MPLS and TCP/UDP transfer

[Shine52]

Have a 45 meg MPLS pipe from NY to LA. Doing simple FTP transfers and having speeds of 200K. Carrier is telling us that we will never exceed TCP transfers of more then 5-6 meg, but right now we are not even getting 1/2 a meg.

UDP tests close to 40 meg. Having a hard time believing this, can anyone shed any light. Is the carrier correct in saying TCP transfers on a 45 meg MPLS pipe never going to exceed 5 meg?

Thanks in advance.

Figure it out damn-it!

 

[jimbopalmer]

<-- has never worked with MPLS

FTP speeds vary with the size of the TCP Receive Window buffer (RWIN). A high speed, high latency pipe, like yours, can get better throughput with higher RWIN. FTP can send many packets of data before receiving the first acknowledgment packet back, but it can never send more packets than the client can hold in it's RWIN buffer. Many OS's have default buffer size that are WAY too small for a transcontinental WAN. Once the server has sent as many packets as fit in the clients RWIN, it sits idle waiting for an ACK, so it can safely send more. A sample run of the tweak tool here hints you may need to "Choose RWIN between 413180 and 1100840" which is much higher than the default.

http://www.dslreports.com/tweaks

http://www.dslreports.com/drtcp

http://episteme.arstechnica.com/eve...36/m/735009307831?r=307001970931#307001970931

I tried to remain child-like, all I acheived was childish.

 

[burtsbees]

Jimbo---can't they actually adjust the window size with an FTP application like CuteFTP or FileZilla? I no longer have these, but I thought that you could...

Shine---200K=200KB, which is 1.6Mb, so it is a little more than one and a half meg. What happens when you do something like map a share and transfer something that way?

Since TCP does have to negotiate the connection, this makes sense to me, especially with the window size. Window size is 98% of it. UDP, there is no ack, syn-ack, syn, fin, etc---just open the port and away you go! Try tftp, which is UDP port 69.

Burt

 

[jimbopalmer]

Burtsbees I am not very much a Windows user, so I am not sure. I have always adjusted Solaris at startup time, and Windows clients via DrTCP.

I tried to remain child-like, all I acheived was childish.

 

[burtsbees]

OK

Burt

 

[Shine52]

I know our FTP sites, going out off the public internet, get 10x's better speeds. This would tell me that our RWIN is able to receive the speeds we are looking for, so the question remains, why would we be getting better speeds over the public internet then the MPLS?

Thanks for the input.

Figure it out damn-it!

 

[rjfoster]

It depends on how your MPLS is configured. Since MPLS will (by design) prioritize traffic by type, your particular MPLS design may restrict FTP traffic to business or economy class.

Assuming you're getting 200 KBs (big K, big B) which, as someone pointed out, is 1.6 Mbps (big M, little b). That's probably not bad since you're probably sharing the MPLS business class with other users.