Lawful Intercept Architecture

LI is the process by which law enforcement agencies (LEAs) conduct electronic surveillance as authorized by judicial or administrative order. Increasingly, legislation is being adopted and regulations are being enforced that require service providers (SPs) and ISPs to implement their networks to explicitly support authorized electronic surveillance. The types of SPs or ISPs that are subject to LI mandates vary greatly from country to country. LI compliance in the United States is specified by the Communications Assistance for Law Enforcement Act (CALEA), and accredited by the Commission on Accreditation for Law Enforcement Agencies.

Cisco supports two architectures for LI: PacketCable and Service Independent Intercept. The LI components by themselves do not ensure customer compliance with applicable regulations but rather provide tools that can be used by SPs and ISPs to construct an LI-compliant network.

The Cisco Service Independent Intercept Architecture Version 3.0 document describes implementation of LI for VoIP networks using the Cisco Broadband Telephony Softswitch (BTS) 10200 Softswitch call agent, version 5.0, in a non-PacketCable network. Packet Cable Event Message specification version 1.5-I01 is used to deliver the call identifying information along with version 2.0 of the Cisco Tap MIB for call content.

The Cisco Service Independent Intercept Architecture Version 2.0 document describes implementation of LI for VoIP networks using the Cisco BTS 10200 Softswitch call agent, versions 4.4 and 4.5, in a non-PacketCable network. Although not a PacketCable network, PacketCable Event Messages Specification version I08 is still used to deliver call identifying information, along with version 1.0 or version 2.0 of the Cisco Tap MIB for call content. The Cisco Service Independent Intercept Architecture Version 2.0 document adds additional functionality for doing data intercepts by both IP address and session ID, which are both supported in version 2.0 of the Cisco Tap MIB (CISCO-TAP2-MIB).

The Cisco Service Independent Intercept Architecture Version 1.0 document describes implementation of LI for VoIP networks that are using the Cisco BTS 10200 Softswitch call agent, versions 3.5 and 4.1, in a non-PacketCable network. Although not a PacketCable network, PacketCable Event Message Specification version I03 is still used to deliver call identifying information, along with version 1.0 of the Cisco Tap MIB (CISCO-TAP-MIB) for call content. Simple data intercepts by IP address are also discussed.

The PacketCable Lawful Intercept Architecture for BTS Version 5.0 document describes the implementation of LI for VoIP using Cisco BTS 10200 Softswitch call agent, version 5.0, in a PacketCable network that conforms to PacketCable Event Messages Specification version 1.5-I01.

The PacketCable Lawful Intercept Architecture for BTS Versions 4.4 and 4.5 document describes the implementation of LI for VoIP using Cisco BTS 10200 Softswitch call agent, versions 4.4 and 4.5, in a PacketCable network that conforms to PacketCable Event Messages Specification version I08.

The PacketCable Lawful Intercept Architecture for BTS Versions 3.5 and 4.1 document describes the implementation of LI for VoIP using Cisco BTS 10200 Softswitch call agent, versions 3.5 and 4.1, in a PacketCable network that conforms to PacketCable Event Message Specification version I03.

The PacketCable Control Point Discovery Interface Specification document defines an IP-based protocol that can be used to discover a control point for a given IP address. The control point is the place where Quality of Service (QoS) operations, LI content tapping operations, or other operations may be performed.

The Cisco ASR 1000 series routers support two types of LI: regular and broadband (per-subscriber). Broadband wiretaps are executed on access subinterfaces. Regular wiretaps are executed on access subinterfaces and physical interfaces. Wiretaps are not required, and are not executed, on internal interfaces. The router determines which type of wiretap to execute based on the interface that the target's traffic is using.

LI on the Cisco ASR 1000 series routers can intercept traffic based on a combination of one or more of the following fields:

• Destination IP address and mask (IPv4 or IPv6 address)
• Destination port or destination port range
• Source IP address and mask (IPv4 or IPv6 address)
• Source port or source port range
• Protocol ID
• Type of Service (TOS)
• Virtual routing and forwarding (VRF) name, which is translated to a vrf-tableid value within the router.
• Subscriber (user) connection ID

The LI implementation on the Cisco ASR 1000 series routers is provisioned using SNMP3 and supports the following functionality:

• Interception of communication content. The router duplicates each intercepted packet and then places the copy of the packet within a UDP-header encapsulated packet (with a configured CCCid). The router sends the encapsulated packet to the LI mediation device. Even if multiple lawful intercepts are configured on the same data flow, only one copy of the packet is sent to the mediation device. If necessary, the mediation device can duplicate the packet for each LEA.
• Interception of IPv4 and IPv6 flows.
• Interception of IPv4 and IPv6 multicast flows, where the target is the source of the multicast traffic.

VRF Aware LI is the ability to provision a LI wiretap on IPv4 data in a particular Virtual Private Network (VPN). This feature allows a LEA to lawfully intercept targeted data within that VPN. Only IPv4 data within that VPN is subject to the VRF-based LI tap.

VRF Aware LI is available for the following types of traffic:

• ip2ip
• ip2tag (IP to MPLS)
• tag2ip (MPLS to IP)

To provision a VPN-based IPv4 tap, the LI administrative function (running on the mediation device) uses the CISCO-IP-TAP-MIB to identify the name of the VRF table that the targeted VPN uses. The VRF name is used to select the VPN interfaces on which to enable LI in order to execute the tap.

The router determines which traffic to intercept and which mediation device to send the intercepted packets based on the VRF name (along with the source and destination address, source and destination port, and protocol).

Note	When using the Cisco-IP-TAP-MIB, if the VRF name is not specified in the stream entry, the global IP routing table is used by default.

The Lawful Intercept feature enables you to configure the system so that IP packets that are sent and received on ATM interfaces are intercepted based on the PVC information, such as the Virtual Path Identifier (VPI) or Virtual Channel Identifier (VCI). If you specify an interface when configuring the system, then all IP traffic on the given interface corresponding to the VPI or VCI on the ATM PVC is intercepted. If you do not specify an interface when configuring the system, then IP traffic corresponding to the ATM PVC on all interfaces is intercepted.

LI of IP traffic on ATM interfaces is available for the following interfaces and encapsulation types:

• ATM interface
• ATM multipoint interface
• ATM subinterface point-to-point
• PPP over ATM (PPPoA) encapsulation
• PPP over Ethernet over ATM (PPPoEoA) encapsulation

To provision an IP traffic tap on an ATM interface, the LI administrative function (running on the mediation device) uses the CISCO-IP-TAP-MIB to specify the VPI and VCI information for ATM PVCs. This information is used to select the interfaces on which to enable LI in order to execute the tap.

The router determines which traffic to intercept and to which mediation device to send the intercepted packets based on the VPI and VCI information.

When an ATM interface tap is provisioned, the system creates an IP_STREAM entry type, that stores all tap information (such as the PVC information and interface). The LI feature intercepts packets at the IP layer. If the interface is an ATM interface, LI extracts the PVC information from the packet and matches it against the provisioned streams. If an interface is specified when configuring the system, LI also matches the packet information against the interface. For each matching stream, the LI module sends a copy of the packet to the corresponding mediation device.

To configure IPv6 based lawful intercepts, the system identifies either the source or destination address as the target address and then determines if a less specific route to the target address exists. If a less specific route to the target address exists, the system identifies the list of interfaces that can used to reach the target address and applies the intercepts to those interfaces only.

The system automatically detects route changes and reapplies intercepts on any changed routes.

The system uses the IPv6 stream details specified by the snmp set command to identify the target address, using the following criteria:

• If the source address prefix length is 0, the destination address is chosen as the target address. Likewise, if the destination address prefix length is 0, the source address is chosen as the target address.
• If neither the source address nor destination address prefix length is 0, the address with the longer prefix length is chosen as the target address.
• If the prefix lengths of the source address and destination address are equal, then the system determines which network is close to the Content IAP (CIAP) by doing a longest match lookup on the prefix in the IPv6 routing table. The system chooses the location (source or destination) with the longer prefix as the target.

Due to its sensitive nature, the Cisco LI MIBs are only available in software images that support the LI feature. These MIBs are not accessible through the Network Management Software MIBs Support page ( http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml ).

• Restricting Access to the Lawful Intercept MIBs
  

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server view view-name MIB-name included

4.    snmp-server view view-name MIB-name included

5.    snmp-server view view-name MIB-name included

6.    snmp-server view view-name MIB-name included

7.    snmp-server view view-name MIB-name included

8.    snmp-server group group-name v3 auth read view-name write view-name

9.    snmp-server user user-name group-name v3 auth md5 auth-password

10.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	snmp-server view view-name MIB-name included Example: Router(config)# snmp-server view exampleView ciscoTap2MIB included	Creates an SNMP view that includes the CISCO-TAP2-MIB (where exampleViewis the name of the view to create for the MIB). This MIB is required for both regular and broadband lawful intercept.
Step 4	snmp-server view view-name MIB-name included Example: Router(config)# snmp-server view exampleView ciscoIpTapMIB included	Adds the CISCO-IP-TAP-MIB to the SNMP view.
Step 5	snmp-server view view-name MIB-name included Example: Router(config)# snmp-server view exampleView cisco802TapMIB included	Adds the CISCO-802-TAP-MIB to the SNMP view.
Step 6	snmp-server view view-name MIB-name included Example: Router(config)# snmp-server view exampleView ciscoUserConnectionTapMIB included	Adds the CISCO-USER-CONNECTION-TAP-MIB to the SNMP view.
Step 7	snmp-server view view-name MIB-name included Example: Router(config)# snmp-server view exampleView ciscoMobilityTapMIB included	Adds the CISCO-MOBILITY-TAP-MIB to the SNMP view.
Step 8	snmp-server group group-name v3 auth read view-name write view-name Example: Router(config)# snmp-server group exampleGroup v3 auth read exampleView write exampleView	Creates an SNMP user group that has access to the LI MIB view and defines the group's access rights to the view.
Step 9	snmp-server user user-name group-name v3 auth md5 auth-password Example: Router(config)# snmp-server user exampleUser exampleGroup v3 auth md5 examplePassword	Adds users to the specified user group.
Step 10	end Example: Router(config)# end	Exits the current configuration mode and returns to privileged EXEC mode.

• Where to Go Next
  

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server host ip-address community-string udp-port port notification-type

4.    snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart

5.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	snmp-server host ip-address community-string udp-port port notification-type Example: Router(config)# snmp-server host 10.2.2.1 community-string udp-port 161 udp	Specifies the IP address of the mediation device and the password-like community-string that is sent with a notification request. For lawful intercept, the udp-port must be 161 and not 162 (the SNMP default).
Step 4	snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart Example: Router(config)# snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart	Configures the router to send RFC 1157 notifications to the mediation device. These notifications indicate authentication failures, link status (up or down), and router restarts.
Step 5	end Example: Router(config)# end	Exits the current configuration mode and returns to privileged EXEC mode.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    no snmp-server enable traps

4.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	no snmp-server enable traps Example: Router(config)# no snmp-server enable traps	Disables all SNMP notification types that are available on your system.
Step 4	end Example: Router(config)# end	Exits the current configuration mode and returns to privileged EXEC mode.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    aaa intercept

4.    aaa authentication ppp default group radius

5.    aaa accounting delay-start all

6.    aaa accounting send stop-record authentication failure

7.    aaa accounting network default start-stop group radius

8.    radius-server attribute 44 include-in-access-req

9.    radius-server host host-name

10.    aaa server radius dynamic-author

11.    client ip-address

12.    domain {delimiter character| stripping [right-to-left]}

13.    server-key word

14.    port port-number

15.    exit

16.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	aaa intercept Example: Router(config)# aaa intercept	Enables lawful intercept on the router. Associate this command with a high administrative security to ensure that unauthorized users cannot stop intercepts if this command is removed.
Step 4	aaa authentication ppp default group radius Example: Router(config)# aaa authentication ppp default group radius	Specifies the authentication method to use on the serial interfaces that are running Point-to-Point protocol (PPP). Note    This command is required because tap information resides only on the RADIUS server. You can authenticate with locally configured information, but you cannot specify a tap with locally configured information.
Step 5	aaa accounting delay-start all Example: Router(config)# aaa accounting delay-start all	Delays the generation of accounting start records until the user IP address is established. Specifying the all keyword ensures that the delay applies to all VRF and non-VRF users. Note    This command is required so that the mediation device can see the IP address assigned to the target.
Step 6	aaa accounting send stop-record authentication failure Example: Router(config)# aaa accounting send stop-record authentication failure	(Optional) Generates accounting stop records for users who fail to authenticate while logging into or during session negotiation. Note    If a lawful intercept action of 1 does not start the tap, the stop record contains Acct-Termination-Cause, attribute 49, set to 15 (Service Unavailable).
Step 7	aaa accounting network default start-stop group radius Example: Router(config)# aaa accounting network default start-stop group radius	(Optional) Enables accounting for all network-related service requests. Note    This command is required only to determine the reason why a tap did not start.
Step 8	radius-server attribute 44 include-in-access-req Example: Router(config)# radius-server attribute 44 include-in-access-req	(Optional) Sends RADIUS attribute 44 (Accounting Session ID) in access request packets before user authentication (including requests for preauthentication). Note    Enter this command to obtain attribute 44 from the Access-Request packet. Otherwise you will have to wait for the accounting packets to be received before you can determine the value of attribute 44.
Step 9	radius-server host host-name Example: Router(config)# radius-server host host1	(Optional) Specifies the RADIUS server host.
Step 10	aaa server radius dynamic-author Example: Router(config)# aaa server radius dynamic-author	Configures a device as an Authentication, Authorization, and Accounting (AAA) server to facilitate interaction with an external policy server and enters dynamic authorization local server configuration mode. Note    This is an optional command if taps are always started with a session starts. The command is required if CoA-Requests are used to start and stop taps in existing sessions.
Step 11	client ip-address Example: Router(config-locsvr-da-radius)# client 10.0.0.2	(Optional) Specifies a RADIUS client from which the device will accept CoA-Request packets.
Step 12	domain {delimiter character| stripping [right-to-left]} Example: Router(config-locsvr-da-radius)# domain stripping right-to-left Example: Router(config-locsvr-da-radius)# domain delimiter @	(Optional) Configures username domain options for the RADIUS application. The delimiter keyword specifies the domain delimiter. One of the following options can be specified for the character argument: @, /, $, %, \, # or - The stripping keyword compares the incoming username with the names oriented to the left of the @ domain delimiter. The right-to-left keyword terminates the string at the first delimiter going from right to left.
Step 13	server-key word Example: Router(config-locsvr-da-radius)# server-key samplekey	(Optional) Configures the RADIUS key to be shared between a device and RADIUS clients.
Step 14	port port-number Example: Router(config-locsvr-da-radius)# port 1600	(Optional) Specifies a RADIUS client from which the device will accept CoA-Request packets.
Step 15	exit Example: Router(config-locsvr-da-radius)# exit	Exits dynamic authorization local server configuration mode and returns to global configuration mode.
Step 16	end Example: Router(config)# end	Exits the current configuration mode and returns to privileged EXEC mode.