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Cisco Bug: CSCuj42597 - ZBFW: Lots of out-of-order segment drop with HTTP protocol

Last Modified

Dec 12, 2015

Products (1)

  • Cisco Cloud Services Router 1000V Series

Known Affected Releases

15.3(3)S

Description (partial)

Symptom:
The following firewall policy is attached to the firewall zone-pair to allow http transactions:
class-map type inspect match-all http-servers
 match protocol http
!
policy-map type inspect fw-policy
 class type inspect http-servers
  inspect
 class class-default
  drop log

The policy would cause lots of TCP out-of-order segment drops for HTTP flows, especially with long HTTP transactions which require multiple segments to complete the transaction (such as downloading large file from HTTP server); the TCP out-of-order segment drops cause lots of retransmissions, lowering the throughput and at times even causing the request to fail:
csr01#sh platform hardware qfp active feature firewall drop
-------------------------------------------------------------------------------
Drop Reason                                                             Packets
-------------------------------------------------------------------------------
TCP out-of-order segment                                                   6500
Stray Segment                                                                 9

Replacing the class-map with the following using ACL to match HTTP port does not stop the TCP out-of-order segment drops for HTTP flows:
ip access-list extended http-port
 permit tcp any any eq www
!
class-map type inspect match-all http-servers
 match access-group name http-port

Conditions:
Filtering HTTP flows.
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