Configurable Number of Simultaneous Packets per Flow

In zone-based policy firewalls, the number of simultaneous packets per flow is restricted to 25 and packets that exceed the limit are dropped. The dropping of packets when the limit is reached impacts the performance of networks. The Configurable Number of Simultaneous Packets per Flow feature allows you to configure the number of simultaneous packets per flow from 25 to 100.

This modules provides an overview of the feature and explains how to configure it.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Restrictions for Configurable Number of Simultaneous Packets per Flow

  • When the TCP window scale option is configured, the firewall cannot simultaneously fit too many TCP packets per flow, and packets that exceed the configured limit are dropped. The maximum window size that can be used, if the TCP window scale option is enabled, is 1 GB.

    The standard TCP window size is between 2 and 65,535 bytes. If the TCP payload size is smaller than 655 bytes, 100 simultaneous packets cannot contain all TCP packets that belong to a single TCP window, and this can result in packet drops. We recommend that you increase the TCP payload size or reduce the TCP window size to avoid packet drops.

  • The total available threads in each platform varies according to the enabled license levels. If the configured number of simultaneous packets per flow is bigger than the available hardware thread number, the configuration of simultaneous packets is not effective.

Information About Configurable Number of Simultaneous Packets per Flow

Overview of Configurable Number of Simultaneous Packets per Flow

The Configurable Number of Simultaneous Packets per Flow feature allows you to increase the number of simultaneous packets per flow that can enter a network. You can increase the number of simultaneous packets per flow from 25 to 100. The default is 25 simultaneous packets.

In multithreaded environments, the zone-based policy firewall may simultaneously receive multiple packets for a single traffic flow. During packet processing, the firewall uses two types of locks: flow lock and software lock. The flow lock ensures that packets that belong to the same flow are processed in the correct order. Normal software locks are used when multiple power processing element (PPE) threads try to read or write critical sections or common data structure (for example, memory).

If the number of simultaneous packets per flow is too large, the time taken by a thread to request and acquire a lock may be too long. This latency adversely affects time-critical infrastructure such as resource reuse and heat-beat processing. To control latency, the number of simultaneous packets was restricted to 25, and packets that exceeded 25 were dropped.

However, the dropping of packets drastically impacts system performance of a system. To minimize packet dropping, the Configurable Number of Simultaneous Packets per Flow feature was introduced. You can configure the number of simultaneous packets per flow from 25 to 100.

To change the number of simultaneous packets per flow, you must configure either the parameter-map type inspect parameter-map-name command or the parameter-map type inspect global command, followed by the session packet command. The limit configured under the parameter-map type inspect parameter-map-name command takes precedence over the limit configured under the parameter-map type inspect global command.

The firewall considers Session Initiation Protocol (SIP) trunk traffic as a single session. However, the SIP trunk traffic contains a large number of application-layer gateway (ALG) flows of different users. When the throughput of the SIP trunk traffic is high compared to other traffic, the simultaneous packet limit causes packets to drop and users may experience call drops.

How to Configure the Number of Simultaneous Packets per Flow

Configuring Class Maps and Policy Maps for Simultaneous Packets per Flow

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    class-map type inspect {match-any | match-all} class-map-name

    4.    match protocol protocol-name

    5.    exit

    6.    policy-map type inspect policy-map-name

    7.    class type inspect class-map-name

    8.    inspect

    9.    exit

    10.    class class-default

    11.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example: 
    Device> enable
     

    Enables privileged EXEC mode.

     
    Step 2 configure terminal


    Example: 
    Device# configure terminal
     
    Enters global configuration mode.
    • Enter your password if prompted.
     
    Step 3 class-map type inspect {match-any | match-all} class-map-name


    Example: 
    Device(config)# class-map type inspect match-any cmap-protocols
     

    Creates an inspect-type class map and enters class map configuration mode.

     
    Step 4 match protocol protocol-name


    Example: 
    Device(config-cmap)# match protocol tcp
     

    Configures the match criteria for a class map on the basis of a specified protocol.

     
    Step 5 exit


    Example: 
    Device(config-cmap)# exit
     

    Exits class map configuration mode and returns to global configuration mode.

     
    Step 6 policy-map type inspect policy-map-name


    Example: 
    Device(config)# policy-map type inspect policy1
     

    Creates an inspect-type policy map and enters policy map configuration mode.

     
    Step 7 class type inspect class-map-name


    Example: 
    Device(config-pmap)# class type inspect cmap-protocols
     

    Specifies the traffic class on which an action is to be performed and enters policy-map class configuration mode.

     
    Step 8 inspect


    Example: 
    Device(config-pmap-c)# inspect
     

    Enables stateful packet inspection.

     
    Step 9 exit


    Example: 
    Device(config-pmap-c)# exit
     

    Exits policy-map class configuration mode and returns to policy map configuration mode.

     
    Step 10 class class-default


    Example: 
    Device(config-pmap)# class class-default
     

    Configures or modifies a policy for the default class.

     
    Step 11 end


    Example: 
    Device(config-pmap)# end
     

    Exits policy map configuration mode and returns to privileged EXEC mode.

     

    Configuring the Number of Simultaneous Packets per Flow

    You can configure the number of simultaneous packets per flow after configuring either the parameter-map type inspect command or the parameter-map type inspect global command. The number of simultaneous packets per flow configured under the parameter-map type inspect command overwrites the number configured under the parameter-map type inspect global command.

    You must configure the session packet command to configure the number of simultaneous packets per flow.


    Note
    You must configure either Steps 3 and 4 or Steps 6 and 7.
    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    parameter-map type inspect parameter-map-name

      4.    session packet number-of-simultaneous-packets

      5.    exit

      6.    parameter-map type inspect global

      7.    session packet number-of-simultaneous-packets

      8.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example: 
      Device> enable
       

      Enables privileged EXEC mode.

       
      Step 2 configure terminal


      Example: 
      Device# configure terminal
       
      Enters global configuration mode.
      • Enter your password if prompted.
       
      Step 3 parameter-map type inspect parameter-map-name


      Example: 
      Device(config)# parameter-map type inspect param1
       

      (Optional) Defines an inspect type parameter map, which configures connection thresholds, timeouts, and other parameters pertaining to the inspect action; and enters parameter-map type inspect configuration mode.

       
      Step 4 session packet number-of-simultaneous-packets


      Example: 
      Device(config-profile)# session packet 55
       

      (Optional) Configures the number of simultaneous traffic packets that can be configured per session.

      • Valid values for the number-of-simultaneous-packets argument are 25 to 55.
       
      Step 5 exit


      Example: 
      Device(config-profile)# exit
       

      Exits parameter-map type inspect configuration mode and returns to global configuration mode.

       
      Step 6 parameter-map type inspect global


      Example: 
      Device(config)# parameter-map type inspect global
       

      (Optional) Defines a global inspect parameter map and enters parameter-map type inspect configuration mode.

       
      Step 7 session packet number-of-simultaneous-packets


      Example: 
      Device(config-profile)# session packet 35
       
      (Optional) Configures the number of simultaneous traffic packets that can be configured per session.
      • Valid values for the number-of-simultaneous-packets argument are 25 to 55.
       
      Step 8 end


      Example: 
      Device(config-profile)# end
       

      Exits parameter-map type inspect configuration mode and returns to privileged EXEC mode.

       

      Configuring Zones for Simultaneous Packets per Flow

      This task shows how to configure security zones, a zone pair, and assign interfaces as zone members.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    zone security security-zone

        4.    exit

        5.    zone security security-zone

        6.    exit

        7.    zone-pair security zone-pair-name source source-zone destination destination-zone

        8.    service-policy type inspect policy-map-name

        9.    exit

        10.    interface type number

        11.    zone-member security zone-name

        12.    exit

        13.    interface type number

        14.    zone-member security zone-name

        15.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example: 
        Device> enable
         
        Enables privileged EXEC mode.
        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example: 
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 zone security security-zone


        Example: 
        Device(config)# zone security z1
         
        Creates a security zone to which interfaces can be assigned and enters security zone configuration mode.
        • You need two security zones to create a zone pair: a source zone and a destination zone.
         
        Step 4 exit


        Example: 
        Device(config-sec-zone)# exit
         

        Exits security zone configuration mode and returns to global configuration mode.

         
        Step 5 zone security security-zone


        Example: 
        Device(config)# zone security z2
         
        Creates a security zone to which interfaces can be assigned and enters security zone configuration mode.
        • You need two security zones to create a zone pair: a source zone and a destination zone.
         
        Step 6 exit


        Example: 
        Device(config-sec-zone)# exit
         

        Exits security zone configuration mode and returns to global configuration mode.

         
        Step 7 zone-pair security zone-pair-name source source-zone destination destination-zone


        Example: 
        Device(config)# zone-pair security zp-security source z1 destination z2
         

        Creates a zone pair and enters security zone pair configuration mode.

         
        Step 8 service-policy type inspect policy-map-name


        Example: 
        Device(config-sec-zone-pair)# service-policy type inspect policy1
         

        Attaches a firewall policy map to the destination zone pair.

        • If a policy is not configured between a pair of zones, traffic is dropped by default.
         
        Step 9 exit


        Example: 
        Device(config-sec-zone-pair)# exit
         

        Exits security zone pair configuration mode and returns to global configuration mode.

         
        Step 10 interface type number


        Example: 
        Device(config)# interface gigabitethernet 0/0/0
         

        Configures an interface and enters interface configuration mode.

         
        Step 11 zone-member security zone-name


        Example: 
        Device(config-if)# zone-member security z1
         
        Assigns an interface to a specified security zone.
        • When you make an interface a member of a security zone, all traffic into and out of that interface (except traffic bound for the device or initiated by the device) is dropped by default. To let traffic through the interface, you must make the zone a part of a zone pair to which you apply a policy. If the policy permits traffic, traffic can flow through that interface.
         
        Step 12 exit


        Example: 
        Device(config-if)# exit
         

        Exits interface configuration mode and returns to global configuration mode.

         
        Step 13 interface type number


        Example: 
        Device(config)# interface gigabitethernet 0/0/3
         

        Configures an interface and enters interface configuration mode.

         
        Step 14 zone-member security zone-name


        Example: 
        Device(config-if)# zone-member security z2
         

        Assigns an interface to a specified security zone.

         
        Step 15 end


        Example: 
        Device(config-if)# end
         

        Exits interface configuration mode and returns to privileged EXEC mode.

         

        Configuration Examples for Configurable Number of Simultaneous Packets per Flow

        Example: Configuring Class Maps and Policy Maps for Simultaneous Packets per Flow

        Device# configure terminal
Device(config)# class-map type inspect match-any cmap-protocols
Device(config-cmap)# match protocol tcp
Device(config-cmap)# exit
Device(config)# policy-map type inspect policy1
Device(config-pmap)# class type inspect cmap-protocols
Device(config-pmap-c)# inspect
Device(config-pmap-c)# exit
Device(config-pmap)# class class-default
Device(config-pmap)# end

        Example: Configuring the Number of Simultaneous Packets per Flow

        You can configure the number of simultaneous packets per flow after configuring either the parameter-map type inspect command or the parameter-map type inspect global command. The number of simultaneous packets per flow configured under the parameter-map type inspect command overwrites the number configured under the parameter-map type inspect global command. 

        Device# configure terminal
Device(config)# parameter-map type inspect param1
Device(config-profile)# session packet 55
Device(config-profile)# exit
Device(config)# parameter-map type inspect global
Device(config-profile)# session packet 35
Device(config-profile)# end

        Example: Configuring Zones for Simultaneous Packets per Flow

        Device# configure terminal
Device(config)# zone security z1
Device(config-sec-zone)# exit
Device(config)# zone security z2
Device(config-sec-zone)# exit
Device(config)# zone-pair security zp-security source z1 destination z2
Device(config-sec-zone-pair)# service-policy type inspect policy1
Device(config-sec-zone-pair)# exit
Device(config)# interface gigabitethernet 0/0/0
Device(config-if)# zone-member security z1
Device(config-if)# exit
Device(config)# interface gigabitethernet 0/0/3
Device(config-if)# zone-member security z2
Device(config-if)# end

        Additional References for Configurable Number of Simultaneous Packets per Flow

        Related Documents

        Related Topic

        Document Title

        Cisco IOS commands

        Cisco IOS Master Command List, All Releases

        Firewall commands

        Technical Assistance

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        Feature Information for Configurable Number of Simultaneous Packets per Flow

        The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

        Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
        Table 1 Feature Information for Configurable Number of Simultaneous Packets per Flow

        Feature Name

        Releases

        Feature Information

        Configurable Number of Simultaneous Packets per Flow

        Cisco IOS XE Release 3.11S

        In zone-based policy firewalls, the number of simultaneous packets per flow was restricted to 25, and packets that exceeded the limit were dropped. The dropping of packets when the number is reached impacts network performance. The Configurable Number of Simultaneous Packets per Flow feature allows you to configure the number of simultaneous packets per flow from 25 to 100.

        In Cisco IOS XE Release 3.11S, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers, the Cisco 4400 Series Integrated Services Routers, and the Cisco Cloud Services Routers 1000V Series.

        The following commands were introduced or modified: session packet, show parameter-map type inspect, show platform hardware qfp feature firewall datapath scb, show platform hardware qfp feature firewall zone-pair, and show platform software firewall parameter-map.