Any questions? Post'em

Jay, internally we use Ixia as our primary testing platform so I'm hopeful we can help. :)

 

 

I'm sure you're already aware, but I feel compelled to mention this anyway for other folks watching the list: Ixia only reports L7 throughput (i.e. bytes transfered over TCP, excluding TCP/IP/ethernet headers). This means the throughput reporting by Ixia is likely to be ~8% "low" for a throughput test (maybe ~12% for a conn/s test). This is an important point because the wire itself is limited to L2 throughput, so L2 throughput is what really matters from a limits-testing point of view.

 

 

Every single packet has 18 bytes of Ethernet + 20 bytes of IP + 20 bytes of TCP (IP and TCP could have more depending on options), in addition to the actual TCP data. So for a single packet that contains 100 bytes of TCP data, Ixia only reports the "100 bytes", even though the full packet size is at least 100 + 18 + 20 + 20 == 158 bytes. That's the most extreme case, but it proves the point nicely. :)

 

 

An additional relevant detail about gigabit Ethernet is that despite the "1000Mbps" name, only about 996Mbps is technically possible with a standard 1500 byte MTU. The reason for this is simple: gigabit Ethernet takes 12.1us (microseconds) to transmit a a full-size 1518 byte packet (0.51us for 64byte), and Ethernet requires a 0.096us gap between packets. This means the maximum full size packets (1500 bytes + 18 bytes Ethernet) per second is 12.1us + 0.096us divided into 1 second: 1 / (12.1us + 0.096us). The maximum number of packets per second multiplied by 1518 gives you the maximum number of bytes per second, and multiplied by 8, gives you the maximum bits per second, which is roughly 996Mbps.

 

 

This means 7 Gbps line-rate is actually ~6,972Mbps, for example. This means 7 Gbps line-rate using a large-file test is likely to be reported by Ixia as ~6,455 Mbps (this is a very rough estimate).

 

 

Anyway, moving on to your actual question.... :) I have some questions to start, and some suggestions below:

 

1) What BIG-IP version are you using?

 

2) What's TMM CPU utilization?

 

3) How many simusers are configured? (and do you have a simuser constraint set? I suggest a constraint of 1024).

 

 

It should be possitlve to get > 7Gbps with an 8KB response or larger using FastHTTP with default settings, or 64KB+ with standard mode using default settings, regardless of whether your using an HTTP profile (w/ or w/o RAMcache) and/or OneConnect.

 

 

When using FastHTTP (or anytime you're using SNATs) you'll want to make sure BIG-IP has enough self IP addresses so that it won't run out of empheral ports. My standard test config has 20 self IP's on the server-facing VLAN for this purpose. 20 is overkill for almost all needs, but it doesn't hurt. :) Also, this is rarely a factor for large-file throughput tests.

 

 

I also suggest trying the "tcp-lan-optimized" profile to see if that helps. It's also worth looking at your Ixia's TCP send/recv buffer settings. Depending on what version of Ixia you have they might default to 4k , which is clearly far too small to simulate what you'd see from regular Windows/Mac/Linux boxes -- I recommend 64k to start.

 

 

Mike Lowell