FTP bandwidth

[Lewis, Aaron]

I have a dedicated 4meg pipe (3 banded T1s) between two datacenters. I
am running a fully patched MU 4.4 on an alpha with VMS 7.3-2 at point A,
I am sending files to an Integrity running VMS 8.2 & MU 5.1 at point B.



I am maxing out at about 1.5meg( about a single T1). My network guys
have a windows program that shows they can get the full 4meg. How can I
get the full 4meg as well









Thanx

Aaron




Attention:
The information contained in this message and or attachments is
intended only for the person or entity to which it is addressed
and may contain confidential and/or privileged material. Any
review, retransmission, dissemination or other use of, or taking
of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you've
received this in error, please contact the sender and delete the
material from any system and destroy any copies.
--------------------------------------------------------------------------------
This email message has been scanned for Viruses and Content and cleared by NetIQ MailMarshal
--------------------------------------------------------------------------------

[Mike Sullenberger]

Post by Lewis, Aaron
I have a dedicated 4meg pipe (3 banded T1s) between two datacenters. I
am running a fully patched MU 4.4 on an alpha with VMS 7.3-2 at point A,
I am sending files to an Integrity running VMS 8.2 & MU 5.1 at point B.

How do you mean "banded". Are they doing load-balancing at Layer-2
(Multi-link PPP) or at Layer-3 (per-destination or per packet).

If the load-balancing is at Layer-3 and

you are doing per-destination then the max that you can get
from a single TCP connection will be one T1.

you are doing per-destination then theoretically you could
get the total 4 Meg pipe, BUT in this scenario packet can get
out-of-order and TCP may detect needing fast-retransmit which
will reduce the congestion (send window). In which case it
may reduce you to even below a single T1 rate. This also
depends on the round-trip-time.

Post by Lewis, Aaron
I am maxing out at about 1.5meg( about a single T1). My network guys
have a windows program that shows they can get the full 4meg.

I bet the windows application is not TCP or if it is it is not a single
TCP session.

You should also check to see what TCP recieve-window size is being used.
TCP can only transfer 1 receive-window amount of data per round-trip-time.

Max Transfer rate = (Receive-window) / (round-trip-time)

For example:

Receive-window | RTT = 1 ms | 100 ms | 1000 ms |
---------------+------------+---------+---------+
5 KBytes | 5 MBps | 50 KBps | 5 KBps |
---------------+------------+---------+---------+
20 KBytes | 20 MBps | 200 KBps| 20 KBps|
---------------+------------+---------+---------+

To understand more about what is happening I would have to see a sniffer
trace of the TCP transfer. It would be best to use FTP and transfer a
file that is at least 1 MByte.

Mike.

+------------------------------------------------+
| Mike Sullenberger; DSE |
| ***@cisco.com .:|:.:|:. |
| Customer Advocacy CISCO |
+------------------------------------------------+

[Lewis, Aaron]

Mike, this what my network guy says. Also, it was a UDP test they ran
that got the 4meg.

The ima group sends each cell across the next t1. so a packet will have
one cell go across t1 a then the next cell across t1 b then the next
cell across t1 c.

Thanks,
Drew
-----Original Message-----
From: Lewis, Aaron
Sent: Friday, February 15, 2008 7:02 AM
To: Funderburk, Drew
Subject: FW: FTP bandwidth

How are the T1s linked together, see below:

Thanx
Aaron

-----Original Message-----
From: Mike Sullenberger [mailto:***@cisco.com]
Sent: Thursday, February 14, 2008 3:04 PM
To: info-***@process.com
Cc: ***@cisco.com
Subject: Re: FTP bandwidth

Post by Lewis, Aaron
I have a dedicated 4meg pipe (3 banded T1s) between two datacenters. I
am running a fully patched MU 4.4 on an alpha with VMS 7.3-2 at point

A,

Post by Lewis, Aaron
I am sending files to an Integrity running VMS 8.2 & MU 5.1 at point B.

How do you mean "banded". Are they doing load-balancing at Layer-2
(Multi-link PPP) or at Layer-3 (per-destination or per packet).

If the load-balancing is at Layer-3 and

you are doing per-destination then the max that you can get
from a single TCP connection will be one T1.

you are doing per-destination then theoretically you could
get the total 4 Meg pipe, BUT in this scenario packet can get
out-of-order and TCP may detect needing fast-retransmit which
will reduce the congestion (send window). In which case it
may reduce you to even below a single T1 rate. This also
depends on the round-trip-time.

Post by Lewis, Aaron
I am maxing out at about 1.5meg( about a single T1). My network guys
have a windows program that shows they can get the full 4meg.

I bet the windows application is not TCP or if it is it is not a single
TCP session.

You should also check to see what TCP recieve-window size is being used.

TCP can only transfer 1 receive-window amount of data per
round-trip-time.

Max Transfer rate = (Receive-window) / (round-trip-time)

For example:

Receive-window | RTT = 1 ms | 100 ms | 1000 ms |
---------------+------------+---------+---------+
5 KBytes | 5 MBps | 50 KBps | 5 KBps |
---------------+------------+---------+---------+
20 KBytes | 20 MBps | 200 KBps| 20 KBps|
---------------+------------+---------+---------+

To understand more about what is happening I would have to see a sniffer
trace of the TCP transfer. It would be best to use FTP and transfer a
file that is at least 1 MByte.

Mike.

+------------------------------------------------+
| Mike Sullenberger; DSE |
| ***@cisco.com .:|:.:|:. |
| Customer Advocacy CISCO |
+------------------------------------------------+
Attention:
The information contained in this message and or attachments is
intended only for the person or entity to which it is addressed
and may contain confidential and/or privileged material. Any
review, retransmission, dissemination or other use of, or taking
of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you've
received this in error, please contact the sender and delete the
material from any system and destroy any copies.
--------------------------------------------------------------------------------
This email message has been scanned for Viruses and Content and cleared by NetIQ MailMarshal
--------------------------------------------------------------------------------

[Mike Sullenberger]

Post by Lewis, Aaron
Mike, this what my network guy says. Also, it was a UDP test they ran
that got the 4meg.
The ima group sends each cell across the next t1. so a packet will have
one cell go across t1 a then the next cell across t1 b then the next
cell across t1 c.

It sounds like it is layer-2 loadbalancing across the 3 T1 links.

In that case can you have the network guy do a test using FTP and see what
transfer rate he gets.

Can you use TCPDUMP on VMS to collect a trace of the data transfer
that you are trying that is getting the low throughput.

$ multinet tcpdump/num/snap=100/write-binary=transfer-test.tcpd -
host <remote-host-IP>

Then start your transfer in another window.
When the transfer is done stop the tcpdump (^C) and send the file.

Mike.



+------------------------------------------------+
| Mike Sullenberger; DSE |
| ***@cisco.com .:|:.:|:. |
| Customer Advocacy CISCO |
+------------------------------------------------+