Cisco Systems OL-12518-01 manual Scenario 2-Latency Across the GSR Mpls Core, Throughput

Chapter 4 FCIP over IP/MPLS Core

Testing Scenarios and Results

Where sustained Gigabit throughput is not required (for example, over an OC-12 or slower WAN link), an MTU of 1500 bytes is adequate. Otherwise, use jumbo frames if possible and set the MTU on the Gigabit Ethernet interface to 2300. Also, set the MTU size on the CPE to 2300 bytes. You also need to consider VPN and MPLS headers when configuring MTU size across the path. The MTU size needs to be configured on all routers and switches, including the CPE in the path. The MTU size of 4700 was configured on all PE and P routers to accommodate VPN and MPLS specific headers.

Selective acknowledgement (SACK) is enabled by default in the FCIP profile and should not be turned off. SACK enables the TCP receiver to identify to the sender the contiguous TCP blocks that have been successfully received. The sender can then selectively retransmit only the missing blocks. Figure 4-12shows the result for the throughput testing of the MTU. A full line rate is achieved with packet sizes larger than 1024.

Figure 4-12 Full Line Rate is Achieved with Packet Size Larger than 1024

Through Put testing

	120
	100
put	80
Through	60
	40
	20					132431
	0
	64	128	512	1024	2112	2148

Packet size

Scenario 2—Latency Across the GSR MPLS Core

Figure 4-13shows the average latency with a packet size of 2112.

Figure 4-13 Average Latency—Packet size 2112

Average Latency

Packet size 2112

	1400
(latency)	1200
	1000
	800
usec	600
	400
	200									132432
	0	20	30	40	50	60	70	80	90
	10									100
					Throughput

Data Center High Availability Clusters Design Guide

OL-12518-01 4-25