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.

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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 Action Purpose
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 Action Purpose
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 Action Purpose
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

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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 .