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Versions: 00 01 02 RFC 3924

Internet Engineering Task Force                          Fred Baker
Internet Draft                                          Bill Foster
Document: <draft-baker-slem-architecture-02.txt>         Chip Sharp
Category: Informational                                October 2003

         Cisco Architecture for Lawful Intercept In IP Networks

Status of this Document

  This document is an Internet-Draft and is in full conformance with
  all provisions of Section 10 of RFC2026

  Internet-Drafts are working documents of the Internet Engineering
  Task Force (IETF), its areas, and its working groups. Note that other
  groups may also distribute working documents as Internet- Drafts.

  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time. It is inappropriate to use Internet- Drafts as reference
  material or to cite them other than as "work in progress."

  The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at


  For the purposes of this document, lawful intercept is the lawfully
  authorized interception and monitoring of communications. Service
  providers are being asked to meet legal and regulatory requirements
  for the interception of voice as well as data communications in IP
  networks in a variety of countries worldwide. Although requirements
  vary from country to country, some requirements remain common even
  though details such as delivery formats may differ. This document
  describes Cisco's Architecture for supporting lawful intercept in IP
  networks. It provides a general solution that has a minimum set of
  common interfaces.  This document does not attempt to address any of
  the specific legal requirements or obligations that may exist in a
  particular country.

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                            Table of Contents

1. Introduction.......................................................2
 1.1. Requirements Motivating the Architecture........................3
 1.2. Document Organization...........................................4
2.0. Reference Model..................................................5
 2.1. Reference Model Components......................................6
 2.2. Operational Considerations......................................7
3.0. Interfaces.......................................................9
 3.1. Content Intercept Request Interface.............................9
 3.2. Intercept Content Interface (f)................................10
 4.1. Voice over IP networks.........................................10
   4.1.1. Interception of Voice over IP Services.....................10
   4.1.2. Local Voice Services.......................................11
 4.2. Data Services..................................................12
5.0. Security Considerations.........................................13
 5.1. Content Request Interface (d) - SNMPv3 Control.................13
6.0. References......................................................14
7.0. Acronyms........................................................15
8.0. Authors' Addresses..............................................15

1. Introduction

  For the purposes of this document, lawful intercept is the lawfully
  authorized interception and monitoring of communications of an
  intercept subject. The term "intercept subject", "subject", "target
  subscriber" or "target" in this document refers to the subscriber of
  a telecommunications service whose communications and/or intercept
  related information (IRI) has been lawfully authorized to be
  intercepted and delivered to some agency. Note that although the term
  "Law Enforcement Agency" (LEA) is used throughout this document, this
  may refer to any agency that is able to request lawfully authorized

  By intercept related information (IRI) we mean information related to
  the IP traffic of interest.  There is currently no standardized
  definition for IRI for IP traffic.  IRI has been defined for a few
  services that might run over IP (e.g., Voice over IP) or that IP runs
  on top of (e.g., GPRS).  For example, IRI for voice over IP could be
  the called and calling phone numbers. The definition of IRI from [14]
  is shown below:

               Intercept Related Information: collection of
               information or data associated with
               telecommunication services involving the target

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               identity, specifically communication associated
               information or data (e.g. unsuccessful
               communication attempts), service associated
               information or data (e.g. service profile
               management by subscriber) and location

  Service providers are being asked to meet legal and regulatory
  requirements for the interception voice as well as data
  communications in IP networks in a variety of countries worldwide.
  Although requirements vary from country to country, some requirements
  remain common even though details such as delivery formats may
  differ. This document describes Cisco's Architecture for supporting
  lawful intercept in IP networks. It provides a general solution that
  has a minimum set of common interfaces. This document does not deal
  with legal requirements or obligations.

  This document describes one method for supporting lawful intercept.
  Other methods may be available.

1.1. Requirements Motivating the Architecture

  The purpose of the following list of requirements is to provide an
  understanding of the motivation behind the architecture and some of
  the requirements imposed on components and interfaces that are
  described in the later sections of the document. This does not imply
  any legal requirements on service providers or equipment vendors
  although such requirements may coincide.

  Note that there are a variety of requirements that have been defined
  for lawfully authorized intercept throughout the world. Some of these
  have been defined by standards bodies (e.g. [13]), while others are
  country specific. The following itemized list is a distillation of
  some of these, although a given item may or may not apply to a
  specific country:

     * Lawful Intercept (LI) should be undetectable by the intercept

     * Mechanisms should be in place to limit unauthorized personnel
       from performing or knowing about lawfully authorized intercepts.

     * There is often a requirement (especially for telecommunications
       services) to provide intercept related information (IRI)
       separately from the actual Internet Protocol (IP) traffic (or
       content) of interest (Note: some authorizations may be
       restricted to IRI).

     * If IRI is delivered separately from content, there should be
       some means to correlate the IRI and the content with each other.

     * If the information being intercepted is encrypted by the service
       provider and the service provider has access to the keys, then
       the information should be decrypted before delivery to the Law

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       Enforcement Agency (LEA) or the encryption keys should be passed
       to the Law Enforcement Agency to allow them to decrypt the

     * If the information being intercepted is encrypted by the
       intercept subject and its associate and the service provider has
       access to the keys, then the service provider may deliver the
       keys to the LEA.

     * There is often a requirement for a service provider to be able
       to do multiple simultaneous intercepts on a single subject.  The
       fact that there are multiple intercepts should be transparent to
       the LEAs.

     * There is often a requirement that the service provider should
       not deliver any unauthorized information to the LEA.

  The architecture and interfaces described in this document attempts
  to address these requirements.

1.2. Document Organization

  Section 1 of this document lists requirements motivating the
  architecture. Section 2 of this document describes a reference model
  along with some operation considerations. Section 3 provides more
  detailed requirements on the interfaces related to content
  interception. Section 4 applies the reference model to voice over IP
  and data intercepts and Section 5 examines security considerations.

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2.0. Reference Model

  This section describes a generic reference model (Figure 1) for
  lawful intercept.

                         +--------------------+               +-----+
                         |  LI Administration |     HI1(a)    |     |
                         |      Function      |<--------------|     |
                         +--------------------+               |     |
                                |                             |     |
                                | MD Provisioning             |     |
                                | Interface(b)                | LEA |
                                v                             |     |
  +-----------+           +--------------------+              |     |
  |           |<---(c)----|                    |              |     |
  |  IRI IAP  |--IRI(e)-->|      Mediation     |----HI2(g)--->|     |
  |           |           |      Device (MD)   |              |     |
  +-----------+           |                    |----HI3(h)--->|     |
                          +--------------------+              +-----+
                               |         ^
                     Intercept |         | Intercepted
                    Request(d) |         | Content(f)
                               |         |
                               v         |
                       User  |       Content      |  User
                     ------->|         IAP        |-------->
                     Content +--------------------+  Content

     Figure 1: Intercept Architecture

  A brief description of the interfaces is included in table 1 below.
  For a more detailed description of the interfaces refer to section 3.
  For a description of the components refer to section 2.1.

     Table 1 LI Interfaces

      Interface            Description
    ---------------------  -------------------------------------------
   (a) HI1                   Handover Interface 1 - Administration
                              Interface: The LEA provides intercept
                              information to the service provider
                              administration function.

   (b) MD Provisioning       Mediation Device provisioning interface.
                              Parameters include: target identifier,
                              duration of intercept, type of intercept,

   (c) IRI IAP Provisioning  Specifies Target identifier, duration,
                              etc. for provisioning of delivery of
                              Intercept Related Information (IRI).

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   (d) Content Intercept     Provisioning of the Content IAP.

   (e) IRI to MD             Internal interface between IRI Intercept
                             Access Point (IAP) and Mediation device
                             (MD) for delivery of IRI.

   (f) Content to MD         Internal interface between content
                             IAP and MD for delivery of Content.

   (g) HI2                   Handover Interface 2: Interface between
                              the MD and LEA for delivering IRI. This
                              interface may vary from country to

   (h) HI3                   Handover Interface 3: Interface between
                              the MD and LEA for delivering Content.
                              This interface may vary from country to

2.1. Reference Model Components

  A brief description of the key components in the reference model is
  as follows:

  Lawful Intercept (LI) Administration Function:
     This function provides the (typically manual) provisioning
     interface for the intercept as a result of a court order or
     warrant delivered by the Law Enforcement Agency (LEA). It could
     involve separate provisioning interfaces for several components,
     but more typically is a single interface to the Mediation Device
     (MD), which then takes care of provisioning of other components in
     the network. Because of the requirement in some laws to limit
     accessibility to authorized personnel, the provisioning interface
     has to be strictly controlled. In many cases, the identity of the
     subject received from the LEA has to be translated into an
     identity that can be used by the network to enable the intercept.

  Intercept Access Point (IAP):
     An IAP is a device within the network that is used for
     intercepting lawfully authorized intercept information. It may be
     an existing device that has intercept capability or it could be a
     special device that is provided for that purpose. Two types of
     IAP's are discussed here: IAP's that provide content; and IAP's
     that provide intercept related information (IRI).

  Content IAP:
     A content IAP is an IAP that is used to intercept the IP traffic
     of interest.

  IRI IAP: This is an IAP that is used to provide intercept related
  information (IRI).

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  Law Enforcement Agency (LEA):
     This is the agency that has requested the intercept and to which
     the service provider delivers the information.

  Mediation Device (MD):
     The MD requests intercepts from IAPs through interfaces (c) and
     (d) in Figure 1. The Mediation Device receives the data from the
     IAP, packages it in the correct format (which may vary from
     country to country) and delivers it to the LEA. In the case where
     multiple law enforcement agencies are intercepting the same
     subject, the mediation device may replicate the information
     multiple times. The assumption is that the service provider
     operates the MD (via specially authorized personnel) and that the
     LEA only has access to interfaces (a), (g) and (h) in Figure 1.

2.2. Operational Considerations

     In a typical operation, a lawfully authorized surveillance request
     arrives for a specified intercept subject. Authorized personnel
     provision the intercept using interface (b) in Figure 1, which may
     be for content only, IRI only or both. Once the intercept is
     provisioned, the IAP's send the IRI and/or content to the MD,
     which formats the information into the appropriate format for
     delivery to the LEA. Some operational issues that need to be

       * Location and Address Information for Content Intercepts: In
          some cases where the location and/or addressing information
          for the intercept is not known until the subject registers
          (or makes a call in the case of voice), the IRI may provide
          needed information in order to do the content tap (e.g. the
          IP address and port for the content streams).

       * Content Encryption: If the intercept content is encrypted and
          the service provider has access to the encryption keys (e.g.,
          receives keys in Session Description Protocol for Voice over
          IP), then the keys can be sent via IRI. It is, however,
          possible for end-users to exchange keys by some other means
          without any knowledge of the service provider in which case
          the service provider will not be able to provide the keys.
          Content transformations could make decryption at the LEA
          impossible. This is why the original packets are provided on
          interface (f) rather than attempting to convert them to some
          other format.

       * Detection by the Intercept Subject: One requirement is to
          ensure that the intercept subject is unable to detect that
          they are being intercepted. This document assumes a
          sophisticated subject:

            - Able to check IP addresses, use traceroute, etc.

            - Able to check if any unusual signaling is occurring on
               their customer premises equipment (CPE).

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            - Able to detect degradation or interruptions in service.

          This is why the intercept mechanism described here does not
          involve special requests to the CPE, re-routing of packets or
          end-to-end changes in IP addresses. Instead, content
          intercept is done on a device along the normal content path
          (i.e. no re-routing has occurred) that is within the service
          provider's network. A convenient content IAP is a router or
          switch at the edge of the service providerÂ’s network to which
          the intercept subject connects. This is illustrated in Figure

            Customer Premises  | Service Provider's Network
                +-----+             |       |
                | CPE |-------------| Router|----------
                +-----+             | (IAP) |
                                    |       |

                  Figure 2  Content IAP - Router

          Another possibility of course is to provide a special device
          along the path to provide the content IAP capabilities.

          Note that in the case where there is multi-homing (two or
          more routers connected to provide access for the CPE),
          intercept taps may have to be installed on more than one
          access router.  If the CPE is multi-homed to multiple service
          providers, then the intercept will have to be installed on
          each service provider separately and the LEA will have to
          correlate the data.

       * Unauthorized Creation and Detection: Another concern is the
          prevention of unauthorized creation and detection of
          intercepts. This is particularly important when a network
          element such as a router is used as a content IAP. Those
          routers that have the capability should be carefully
          controlled with access to intercept capability and
          information only via authorized personnel. In one approach
          using the reference model in Figure 1, the MD is in a
          controlled environment and the MD does the intercept request
          to the content IAP over an encrypted link.  Logging and
          auditing are used to detect unauthorized attempts to access
          the intercept capability.

       * Capacity:  Support for lawful intercept on a network element
          supporting customers consumes resources on that equipment.
          Therefore, support for lawful intercept requires capacity

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          planning and engineering to ensure that revenue-producing
          services are not adversely affected.

3.0. Interfaces

This section provides a brief description of the interfaces in the
reference model (Figure 1). A list of these interfaces is included in
Table 1 in Section 2.

  One of the objectives in defining these interfaces is to keep the
  internal interfaces (b to f) the same regardless of country-specific
  requirements. The MD then formats the IRI and the content to meet the
  country specific requirements for interfaces (g) and (h).

3.1. Content Intercept Request Interface

  This section describes some of the requirements for the content
  intercept request interface (d) in Figure 1. It makes use of a common
  request protocol (SNMPv3) regardless of the type of application (e.g.
  voice, data) and suggests the usage of a TAP-MIB, which is defined in
  a separate document [1]. Some of the considerations that lead to the
  use of SNMPv3 and to the definition of the specific Management
  Information Base (MIB) defined in [1] are provided here.

  In order to provide a generic interface for intercepting,
  replicating, encapsulating and transporting content packets to the
  MD, the content intercept interface ((d) in Figure 1) should specify:

     * A Filter specification for classifying the packets to be

     * The destination address of the MD (where to send the packets).

     * Encapsulation and Transport parameters.

  In addition, a timeout value for the intercept should also be
  specified. This defines a limited lifetime for the intercept so that
  failures will not result in intercepts remaining beyond their
  authorized lifetime. If a failure of the MD occurs such that it is
  not able to supply the refresh to the timeout, then the intercept
  will cease to exist after the timeout expires. Similarly, if the IAP
  re-boots, then the intercept will not survive the re-boot unless the
  IAP is capable of ascertaining that the intercept lifetime
  requirements will continue to be met.

  In order for this to work, it must be possible for the mediation
  device to realize that there is a failure in the IAP such that it
  must re-establish the intercept. This may be in the form of an audit
  (from the MD to the IAP), or in the form of a heartbeat mechanism in
  the content stream, or both.

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3.2. Intercept Content Interface (f)

  The encapsulation method should retain all of the information in the
  original packets (source and destination addresses as well as
  payload) and provide an identifier for correlating the packets with
  the IRI. One encapsulation that meets those requirements is described
  in Section 4 of [2].  For non-voice intercepts, the "Intercepted
  Information" field in Table 1 of [2] contains the original
  intercepted IP packet.

  Note, however, that the interface defined in [2] is based on UDP
  which is an unreliable and unordered transport protocol (i.e.,
  provides neither retransmission on detection of errors nor ordering
  of data).  If this transport is used, the underlying network (Layers
  1 -    - 3) should be engineered to meet the overall reliability
  requirements for delivery of content.

  If a more reliable transport protocol is required, then a mechanism
  that provides timely delivery as well as limits the burden (both
  processing and buffering) on the Content IAP should be used. One
  mechanism that meets these requirements is a NACK-oriented
  retransmission scheme based on [12].

  If [12] is used, the call content channel identifier may be placed in
  the SSRC field of the encapsulating RTP packet.  The payload type may
  be used to identify the type of packet encapsulated in RTP (e.g., IP,
  PPP, Ethernet MAC).  Note that usage of [12] is still under
  investigation and may need further specification.  Usage of [12] in
  the content IAP places more processing burden on the content IAP than
  a UDP-based intercept and can affect the capacity of the content IAP.

4.0. Applying the Reference Model

  This section applies the reference model to some example

4.1. Voice over IP networks

  This section will look at some of the issues surrounding interception
  of voice over IP calls, taking local voice services as a specific
  service example. The reference model from Figure 1 will be applied
  with the use of a common set of interfaces that are independent of
  the call signaling protocols in use.

4.1.1. Interception of Voice over IP Services

  There are a variety of architectures in use for voice over IP (e.g.,
  centralized versus distributed) as well as various protocols (SIP
  [6], H.323 [9], MGCP [7], H.248 [8]). There are also a variety of
  services that may be offered:

     * Local Voice Services (i.e. service to a user that has an IP
       phone or a phone connected to a gateway)

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     * Transit services

     * Long distance access services (e.g. calling/debit card).

  This document does not address any obligations that a service
  provider might or might not have to support intercepts. It simply
  describes how intercept might be done using the reference model in
  Figure 1.

  Note that in the case of services where the intercept subject
  accesses the network via a non-IP endpoint (e.g., TDM), the
  detectability issue is less acute (e.g. re-routing of packets to
  intercept them in a special device is a possible option), since the
  intercept subject does not have access to the IP addresses or to

  However, in the case of local services, this is a much more difficult
  problem. The intercept for a call originating and terminating on-net
  (i.e. a call that is voice over IP end-to-end) has to be intercepted
  along its normal route in order to be undetectable. In addition, the
  call-forwarding feature that is often provided as a local service
  feature makes interception even more difficult: If call forwarding is
  invoked, a call that was intended to terminate on the intercept
  subject may be forwarded anywhere in the network resulting in the
  media stream bypassing the original content IAP (since in voice over
  IP, the media stream goes directly from end-to-end). Also, since call
  forwarding can often be set up on a call-by-call basis, the location
  of the content IAP will often not be known until the call is set up.

4.1.2. Local Voice Services

  This sub-section will look at the specific case in which the
  intercept subject under surveillance is being provided with a local
  voice service by the same provider that also provides the network
  access (e.g., controls the edge router or switch). This is an
  important assumption, since in VoIP the entity providing call control
  (e.g., SIP server) can be totally separate from the entity providing
  network access (e.g., operates edge routers).

  Suppose that a subscriber that subscribes to a local (e.g.
  residential) voice service is a target for a lawfully authorized
  surveillance. Part of the system providing these services is a
  subscriber database that includes addressing information about the
  subscriber as well information on what features are in effect (e.g.
  call forwarding). Some call control entity (CCE) accesses that
  database in order to provide local services. For example, if the
  subject has call forwarding invoked, that fact (and where to forward
  the call) is indicated in the subscriber database. A call arriving at
  the CCE that "owns" that subscriber can then take the appropriate
  action (e.g. forward the call).

  The CCE that "owns" the target subscriber (which could be an H.323
  gatekeeper, a SIP proxy or a Media Gateway Controller) is provisioned
  with the intercept parameters (e.g. subject identification

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  information such as the telephone number and where to deliver the
  IRI). The provisioning of this CCE could be through interface (c) in
  Figure 1. The CCE in question is the IRI IAP and once provisioned, it
  passes the IRI to the MD. In the scenario being discussed, the CCE
  typically remains in the signaling path throughout the call, even in
  the call-forwarding case. Part of the IRI it passes to the MD is the
  media signaling information (i.e. SDP [11] or H.245 [10]), which
  includes endpoint IP address and port information for the media
  (content) streams. Armed with this media address information, the MD
  can determine the content IAP (e.g. [5]) and make the request via
  interface (d).  The request identifies the voice stream to be
  intercepted based on information received in the call signaling
  (i.e., IP addresses and UDP port numbers).

  Note that the content IAP in the case of voice over IP could be an
  edge router or a PSTN gateway (e.g. a call from the PSTN forwarded to
  the PSTN). SIP, H.323, MGCP or H.248 call signaling protocols could
  be used. However, the protocol (SNMPv3 [1]) used for interface (d),
  is not dependent on the type of call signaling protocol used; nor is
  the encapsulation format and transport protocol (interface "f"). The
  same reference model (Figure 1) with the same interfaces can be used
  for lawfully authorized surveillance, regardless of the signaling
  protocol and regardless of the type of service being provided (Note:
  even though a local voice service was used in this example, other
  voice services could use the same model and interfaces).

4.2. Data Services

  The same model (Figure 1) can also be used for data services. In this
  case the IRI IAP could be a server that acts as registration,
  authentication and authorization point for the data service (e.g. a
  RADIUS server). If a potential IRI IAP does not have the available
  interfaces (c) and (e), the MD may have to do a content tap on
  registration signaling in order to obtain the IRI.

  The IRI in the case of a data service could include:

     * The time that the user registered or de-registered for the
     * Addressing information (i.e. given the user identity, what IP
       address or other information is available that could be used in
       interface (d) to do the content tap).

  Once suitable addressing information is available in order to do
  content tapping the MD can invoke the tap via interface (d).

  Clearly the IRI interfaces (c, e, g) are different for data than they
  are for voice services. However, the content IAP is typically the
  same (an edge router). Interfaces (d, f, and h) may also be the same.

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5.0. Security Considerations

  Given the sensitive nature of lawful intercept (LI) -- both from the
  standpoint of the need to protect sensitive data, as well as conceal
  the identities of the intercept subjects, the LI solution should have
  the ability to provide stringent security measures to combat threats
  such as impersonation of MD's, privacy and confidentiality breaches,
  as well as message forgery and replay attacks.

  While this document doesnÂ’t discuss issues of physical security,
  operating system, or application hardening within the principals of
  the LI solution, they are clearly important. In particular, the MD
  server would be considered a prime target for attacks.

  In general, all interfaces should have the capability of providing
  strong cryptographic authentication to establish the identity of the
  principals, and be able to correlate the identity of the principal
  with the action they are attempting to perform. All interfaces should
  be capable of performing some sort of cryptographic message integrity
  checking such as, for example, HMAC-MD5. Message integrity checking
  can also be used to counter replay attacks. Privacy and
  confidentiality considerations, may also require the use of

  The content and IRI IAPs also should also provide protection of the
  identity of the intercept subject and the existence of an intercept.

5.1. Content Request Interface (d) - SNMPv3 Control

  For interface (d,) native SNMPv3 security module mechanism is used.
  The additional requirement is that the IAP should support the ability
  to protect the TAP MIB's [1] from disclosure or control by
  unauthorized USM [3] users. VACM [4] provides the necessary tools to
  limit the views to particular USM users, but there are also special

     * The ability to limit access to the appropriate TAP MIB's by only
       those SNMPv3 USM users which have keys established and the
       proper VACM views defined.

     * Segregation of the TAP MIB such that only operators of
       sufficient privilege level can create VACM views that include
       the TAP MIB [1].

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6.0. References

     [1]  F. Baker, Cisco Lawful Intercept Control MIB, draft-baker-
       slem-mib-00, (work in progress)
     [2]  PacketCable(TM) Electronic Surveillance Specification, PKT-
       SP-ESP-I01-991229, http://www.packetcable.com/specifications/
     [3]  Blumenthal, U. and B. Wijnen, User-based Security Model(USM)
       for version 3 of the Simple Network Management Protocol
       (SNMPv3), STD 62, RFC3414, December 2002.
     [4]  B. Wijnen, et al, View-based Access Control Model (VACM) for
       the Simple Network Management Protocol (SNMP), STD62, RFC3415
       December 2002
     [5]  E. Warnicke, DNS Resolution of Networks and Gateways, IETF
       Draft draft-warnicke-network-dns-resolution-02.txt (work in
     [6]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
       Peterson, J., Sparks, R., Handley, M. and E. Schooler, SIP:
       Session Initiation Protocol, RFC3261, June 2002.
     [7]  F. Andreasen, B. Foster, Media Gateway Control Protocol
       (MGCP) Version 1.0, RFC3435, January 2003
     [8]  ITU-T Recommendation H.248.1, Gateway Control Protocol:
       Version 2, May 2002
     [9]  ITU-T Recommendation H.323, Packet-based Multimedia
       Communications Systems, November 2000
     [10] ITU-T Recommendation H.245, Control Protocol for Multimedia
       Communications, February 2003
     [11] M. Handley, V, Jacobson, SDP: Session Description Protocol,
       RFC2327 April 1998
     [12] J. Rey, D. Leon, A. Miyazaki, V. Varsa, R. Hakenber, RTP
       Retransmission Payload Format, draft-ietf-avt-rtp-
       retransmission-09.txt (work in progress)
     [13] ETSI TS 101 331, Telecommunications security; Lawful
       Interception (LI); Requirements of law enforcement agencies.
     [14] ETSI TS 33.108 v1.0.0, 3rd Generation Partnership Project;
       Technical Specification Group Services and System Aspects; 3G
       Security; Handover Interface for Lawful Interception.

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                   Architecture for Lawful Intercept       October 2003

7.0. Acronyms

CCE            Call Control Entity
CMTS           Cable Modem Termination System
CPE            Customer Premises Equipment
ETSI           European Telecommunications Standards Institute
GPRS           Generalized Packet Radio Service
HMAC-MD5       Hash-based Message Authentication Code -                                                      -
               Message Digest 5
IAP            Intercept Access Point
IETF           Internet Engineering Task Force
IRI            Intercept Related Information
ITU-T          International Telecommunications Union -                                                      -
               Telecommunications Sector
LEA            Law Enforcement Agency
LI             Lawful Intercept
MGCP           Media Gateway Control Protocol
MD             Mediation Device
MIB            Management Information Base
NACK           Negative Acknowledgement
PSTN           Public Switched Telecommunications Network
RFC            Request for Comment
RTP            Real-time Transport Protocol
SDP            Session Description Protocol
SIP            Session Initiation Protocol
SSRC           Synchronization Source
TDM            Time Division Protocol
UDP            User Datagram Protocol
USM            User Service Model
VACM           View-based Access Control Model
VoIP           Voice over IP

8.0. Authors' Addresses

     Fred Baker
     Cisco Systems
     1121 Via Del Rey
     Santa Barbara, CA  93117

     Phone: +1-408-526-4257
     Fax:   +1-413-473-2403
     EMail: fred@cisco.com

     Bill Foster
     Cisco Systems
     Email: bfoster@cisco.com

     Chip Sharp
     Cisco Systems
     Email: chsharp@cisco.com

Baker et al                  Informational                    [Page 15]

                   Architecture for Lawful Intercept       October 2003

  9.0. Full Copyright Statement

  Copyright (C) The Internet Society (2003).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published
  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph are
  included on all such copies and derivative works.  However, this
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
  copyrights defined in the Internet Standards process must be
  followed, or as required to translate it into languages other than

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assigns.

  This document and the information contained herein is provided on an


  Funding for the RFC Editor function is currently provided by the
  Internet Society.

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