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Question : Problem: Packets Out of Order
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We are having a serious problem with some RAD gear that takes TDM voice and
converts it to IP and then back to TDM. The gear (which I don't look after or
know much about) keeps complaining about "packets out of order"..... the
connection is a pair of 6509's and a pair of 2924 switches in between them
using a 100 Meg LAN extension (via local telco).
I ran the ttcp utility between them and get the same issue with packets out of
order but I'm not sure why... looking for input on the below capture..
Thanks,
Paul
gw-6509#ttcp
transmit or receive [receive]:
perform tcp half close [n]:
receive buflen [8192]:
bufalign [16384]:
bufoffset [0]:
port [5001]:
sinkmode [y]:
rcvwndsize [0]:
ack frequency [2]:
delayed ACK [y]: n
show tcp information at end [n]: y
ttcp-r: buflen=8192, align=16384/0, port=5001
rcvwndsize=0, delayedack=no tcp
ttcp-r: accept from 216.168.103.2
ttcp-r: 16777216 bytes in 107768 ms (107.768 real seconds) (~151 kB/s) +++
ttcp-r: 30866 I/O calls
ttcp-r: 0 sleeps (0 ms total) (0 ms average)
Connection state is CLOSEWAIT, I/O status: 1, unread input bytes: 1
Local host: 216.168.100.1, Local port: 5001
Foreign host: 216.168.103.2, Foreign port: 11006
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x4195F05C):
Timer Starts Wakeups Next
Retrans 1 0 0x0
TimeWait 0 0 0x0
AckHold 0 0 0x0
SendWnd 0 0 0x0
KeepAlive 32770 0 0x4196DAB8
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 640436363 snduna: 640436364 sndnxt: 640436364 sndwnd: 4128
irs: 3499076369 rcvnxt: 3515853587 rcvwnd: 3976 delrcvwnd: 152
SRTT: 37 ms, RTTO: 1837 ms, RTV: 1800 ms, KRTT: 0 ms
minRTT: 16 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, retransmission timeout, keepalive running
gen tcbs, no delayed ACK
Datagrams (max data segment is 536 bytes):
Rcvd: 32771 (out of order: 688), with data: 32768, total data bytes: 16777216
Sent: 63452 (retransmit: 0), with data: 0, total data bytes: 0
gw-6509-1#ttcp
transmit or receive [receive]: transmit
Target IP address: 216.168.100.1
perform tcp half close [n]:
send buflen [8192]:
send nbuf [2048]:
bufalign [16384]:
bufoffset [0]:
port [5001]:
sinkmode [y]:
buffering on writes [y]:
show tcp information at end [n]: y
ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5001 tcp -> 216.168.100.1
ttcp-t: connect
ttcp-t: 16777216 bytes in 107768 ms (107.768 real seconds) (~151 kB/s) +++
ttcp-t: 2048 I/O calls
ttcp-t: 0 sleeps (0 ms total) (0 ms average)
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 216.168.103.2, Local port: 11006
Foreign host: 216.168.100.1, Foreign port: 5001
Enqueued packets for retransmit: 7, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x418B9750):
Timer Starts Wakeups Next
Retrans 32257 65 0x418B986F
TimeWait 0 0 0x0
AckHold 0 0 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 3499076369 snduna: 3515850218 sndnxt: 3515853586 sndwnd: 4128
irs: 640436363 rcvnxt: 640436364 rcvwnd: 4128 delrcvwnd: 0
SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 12 ms, maxRTT: 348 ms, ACK hold: 200 ms
Flags: higher precedence, retransmission timeout
Datagrams (max data segment is 536 bytes):
Rcvd: 63443 (out of order: 0), with data: 0, total data bytes: 0
Sent: 32887 (retransmit: 65), with data: 32885, total data bytes: 16836696
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Answer : Problem: Packets Out of Order
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This problem stems from either an improper setup of QOS in the network, or lacking it altogether. What happens is data makes it way through the router bus, and then is divied out as info comes in from multiple sources. Without QOS the data can stay in the buffer until it is grabbed while other data is past through. The caching on some routers are ineffecient simply because TCP/IP is designed with that in mind. You need to use some sort of QOS in order to force certain data through at the required interval.
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