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Thanks a lot for your input. I'm almost getting there. &nbsp;As far as I understand, routers or network devices can alter a packet's sequence number but are are not able to adjust the TCP SACK information present in the packet. They send the packet to the server without altering the TCP SACK information. The firewall on the server drops the packet as it is unable to relate this packet to the existing connection.<br />
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It is correct. My question is that how can I confirm that &nbsp;it is not adjusting the TCP SACK information. In the packet how do I identify SACK information? Thanks in advance.
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Thanks a lot for your input. I'm almost getting there.  As far as I understand, routers or network devices can alter a packet's sequence number but are are not able to adjust the TCP SACK information present in the packet. They send the packet to the server without altering the TCP SACK information. The firewall on the server drops the packet as it is unable to relate this packet to the existing connection.

It is correct. My question is that how can I confirm that  it is not adjusting the TCP SACK information. In the packet how do I identify SACK information? Thanks in advance.

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Hi,<br />
<br />
I'm running linux box and I can transmit file from server A to &nbsp;B without any prolbem, but if I want to send big file from B to A I need to disable TCP_SACK in A otherwise it goes to stalled mode. I don't want to disablel TCP_SACK. What may be the problem?
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Hi,

I'm running linux box and I can transmit file from server A to  B without any prolbem, but if I want to send big file from B to A I need to disable TCP_SACK in A otherwise it goes to stalled mode. I don't want to disablel TCP_SACK. What may be the problem?

SCP and network issue for big files

The variety of Linux distributions creates myriad issues relating to configuration and operations when computers are networked, not the least of which is the use of various network management applications, some of which are included with specific distributions, while others are standalone applications.

Linux Networking

Networking software modules are interfaced with a framework implemented on the machine's operating system that implements the networking functionality of the operating system. The best known frameworks are the TCP/IP model and the OSI model. Systems typically do not use a single protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a protocol family or protocol suite.[9] Some of the best known protocol suites include: IPX/SPX, X.25, AX.25, AppleTalk and TCP/IP. Other protocols indirectly related to networking include the hypertext transfer protocol (HTTP) and its related technologies, Dynamic Host Configuration Protocol (DHCP), Domain Name Server (DNS) and other Internet protocols.