Google: Difference between revisions

*Take Packet Captures

*Large send offload (LSO) is a technique for increasing egress throughput of high-bandwidth network connections by reducing CPU overhead.

It works by passing a multipacket buffer to the network interface card (NIC).

The NIC then splits this buffer into separate packets.

The technique is also called TCP Segmentation Offload (TSO) when applied to TCP, or generic segmentation offload (GSO).

A similar concept to large segment offload for ingress traffic is large receive offload (LRO).

LSO and LRO are independent and use of one does not require the use of the other.

*Network throughput impacted by TCP window size, Latency and Congestion

*Window Size

Maximum amount of data a sender can send before receiving an acknowledgement.

Standard TCP Window Size = 65K bytes

*It’s not just about latency, TCP doesn’t like congestion

Adding more traffic produces a negative marginal effect above about 30% utilization

*Application is able to generate 10 GBPS traffic? OS limits - CPU - Memory, Network Card speed?

*Window scaling changes the TCP window to:

64KB * 2n (n = window scale factor)

With a window scale factor of 7, which equals a TCP window of 8MB

Single-flow throughput is limited to:

TCP window size / RTT

Without window scaling, TCP is limited to:

64KB / 100ms = 5 Mbps

With CloudBridge default window scale, TCP is limited to:

8MB / 100 ms = 650 Mbps

*WSF 64kB to 8MB

*SACK to minimize data that is resent

*Fast re-transmits to reduce delay before resend