Cisco 9134 - MDS Multilayer Fabric Switch Troubleshooting Manual page 429

Chapter 20 Troubleshooting IP Storage Services
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
5 minutes output rate 609420144 bits/sec, 76177518 bytes/sec, 53267 frames/sec
6979248 packets input, 514206826 bytes
55551272 packets output, 79456286344 bytes, 0 underruns
Better throughput can be achieved if the MTU of both the client NIC and the IPS Gigabit Ethernet
interface is changed to a higher MTU, provided the network in the middle supports jumbo frames.
Use the show ips stats tcp CLI command to view TCP statistics (see
value in the segment continues to increase, it shows that either the IP network in the middle has issues
or the TCP peer has problems acknowledging the data that the IPS sends to it. If the MTU of this
interface is higher than the MSS of the iSCSI client, then the split packets value increases. For example,
the client MTU default is 1500, which equates to an MSS value of 1460, but the IPS Gigabit Ethernet
MTU changed to 2500.
Example 20-3 show ips stats tcp Command Output
MDS_BOTTOM# show ips stats tcp interface gigabit 2/1 detail
TCP Statistics for port GigabitEthernet2/1
TCP send stats
0 retransmitted while on ethernet send queue, 0 packets split
3 delayed acks sent
TCP receive stats
TCP Connection Stats
TCP Miscellaneous Stats
TCP SACK Stats
TCP SYN Cache Stats
OL-9285-05
0 multicast frames, 0 compressed
0 input errors, 0 frame, 0 overrun 0 fifo
0 output errors, 0 collisions, 0 fifo
0 carrier errors
56252632 segments, 76746280484 bytes
56100434 data, 152173 ack only packets
1 control (SYN/FIN/RST), 0 probes, 24 window updates
0 segments retransmitted, 0 bytes
7068115 segments, 1061853 data packets in sequence, 54245464 bytes in sequence
0 predicted ack, 187 predicted data
0 bad checksum, 0 multi/broadcast, 0 bad offset
0 no memory drops, 0 short segments
0 duplicate bytes, 0 duplicate packets
0 partial duplicate bytes, 0 partial duplicate packets
0 out-of-order bytes, 0 out-of-order packets
0 packet after window, 0 bytes after window
0 packets after close
7067879 acks, 76746255713 ack bytes, 0 ack toomuch, 21 duplicate acks
0 ack packets left of snd_una, 0 non-4 byte aligned packets
5980106 window updates, 0 window probe
50 pcb hash miss, 0 no port, 0 bad SYN, 0 paws drops
0 attempts, 24 accepts, 24 established
22 closed, 2 drops, 0 conn drops
0 drop in retransmit timeout, 0 drop in keepalive timeout
0 drop in persist drops, 0 connections drained
7054414 segments timed, 7067879 rtt updated
0 retransmit timeout, 0 persist timeout
19 keepalive timeout, 19 keepalive probes
0 recovery episodes, 54218621 data packets, 77791012992 data bytes
0 data packets retransmitted, 0 data bytes retransmitted
1 connections closed, 0 retransmit timeouts
24 entries, 24 connections completed, 0 entries timed out
0 dropped due to overflow, 0 dropped due to RST
0 dropped due to ICMP unreach, 0 dropped due to bucket overflow
Example
Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x
iSCSI TCP Performance Issues
20-3). If the retransmitted
20-55