Contents

Managing sessions· 1

About session management 1

Session management operation· 1

Session management functions· 1

Restrictions and guidelines: Session management configuration· 2

Setting the session aging time for different protocol states· 2

Setting the session aging time for different application layer protocols or applications· 3

Specifying persistent sessions· 4

Enabling session synchronization· 4

Enabling session statistics collection software fast forwarding· 5

Enabling top session statistics· 6

Specifying the mode for session state machine· 6

Configuring session logging· 6

Configuring session dual-active mode· 7

Display and maintenance commands for session management 9

 

Managing sessions

About session management

Session management is a common module, providing basic services for NAT, ASPF, and attack detection and protection to implement their session-based services.

Session management defines packet exchanges at transport layer as sessions. It updates session states and ages out sessions according to data flows from the initiators or responders. Session management allows multiple features to process the same service packet.

Session management operation

Session management tracks the session status by inspecting the transport layer protocol information. It performs unified status maintenance and management of all connections based on session tables and relation tables.

When a connection request passes through the device from a client to a server, the device creates a session entry. The entry can contain the request and response information, such as:

·     Source IP address and port number.

·     Destination IP address and port number.

·     Transport layer protocol.

·     Application layer protocol.

·     Protocol state of the session.

A multichannel protocol requires that the client and the server negotiate a new connection based on an existing connection to implement an application. Session management enables the device to create a relation entry for each connection during the negotiation phase. The entry is used to associate the connection with the application. Relation entries will be removed after the associated connections are established.

If the destination IP address of a packet is a multicast IP address, the packet will be forwarded out of multiple ports. When a multicast connection request is received on an inbound interface, the device performs the following operations:

·     Creates a multicast session entry on the inbound interface.

·     Creates a corresponding multicast session entry for each outbound interface.

Unless otherwise stated, "session entry" in this chapter refers to both unicast and multicast session entries.

In actual applications, session management works with security modules to dynamically determine whether a packet can pass the firewall and enter the internal network according to connection status, thus preventing intrusion.

Session management only tracks connection status. It does not block potential attack packets.

Session management functions

Session management enables the device to provide the following functions:

·     Creates sessions for protocol packets, updates session states, and sets aging time for sessions in different protocol states.

·     Supports port mapping for application layer protocols (see "Configuring APR"), enabling application layer protocols to use customized ports.

·     Sets aging time for sessions based on application layer protocols.

·     Supports ICMP/ICMPv6 error packet mapping, enabling the device to search for original sessions according to the payloads in the ICMP/ICMPv6 error packets.

Because error packets are generated due to host errors, the mapping can help speed up the aging of the original sessions.

·     Supports persistent sessions, which are kept alive for a long period of time.

·     Supports session management for the control channels and dynamic data channels of application layer protocols, for example, FTP.

·     Supports real-time synchronization for sessions and for dynamic entries of session-based services, such as NAT, ALG, and ASPF.

Restrictions and guidelines: Session management configuration

For a TCP session in ESTABLISHED state, the priority order of the associated aging time is as follows:

·     Aging time for persistent sessions.

·     Aging time for sessions of application layer protocols.

·     Aging time for sessions in different protocol states.

If the device has excessive sessions, do not set the aging time shorter than the default for a certain protocol state or an application layer protocol. Short aging time settings can make the device slow in response.

Setting the session aging time for different protocol states

About this task

If a session in a certain protocol state has no packet hit before the aging time expires, the device automatically removes the session.

Procedure

1.     Enter system view.

system-view

2.     Set the session aging time for different protocol states.

session aging-time state { fin | icmp-reply | icmp-request | rawip-open | rawip-ready | syn | tcp-close | tcp-est | tcp-time-wait | udp-open | udp-ready } time-value

The default aging time for sessions in different protocol states is as follows:

¡     FIN_WAIT: 30 seconds.

¡     ICMP-REPLY: 30 seconds.

¡     ICMP-REQUEST: 60 seconds.

¡     RAWIP-OPEN: 30 seconds.

¡     RAWIP-READY: 60 seconds.

¡     TCP SYN-SENT and SYN-RCV: 30 seconds.

¡     TCP-CLOSE: 2 seconds.

¡     TCP ESTABLISHED: 3600 seconds.

¡     TCP-TIME-WAIT: 2 seconds.

¡     UDP-OPEN: 30 seconds.

¡     UDP-READY: 60 seconds.

Setting the session aging time for different application layer protocols or applications

About this task

The aging time for sessions of different application layer protocols or applications are valid for TCP sessions in ESTABLISHED state or UDP sessions in READY state. For sessions used by other application layer protocols, the aging time for sessions in different protocol states applies.

Supported application layer protocols or applications specified in this command depend on the APR module. For information about APR, see "Configuring APR."

Procedure

1.     Enter system view.

system-view

2.     Set the session aging time for different application layer protocols.

session aging-time application application-name time-value

By default, the aging time is 1200 seconds for sessions of application layer protocols or applications except for the following sessions:

¡     BOOTPC sessions: 120 seconds.

¡     BOOTPS sessions: 120 seconds.

¡     DNS sessions: 1 second.

¡     FTP sessions: 3600 seconds.

¡     FTP-DATA sessions: 240 seconds.

¡     GPRS-DATA sessions: 60 seconds.

¡     GPRS-SIG sessions: 60 seconds.

¡     GTP-CONTROL sessions: 60 seconds.

¡     GTP-USER sessions: 60 seconds.

¡     H.225 sessions: 3600 seconds.

¡     H.245 sessions: 3600 seconds.

¡     HTTPS sessions: 600 seconds.

¡     ILS sessions: 3600 seconds.

¡     L2TP sessions: 120 seconds.

¡     MGCP-CALLAGENT sessions: 60 seconds.

¡     MGCP-GATEWAY sessions: 60 seconds.

¡     NETBIOS-DGM sessions: 3600 seconds.

¡     NETBIOS-NS sessions: 3600 seconds.

¡     NETBIOS-SSN sessions: 3600 seconds.

¡     NTP sessions: 120 seconds.

¡     PPTP sessions: 3600 seconds.

¡     QQ sessions: 120 seconds.

¡     RAS sessions: 300 seconds.

¡     RIP sessions: 120 seconds.

¡     RSH sessions: 60 seconds.

¡     RTSP session: 3600 seconds.

¡     SCCP sessions: 3600 seconds.

¡     SIP sessions: 300 seconds.

¡     SNMP sessions: 120 seconds.

¡     SNMPTRAP sessions: 120 seconds.

¡     SQLNET sessions: 600 seconds.

¡     STUN sessions: 600 seconds.

¡     SYSLOG sessions: 120 seconds.

¡     TACACS-DS sessions: 120 seconds.

¡     TFTP sessions: 60 seconds.

¡     WHO sessions: 120 seconds.

¡     XDMCP sessions: 3600 seconds.

Specifying persistent sessions

About this task

This task is only for TCP sessions in ESTABLISHED state. You can specify TCP sessions that match the permit statements in the specified ACL as persistent sessions, and set longer lifetime or never-age-out persistent sessions.

A persistent session is not removed until one of the following events occurs:

·     The session entry ages out.

·     The device receives a connection close request from the initiator or responder.

·     You manually clear the session entries.

Procedure

1.     Enter system view.

system-view

2.     Specify persistent sessions.

session persistent acl [ ipv6 ]  acl-number [ aging-time time-value ]

Enabling session synchronization

About this task

This feature enables devices to synchronize sessions and dynamic entries of session-based services. Typically, these devices back up each other and use a virtual IP address to communicate with a peer device. When the primary device fails, a backup device takes over to process and forward service traffic. The failover process is transparent to the peer device, and does not interrupt ongoing services.

This feature also provides automatic backup service for the device. The system automatically backs up session tables and relation tables that are generated by applications that use ALG. These applications include H.323, SIP, and ILS.

Enable session synchronization for DNS and HTTP in the following situations:

·     Users are aware that the current HTTP or DNS sessions will last for a long time.

·     HTTP or DNS session backup is required.

In a network that has asymmetric traffic, heavy service traffic might cause service delay or service unavailable because sessions cannot be backed up timely. For example, one device forwards the TCP SYN packets, and another device forwards its ACK packets. If the session tables of the two devices are not synchronized, the TCP packets will be dropped because of state error. To resolve this issue, enable session synchronization for asymmetric traffic.

Restrictions and guidelines

On an IRF fabric, the NAT configuration is dependent of session synchronization. If session synchronization is enabled, make sure NAT is configured on global interfaces such as aggregate interfaces and redundant interfaces. If you configure NAT on physical ports, disable session synchronization as a best practice.

Procedure

1.     Enter system view.

system-view

2.     Enable session synchronization.

session synchronization enable [ asymmetric ]

By default, session synchronization is disabled.

After session synchronization is enabled, session synchronization is enabled for all application layer protocols except DNS and HTTP by default.

3.     (Optional.) Enable session synchronization for DNS, HTTP, or both.

session synchronization { dns | http }*

By default, session synchronization is disabled for DNS and HTTP.

Enabling session statistics collection software fast forwarding

About this task

This feature enables the device to collect session-based outbound and inbound packets and bytes. You can display session statistics based on different criteria.

·     To display statistics per unicast session, use the display session table command.

·     To display statistics per unicast packet type, use the display session statistics command.

·     To display statistics per multicast session, use the display session table multicast command.

·     To display statistics per multicast packet type, use the display session statistics multicast command.

Procedure

1.     Enter system view.

system-view

2.     Enable session statistics collection for software fast forwarding.

session statistics enable

The default setting varies by device model. For more information, see the command reference.

Enabling top session statistics

About this task

This feature collects the number of sessions for session-based services and ranks the sessions by source address and by destination address separately.

Procedure

1.     Enter system view.

system-view

2.     Enable the top session statistics feature.

session top-statistics enable

By default, the top session statistics feature is disabled.

3.     (Optional.) Display top session statistics.

display session top-statistics { last-1-hour | last-24-hours | last-30-days }

Specifying the mode for session state machine

About this task

When asymmetric-path traffic exists in a hot backup system operating in session active/standby mode, set the mode of session state machine to loose to avoid abnormal traffic loss.

When asymmetric-path traffic exists in a hot backup system operating in session dual-active mode, set the mode of session state machine to compact for disconnected sessions to age out timely.

As a best practice, change the mode of session state machine only when asymmetric-path traffic exists. This feature degrades performance of session-based security check. Make sure you are fully aware of its impact when you use it on a live network.

Procedure

1.     Enter system view.

system-view

2.     Specify the mode for session state machine.

session state-machine mode { compact | loose }

By default, session state machine is in strict mode.

Configuring session logging

About this task

Session logs provide information about user access, IP address translation, and network traffic for security auditing. These logs are sent to the log server or the information center.

The device supports time-based or traffic-based logging:

·     Time-based logging—The device outputs session logs regularly.

·     Traffic-based logging—The device outputs a session log when the traffic amount of a session reaches a threshold only when the session statistics collection for software fast forwarding feature is enabled. After outputting a session log, the device resets the traffic counter for the session. The traffic-based thresholds can be byte-based and packet-based. If you set both thresholds, the last configuration takes effect.

If you set both time-based and traffic-based logging, the device outputs a session log when whichever is reached. After outputting a session log, the device resets the traffic counter and restarts the interval for the session.

If you enable session logging but do not enable logging for session creation or deletion, the device does not output a session log when a session entry is created or removed.

Restrictions and guidelines

The session logging feature must work with the flow log or fast log output feature to generate session logs. Session logs can be output in flow log or fast log output format. By default, they are output in flow log format. For information about flow log and fast log output, see Network Management and Monitoring.

Procedure

1.     Enter system view.

system-view

2.     (Optional.) Set the threshold for time-based session logging.

session log time-active time-value

By default, no threshold is set for time-based session logging.

3.     (Optional.) Set a threshold for traffic-based logging.

session log { bytes-active bytes-value | packets-active packets-value }

By default, no threshold is set for traffic-based logging.

4.     (Optional.) Enable logging for session creation.

session log flow-begin

By default, logging for session creation is disabled.

5.     (Optional.) Enable logging for session deletion.

session log flow-end

By default, logging for session deletion is disabled.

6.     Enter interface view.

interface interface-type interface-number

7.     Enable session logging.

session log enable { ipv4 | ipv6 } [ acl acl-number ] { inbound | outbound }

By default, session logging is disabled.

Configuring session dual-active mode

About this task

In a hot backup system operating in session active/standby mode, only one device processes security services. Session dual-active mode increases load capacity of the system by enabling both devices to process security services.

To balance the service load on the devices, you can use one of the following session creation modes:

·     Hash-based session creation—A session is created on the device to which its first packet is relayed according to the hash result. The device where a session is created might not be the device that receives the traffic. This mode applies if traffic is unevenly distributed among the devices.

·     Local-based session creation—A session is created on the device where the first packet of the session arrives. This mode applies if traffic is evenly distributed among the devices.

In a hot backup system operating in session dual-active mode, a device cannot identify the direction of packets in a UDP traffic flow due to UDP mechanisms. By default, if the return packets of a session do not match any sessions, the device creates a new session. This results in the following issues:

·     If the security control policy permits a UDP traffic flow in one direction, the return packets of the flow are dropped.

·     If the security control policy permits a UDP traffic flow in both directions, two sessions are created for the flow. This affects traffic processing of security services.

To resolve these issues, you can enable transparent transmission for UDP packets. This feature allows a device to relay UDP packets that do not match any sessions to the other device in the hot back system. If the UDP packets also do not match any sessions on the other device, a new session is created locally.

In a hot backup system operating in session dual-active mode, a device can identify the direction of packets in a TCP traffic flow. If the device receives the packets of a new TCP traffic flow, it creates a session. If the return packets of an existing TCP traffic flow do not match any sessions, the device relays the packets to the other device.

Restrictions and guidelines

·     As a best practice, enable transparent transmission for UDP packets only when asymmetric UDP traffic exists in the hot backup system and sessions cannot be synchronized timely. This feature degrades forwarding performance. Make sure you are fully aware of the impact of this feature when you use it on a live network.

·     Transparent transmission for UDP packets takes effect only when local-based session creation is used. If hash-based session creation is used, the devices do not relay UDP packets.

·     In dual-active mode, devices support only Layer 3 forwarding. Layer 2 forwarding is not supported.

·     In dual-active mode, devices support only the flow-based policy for flow classification. For more information about flow classification policies, see multi-CPU packet distribution in Layer 3—IP Services Configuration Guide.

·     AFT is not supported in dual-active mode.

Procedure

1.     Enter system view.

system-view

2.     Enable session dual-active mode.

session dual-active enable

By default, session dual-active mode is disabled. The device is operating in session active/standby mode.

3.     Enable session synchronization.

See "Enabling session synchronization."

4.     Set the session creation mode.

session dual-active create-mode { hash | local }

By default, local-based session creation is used in session dual-active mode.

5.     (Optional.) Enable transparent transmission for UDP packets.

session dual-active transparent udp enable

By default, transparent transmission for UDP packets is disabled in session dual-active mode.

6.     (Optional.) Set the mode of session state machine to compact.

See "Specifying the mode for session state machine."

Display and maintenance commands for session management

 

Execute display commands in any view and reset commands in user view.

 

Task	Command
Display the aging time for sessions of different application layer protocols.	display session aging-time application
Display the aging time for sessions in different protocol states.	display session aging-time state
Display relation table entries.	display session relation-table { ipv4 | ipv6 } [ slot slot-number ]
Display unicast session statistics.	display session statistics [ history-max | summary ] [ slot slot-number ]
Display IPv4 unicast session statistics.	display session statistics ipv4 [ [ responder ] { application application-name | destination-ip destination-ip | destination-port destination-port | destination-zone destination-zone-name | interface interface-type interface-number | protocol { dccp | dns | ftp | gtp | h323 | http | icmp | ils | mgcp | nbt | pptp | raw-ip | rsh | rtsp | sccp | sctp | sip | smtp | sqlnet | ssh | tcp | telnet | tftp | udp | udp-lite | xdmcp } | security-policy-rule rule-name | source-ip source-ip | source-port source-port | source-zone source-zone-name | state { dccp-closereq | dccp-closing | dccp-open | dccp-partopen | dccp-request | dccp-respond | dccp-timewait | icmp-reply | icmp-request | rawip-open | rawip-ready | sctp-closed | sctp-cookie-echoed | sctp-cookie-wait | sctp-established | sctp-shutdown-ack-sent | sctp-shutdown-recd | sctp-shutdown-sent | tcp-close | tcp-close-wait | tcp-est | tcp-fin-wait | tcp-last-ack | tcp-syn-recv | tcp-syn-sent | tcp-syn-sent2 | tcp-time-wait | udp-open | udp-ready | udplite-open | udplite-ready } | vpn-instance vpn-instance-name } * ] [ slot slot-number ]
Display IPv6 unicast session statistics.	display session statistics ipv6 [ [ responder ] { application application-name | destination-ip destination-ip | destination-port destination-port | destination-zone destination-zone-name | interface interface-type interface-number | protocol { dccp | dns | ftp | gtp | h323 | http | icmpv6 | ils | mgcp | nbt | pptp | raw-ip | rsh | rtsp | sccp | sctp | sip | smtp | sqlnet | ssh | tcp | telnet | tftp | udp | udp-lite | xdmcp } | security-policy-rule rule-name | source-ip source-ip | source-port source-port | source-zone source-zone-name | state { dccp-closereq | dccp-closing | dccp-open | dccp-partopen | dccp-request | dccp-respond | dccp-timewait | icmpv6-reply | icmpv6-request | rawip-open | rawip-ready | sctp-closed | sctp-cookie-echoed | sctp-cookie-wait | sctp-established | sctp-shutdown-ack-sent | sctp-shutdown-recd | sctp-shutdown-sent | tcp-close | tcp-close-wait | tcp-est | tcp-fin-wait | tcp-last-ack | tcp-syn-recv | tcp-syn-sent | tcp-syn-sent2 | tcp-time-wait | udp-open | udp-ready | udplite-open | udplite-ready } | vpn-instance vpn-instance-name } * ] [ slot slot-number ]
Display multicast session statistics.	display session statistics multicast [ slot slot-number ]
Display IPv4 unicast session table entries.	display session table ipv4 [ slot slot-number ] [ [ responder ] { application application-name | destination-ip start-destination-ip [ end-destination-ip ] | destination-port destination-port | destination-zone destination-zone-name | interface interface-type interface-number | protocol { dccp | icmp | raw-ip | sctp | tcp | udp | udp-lite } | security-policy-rule rule-name | source-ip start-source-ip [ end-source-ip ] | source-port source-port | source-zone source-zone-name | state { dccp-closereq | dccp-closing | dccp-open | dccp-partopen | dccp-request | dccp-respond | dccp-timewait | icmp-reply | icmp-request | rawip-open | rawip-ready | sctp-closed | sctp-cookie-echoed | sctp-cookie-wait | sctp-established | sctp-shutdown-ack-sent | sctp-shutdown-recd | sctp-shutdown-sent | tcp-close | tcp-close-wait | tcp-est | tcp-fin-wait | tcp-last-ack | tcp-syn-recv | tcp-syn-sent | tcp-syn-sent2 | tcp-time-wait | udp-open | udp-ready | udplite-open | udplite-ready } | vpn-instance vpn-instance-name } * ] [ verbose ]
Display IPv6 unicast session table entries.	display session table ipv6 [ slot slot-number ] [ [ responder ] { application application-name | destination-ip start-destination-ip [ end-destination-ip ] | destination-port destination-port | destination-zone destination-zone-name | interface interface-type interface-number | protocol { dccp | icmpv6 | raw-ip | sctp | tcp | udp | udp-lite } | security-policy-rule rule-name | source-ip start-source-ip [ end-source-ip ] | source-port source-port | source-zone source-zone-name | state { dccp-closereq | dccp-closing | dccp-open | dccp-partopen | dccp-request | dccp-respond | dccp-timewait | icmpv6-reply | icmpv6-request | rawip-open | rawip-ready | sctp-closed | sctp-cookie-echoed | sctp-cookie-wait | sctp-established | sctp-shutdown-ack-sent | sctp-shutdown-recd | sctp-shutdown-sent | tcp-close | tcp-close-wait | tcp-est | tcp-fin-wait | tcp-last-ack | tcp-syn-recv | tcp-syn-sent | tcp-syn-sent2 | tcp-time-wait | udp-open | udp-ready | udplite-open | udplite-ready } | vpn-instance vpn-instance-name } * ] [ verbose ]
Display IPv4 multicast session table entries.	display session table multicast ipv4 [ slot slot-number ] [ [ responder ] { destination-ip start-destination-ip [ end-destination-ip ] | destination-port destination-port | protocol { dccp | icmp | raw-ip | sctp | tcp | udp | udp-lite } | source-ip start-source-ip [ end-source-ip ] | source-port source-port } * ] [ verbose ]
Display IPv6 multicast session table entries.	display session table multicast ipv6 [ slot slot-number ] [ [ responder ] { destination-ip start-destination-ip [ end-destination-ip ] | destination-port destination-port | protocol { dccp | icmpv6 | raw-ip | sctp | tcp | udp | udp-lite } | source-ip start-source-ip [ end-source-ip ] | source-port source-port } * ] [ verbose ]
Display top session statistics.	display session top-statistics { last-1-hour | last-24-hours | last-30-days }
Display statistics about transparently transmitted packets in session dual-active mode.	display session dual-active transparent statistics [ slot slot-number ]
Clear relation table entries.	reset session relation-table [ ipv4 | ipv6 ] [ slot slot-number ]
Clear unicast session statistics.	reset session statistics [ slot slot-number ]
Clear multicast session table entries.	reset session statistics multicast [ slot slot-number ]
Clear IP unicast session table entries.	reset session table [ slot slot-number ]
Clear IPv4 unicast session table entries.	reset session table ipv4 [ slot slot-number ] [ source-ip source-ip ] [ destination-ip destination-ip ] [ protocol { dccp | icmp | raw-ip | sctp | tcp | udp | udp-lite } ] [ source-port  source-port ] [ destination-port destination-port ] [ vpn-instance vpn-instance-name ]
Clear IPv6 unicast session table entries.	reset session table ipv6 [ slot slot-number ] [ source-ip source-ip ] [ destination-ip destination-ip ] [ protocol { dccp | icmpv6 | raw-ip | sctp | tcp | udp | udp-lite } ] [ source-port  source-port ] [ destination-port destination-port ] [ vpn-instance vpn-instance-name ]
Clear IP multicast session table entries.	reset session table multicast [ slot slot-number ]
Clear IPv4 multicast session table entries.	reset session table multicast ipv4 [ slot slot-number ] [ source-ip source-ip ] [ destination-ip destination-ip ] [ protocol { dccp | icmp | raw-ip | sctp | tcp | udp | udp-lite } ] [ source-port  source-port ] [ destination-port destination-port ] [ vpn-instance vpn-instance-name ]
Clear IPv6 multicast session table entries.	reset session table multicast ipv6 [ slot slot-number ] [ source-ip source-ip ] [ destination-ip destination-ip ] [ protocol { dccp | icmpv6 | raw-ip | sctp | tcp | udp | udp-lite } ] [ source-port  source-port ] [ destination-port destination-port ] [ vpn-instance vpn-instance-name ]