2024-09-29 15:28:21 +0000 )edit

No, both the hosts are in windows default configuration. Host A connected switch jumbo enabled but Host B connected switch in default MTU 1500 and both the routers upstream and downstream ports configured with 9216 MTU.

quazi gravatar imagequazi ( 2024-09-29 16:22:46 +0000 )edit
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Asked: 2024-09-21 19:30:31 +0000

Seen: 108 times

Last updated: Sep 23