Internet Engineering Task Force H.Cruickshank
Internet Draft S. Iyengar
draft-cruickshank-ipdvb-sec-req-03.txt University of Surrey, UK
L. Duquerroy
Alcatel Alenia Space, France
Expires: February 4, 2007 P. Pillai
University of Bradford, UK
Category: Internet Draft August 4, 2006
Security requirements for the Unidirectional Lightweight
Encapsulation (ULE) protocol
draft-cruickshank-ipdvb-sec-req-03.txt
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Abstract
This document provides a threat analysis and derives security
requirements for MPEG-2 transmission links using the
Unidirectional Lightweight Encapsulation (ULE). It also provides
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the motivation for ULE link-level security. This work is intended
as a work item of the ipdvb WG, and contributions are sought from
the IETF on this topic.
Table of Contents
1. Introduction..............................................2
2. Requirements notation.....................................4
3. Threat Analysis...........................................6
3.1. System Components....................................6
3.2. Threats..............................................7
3.3. Threat Scenarios.....................................8
4. Security Requirements for IP over MPEG-2 TS...............9
5. IPsec and MPEG-2 Transmission Networks....................10
6. Motivation for ULE link-layer security....................11
6.1. Link security below the Encapsulation layer..........11
6.2. Link security as a part of the Encapsulation layer...12
7. Summary...................................................13
8. Security Considerations...................................13
9. IANA Considerations.......................................14
10. Acknowledgments..........................................14
11. References...............................................14
11.1. Normative References................................14
11.2. Informative References..............................14
Author's Addresses...........................................16
Intellectual Property Statement..............................17
Disclaimer of Validity.......................................17
Copyright Statement..........................................17
1. Introduction
The MPEG-2 Transport Stream (TS) has been widely accepted not
only for providing digital TV services, but also as a subnetwork
technology for building IP networks. RFC 4326 [RFC4326] describes
the Unidirectional Lightweight Encapsulation (ULE) mechanism for
the transport of IPv4 and IPv6 Datagrams and other network
protocol packets directly over the ISO MPEG-2 Transport Stream as
TS Private Data. ULE specifies a base encapsulation format and
supports an extension format that allows it to carry additional
header information to assist in network/Receiver processing. The
encapsulation satisfies the design and architectural requirement
for a lightweight encapsulation defined in RFC 4259 [RFC4259].
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Section 3.1 of RFC 4259 presents several topological scenarios
for MPEG-2 Transmission Networks. A summary of these scenarios
are presented below (for full detail, please refer to RFC 4259).
1. Broadcast TV and Radio Delivery.
2. Broadcast Networks used as an ISP. This resembles to scenario
1, but includes the provision of IP services providing access
to the public Internet.
3. Unidirectional Star IP Scenario. It utilizes a Hub station to
provide a data network delivering a common bit stream to
typically medium-sized groups of Receivers.
4. Datacast Overlay. It employs MPEG-2 physical and link layers
to provide additional connectivity such as unidirectional
multicast to supplement an existing IP-based Internet service.
5. Point-to-Point Links.
6. Two-Way IP Networks. This can be typically satellite-based and
star-based utilising a Hub station to deliver a common bit
stream to medium- sized groups of receivers. A bidirectional
service is provided over a common air-interface.
RFC 4259 states that ULE must be robust to errors and security
threats. Security must also consider both unidirectional as well
as bidirectional links for the scenarios mentioned above.
An initial analysis of the security requirements in MPEG-2
transmission networks is presented in the security considerations
section of RFC 4259. For example, when such networks are not
using a wireline network, the normal security issues relating to
the use of wireless links for transport of Internet traffic
should be considered [RFC3819].
The security considerations of RFC 4259 recommends that any new
encapsulation defined by the IETF should allow Transport Stream
encryption and should also support optional link-level
authentication of the SNDU payload. In ULE [RFC4326], it is
suggested that this may be provided in a flexible way using
Extension Headers. This requires the definition of a mandatory
header extension, but has the advantage that it decouples
specification of the security functions from the encapsulation
functions.
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This document extends the above analysis and derives a detailed
the security requirements for ULE in MPEG-2 transmission
networks.
2. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC2119 [RFC2119].
Other terms used in this document are defined below:
ATSC: Advanced Television Systems Committee. A framework
and a set of associated standards for the transmission of video,
audio, and data using the ISO MPEG-2 standard.
DVB: Digital Video Broadcast. A framework and set of associated
standards published by the European Telecommunications Standards
Institute (ETSI) for the transmission of video, audio, and data
using the ISO MPEG-2 Standard [ISO-MPEG2].
Encapsulator: A network device that receives PDUs and formats
these into Payload Units (known here as SNDUs) for output as a
stream of TS Packets.
LLC: Logical Link Control [ISO-8802-2, IEEE-802.2]. A link-layer
protocol defined by the IEEE 802 standard, which follows the
Ethernet Medium Access Control Header.
MAC: Message Authentication Code.
MPE: Multiprotocol Encapsulation [ETSI-DAT]. A scheme that
encapsulates PDUs, forming a DSM-CC Table Section. Each Section
is sent in a series of TS Packets using a single TS Logical
Channel.
MPEG-2: A set of standards specified by the Motion Picture
Experts Group (MPEG) and standardized by the International
Standards Organisation (ISO/IEC 13818-1) [ISO-MPEG2], and ITU-T
(in H.222 [ITU-H222]).
NPA: Network Point of Attachment. In this document, refers to a
6-byte destination address (resembling an IEEE Medium Access
Control address) within the MPEG-2 transmission network that is
used to identify individual Receivers or groups of Receivers.
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PDU: Protocol Data Unit. Examples of a PDU include Ethernet
frames, IPv4 or IPv6 datagrams, and other network packets.
PID: Packet Identifier [ISO-MPEG2]. A 13-bit field carried in
the header of TS Packets. This is used to identify the TS
Logical Channel to which a TS Packet belongs [ISO-MPEG2]. The TS
Packets forming the parts of a Table Section, PES, or other
Payload Unit must all carry the same PID value. The all-zeros
PID 0x0000 as well as other PID values are reserved for specific
PSI/SI Tables [ISO-MPEG2]. The all-ones PID value 0x1FFF
indicates a Null TS Packet introduced to maintain a constant bit
rate of a TS Multiplex. There is no required relationship
between the PID values used for TS Logical Channels transmitted
using different TS Multiplexes.
Receiver: Equipment that processes the signal from a TS Multiplex
and performs filtering and forwarding of encapsulated PDUs to the
network-layer service (or bridging module when operating at the
link layer).
SI Table: Service Information Table [ISO-MPEG2]. In this
document, this term describes a table that is defined by another
standards body to convey information about the services carried
in a TS Multiplex. A Table may consist of one or more Table
Sections; however, all sections of a particular SI Table must be
carried over a single TS Logical Channel [ISO-MPEG2].
SNDU: SubNetwork Data Unit. An encapsulated PDU sent as an MPEG-2
Payload Unit.
TS: Transport Stream [ISO-MPEG2], a method of transmission at the
MPEG-2 level using TS Packets; it represents layer 2 of the
ISO/OSI reference model. See also TS Logical Channel and TS
Multiplex.
TS Multiplex: In this document, this term defines a set of MPEG-2
TS Logical Channels sent over a single lower-layer connection.
This may be a common physical link (i.e., a transmission at a
specified symbol rate, FEC setting, and transmission frequency)
or an encapsulation provided by another protocol layer (e.g.,
Ethernet, or RTP over IP). The same TS Logical Channel may be
repeated over more than one TS Multiplex (possibly associated
with a different PID value) [RFC4259]; for example, to
redistribute the same multicast content to two terrestrial TV
transmission cells.
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TS Packet: A fixed-length 188B unit of data sent over a TS
Multiplex [ISO-MPEG2]. Each TS Packet carries a 4B header, plus
optional overhead including an Adaptation Field, encryption
details, and time stamp information to synchronise a set of
related TS Logical Channels.
3. Threat Analysis
3.1. System Components
+------------+ +------------+
| IP | | IP |
| End Host | | End Host |
+-----+------+ +------------+
| ^
+------------>+---------------+ |
+ IP | |
+-------------+ Encapsulator | |
SI-Data | +------+--------+ |
+-------+-------+ |MPEG-2 TS Logical Channel |
| MPEG-2 | | |
| SI Tables | | |
+-------+-------+ ->+------+--------+ |
| -->| MPEG-2 | . . .
+------------>+ Multiplexor | |
MPEG-2 TS +------+--------+ |
Logical Channel |MPEG-2 TS Mux |
| |
Other ->+------+--------+ |
MPEG-2 -->+ MPEG-2 | |
TS --->+ Multiplexor | |
---->+------+--------+ |
|MPEG-2 TS Mux |
| |
+------+--------+ +------+-----+
|Physical Layer | | MPEG-2 |
|Modulator +---------->+ Receiver |
+---------------+ MPEG-2 +------------+
TS Mux
Figure 1: An example configuration for a unidirectional Service
for IP transport over MPEG-2 [RFC4259].
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As shown in Figure 1 (in section 3.3 of [RFC4259]), there
are several entities within the MPEG-2 transmission network
architecture. These include:
o ULE Encapsulation Gateways (or Encapsulator or ULE source)
o SI-Table signalling generator (input to the multiplexor)
o Receivers
o TS multiplexers (including re-multiplexers)
o Modulators
In an MPEG-2 network a set of signalling messages [ID-AR] may
need to be broadcast (e.g. by an Encapsulation Gateway)
or other device to form the L2 control plane. Examples of
signalling messages include the Program Association Table
(PAT), Program Map Table (PMT) and Network Information Table
(NIT). In existing MPEG-2 transmission networks, these messages
are broadcasted in the clear (no encryption or integrity checks).
he integrity of these messages is important for correct working
of the ULE network. However, securing these messages is out of
scope for ULE security, because these messages are not normally
encapsulated with the ULE method.
ULE link security focuses only on the security between the ULE
Encapsulation Gateway (ULE source) and the Receiver. Securing
the ULE source and receivers eliminates the need to consider
security issues regarding the remaining system components,
such as multiplexers, re-multiplexers and modulators.
3.2. Threats
The simplest type of network threat is a passive threat. It
includes eavesdropping or monitoring of transmissions, with a
goal to obtain information that is being transmitted. In
broadcast networks (especially those utilising widely available
low-cost physical layer interfaces, such as DVB) passive threats
are considered the major threats. An example of such a threat is
an intruder monitoring the MPEG-2 transmission broadcast and
then extracting traffic information concerning the communication
between IP hosts using a link. Another example is of an intruder
trying to gain information about the communication parties by
monitoring their ULE Receiver NPA addresses; an intruder can gain
information by determining the layer 2 identity of the
communicating parties and the volume of their traffic. This is a
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well-known issue in the security field; however it is more
problematic in the case of broadcast networks such as MPEG-2
transmission networks.
Active threats (or attacks) are, in general, more difficult to
implement successfully than passive threats, and usually require
more sophisticated resources and may require access to the
transmitter. Within the context of MPEG-2 transmission networks,
examples of active attacks are:
o Masquerading: An entity pretends to be a different entity.
This includes masquerading other users and subnetwork control
plane messages.
o Modification of messages in an unauthorised manner.
o Replay attacks: When an intruder sends some old (authentic)
messages to the Receiver. In the case of a broadcast link,
access to previous broadcast data is easy.
o Denial of Service attacks: When an entity fails to perform its
proper function or acts in a way that prevents other entities
from performing their proper functions.
The active threats mentioned above are major security concerns
for the Internet community. The defence against such attacks is
data integrity using cryptographic techniques and sequence
numbers [BELLOVIN].
3.3. Threat Scenarios
Analysing the topological scenarios for MPEG-2 Transmission
Networks in section 1, the security threat cases can be
abstracted into three cases:
o Case 1: Monitoring (passive threat). Here the intruder
monitors the ULE broadcasts to gain information about the
ULE data and/or tracking the communicating parties identities
(by monitoring the destination NPA). In this scenario,
measures must be taken to protect the ULE data and the
identity of ULE Receivers.
o Case 2: Local hijacking of the MPEG-TS multiplex (active
threat). Here an intruder is assumed to be sufficiently
sophisticated to over-ride the original transmission from
the ULE Encapsulation Gateway and deliver a modified version
of the MPEG-TS transmission to a single ULE Receiver or a
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small group of Receivers (e.g. in a single company site). The
MPEG transmission network operator might not be aware of such
attacks. Measures must be taken to ensure ULE source
authentication and preventing replay of old messages.
o Case 3: Global hijacking of the MPEG-TS multiplex (active
threat). Here we assume an intruder is very sophisticated and
able to hijack the whole MPEG transmission multiplex. The
requirements here are similar to scenario 2. The MPEG
transmission network operator can usually identify such
attacks and may resort to some means to restore the original
transmission.
In terms of priority, case 1 is considered the major threat in
MPEG transmission systems. Case 2 is likely to a lesser degree
within certain network configurations. Hence, protection against
such active actives should be used only when such a threat is a
real possibility. Case 3 is envisaged to be less practical,
because it will be very difficult to pass unnoticed by the MPEG
transmission operator. It will require restoration of the
original transmission. Therefore case 3 is not considered further
in this document.
4. Security Requirements for IP over MPEG-2 TS
From the threat analysis in section 2, the following security
requirements can be derived:
o Data confidentiality is the major requirement to mitigate
passive threats in MPEG-2 broadcast networks.
o Protection of Layer 2 NPA address. In broadcast networks
this can be used to prevent an intruder tracking the
identity of ULE Receivers and the volume of their traffic.
o ULE source authentication is required against active attacks
described in section 2.2.
o Protection against replay attacks. This is required for
the active attacks described in section 2.2.
o Layer L2 ULE Receiver authorisation: This is normally
performed during the initial key exchange and authorisation
phase, before the ULE Receiver can join a secure session with
the ULE Encapsulator (ULE source).
Other general requirements are:
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o Decoupling of ULE key management functions from ULE security
services such as encryption and source authentication. This
allows the independent development of both systems.
o Traceability: To monitor transmission network using log files
to record the activities in the network and detect any
intrusion.
o Integrity of control and management messages in MPEG-2
transmission networks such as the SI tables (Figure 1).
o Compatibility with other networking functions such as NAT
Network Address Translation (NAT) [RFC3715] or TCP
acceleration can be used in a wireless broadcast networks.
Examining the threat cases in section 2.3, the security
requirements for each case can be summarised as:
o Case 1: Data confidentiality MUST be provided to prevent
monitoring of the ULE data (such as user information and IP
addresses). Protection of the NPA addresses MUST be provided
to prevent tracking ULE Receivers and their communications.
o Case 2: In addition to case 1 requirements, new measures need
to be implemented such as source authentication using Message
Authentication Code or TESLA [RFC4082] and using sequence
numbers to prevent replay attacks. This will significantly
reduce the ability of intruders to inject their own data
into the MPEG-TS stream. However, scenario 2 threats apply
only in specific service cases and therefore source
authentication and protection against replay attacks are
OPTIONAL. Such measures incur extra link transmission and
processing overheads.
o Case 3: The requirements here are similar to Case 2. In
addition, intrusion detection is also desirable by the MPEG-2
network operator.
5. IPsec and MPEG-2 Transmission Networks
The security architecture for the Internet Protocol [RFC4301]
describes security services for traffic at the IP layer. This
architecture primarily defines services for Internet Protocol
(IP) unicast packets, as well as manually configured IP multicast
packets. It is possible to use IPsec to secure ULE links. The
major advantage of IPsec is its wide implementation in IP routers
and hosts. IPsec in transport mode can be used for end-to-end
security transparently over MPEG-2 transmission links with little
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impact.
In the context of MPEG-2 transmission links, if IPsec is used to
secure a ULE link, then the ULE Encapsulator and Receivers are
equivalent to the security gateways in IPsec terminology. A
security gateway implementation of IPsec uses tunnel mode.
Such usage has the following disadvantages:
o There is an extra overheads associated with using IPsec in
tunnel mode, i.e. the extra IP header (IPv4 or IPv6).
o There is a need to protect the identity (NPA) of ULE Receivers
over the ULE broadcast medium; IPsec is not suitable for
providing this service. In addition, the interfaces of these
devices do not necessarily have IP addresses (they can be
L2 devices).
o Multicast is considered a major service over ULE links. The
current IPsec specifications [RFC4301] only define a pairwise
tunnel between two IPsec devices with manual keying. Work is
in progress in defining the extra detail needed for multicast
and to use the tunnel mode with address preservation to allow
efficient multicasting. For further details refer to [WEIS06].
6. Motivation for ULE link-layer security
Examination of the threat analysis and security requirements in
sections 3 and 4 has shown that there is a need to provide link-
layer (L2) security in MPEG-2 transmission networks employing
ULE.
ULE link security (between a ULE Encapsulation Gateway and
Receivers) is therefore considered an additional security
mechanism to IPsec, TLS, and application layer security, not a
replacement. It allows a network operator to provide
similar functions to that of IPsec [RFC4301], but in addition
provides MPEG-2 transmission link confidentiality and protection
of ULE Receiver identity (NPA).
A modular design to ULE Security may allow it to use and benefit
from IETF key management protocols, such as the Multicast
Security group (MSEC) GSAKMP [RFC4535] and GDOI [RFC3547]
protocols. This does not preclude the use of other key management
methods in scenarios where this is more appropriate.
6.1. Link security below the Encapsulation layer
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Link-layer security can be provided at the MPEG-TS level (below
ULE). MPEG-TS encryption encrypts all TS Packets sent with a
specific PID value. However, MPEG-TS may typically multiplex
several IP flows, belonging to different users, using a common
PID. Therefore all multiplexed traffic will share the same
security keys.
This has the following advantages:
o The bit stream sent on the broadcast network does not expose
any L2 or L3 headers, specifically all addresses, type fields,
and length fields are encrypted prior to transmission.
o This method does not preclude the use of IPsec, or any other
form of higher-layer security.
However it has the following disadvantages:
o Each ULE Receiver needs to decrypt all MPEG-2 TS Packets with
a matching PID, possibly including those that are not required
to be forwarded. Therefore it does not have the flexibility to
separately secure individual IP flows.
o ULE Receivers will have access to private traffic destined to
other ULE Receivers, since they share a common PID and key.
o Encryption of the MPE MAC address is not permitted in such
systems.
o IETF-based key management are not used in existing systems.
Existing access control mechanisms have limited flexibility in
terms of controlling the use of key and rekeying. Therefore if
the key is compromised, then this will impact several ULE
Receivers.
In practice, there are few L2 security solutions for MPEG
transmission networks. Conditional access for digital TV
broadcasting is one example. However, this approach is
optimised for TV services and is not well-suited to IP packet
transmission. Some other systems are specified in standards such
MPE [ETSI-DAT], but there are currently no known implementations.
6.2. Link security as a part of the Encapsulation layer
Examining the threat analysis in section 2 has shown that
protection of ULE link from eavesdropping and ULE Receiver
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identity are major requirements. In the context of active threats
in MPEG-2 transmission networks, ULE source authentication is
required by the ULE Receivers. Attacks such as masquerading,
modification of messages and injecting IP packets are more
difficult, but possible as presented in threat cases 2 and 3 (see
section 2).
There several major advantages in using ULE link level security:
o The protection of the complete ULE Protocol Data Unit (PDU)
including IP addresses. The protection can be applied either
per IP flow or per Receiver NPA address.
o Ability to protect the identity of the Receiver within the
MPEG-2 transmission network.
o Efficient protection of IP multicast over ULE links.
o Transparency to the use of Network Address Translation (NATs)
[RFC3715] and TCP Performance Enhancing Proxies (PEP)
[RFC3135], which require the ability to inspect and modify the
packets sent over the ULE link.
This method does not preclude the use of IPsec at L3 (or TLS
[RFC4346] at L4). IPsec also provides a proven security
architecture defining key exchange mechanisms and the ability to
use a range of cryptographic algorithms.
7. Summary
This document analyses a set of threats and security
requirements. It also defines the requirements for ULE security
and states the motivation for link security as a part of the
Encapsulation layer. This includes a need to provide L2
encryption and ULE Receiver identity protection.
There is an addition need (optional) for L2 source authentication
and protection against insertion of other data into the ULE
stream (i.e. data integrity). This is optional because of the
associated overheads for the extra features and they are only
required for specific service cases.
8. Security Considerations
Link-level (L2) encryption of IP traffic is commonly used in
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broadcast/radio links to supplement End-to-End security (e.g.
provided by TLS [RFC4346], SSH [RFC4251], IPsec [RFC4301). A
common objective is to provide the same level of privacy as wired
links. An ISP or User may also wish to provide end-to-end
security services to the end-users (based on well-known
mechanisms such as IPsec or TLS).
This document provides a threat analysis and derives the security
requirements to provide optional link encryption and link-level
integrity / authentication of the SNDU payload.
9. IANA Considerations
This document does not define any protocol and does not require
any IANA assignments.
10. Acknowledgments
The authors acknowledge the help and advice from Gorry Fairhurst
(University of Aberdeen). The authors also acknowledge contributions
from Stephane Coombes (ESA) and Dr Y. Fu (University of Bradford).
11. References
11.1. Normative References
[ISO-MPEG2] "Information technology -- generic
coding of moving pictures and associated audio
information systems, Part I", ISO 13818-1,
International Standards Organisation (ISO), 2000.
[RFC2119] Bradner, S., "Key Words for Use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, 1997.
11.2. Informative References
[ID-AR] G. Fairhurst, M-J Montpetit "Address Resolution
Mechanisms for IP Datagrams over MPEG-2 Networks",
Work in Progress <draft-ietf-ipdvb-ar-xx.txt>.
[IEEE-802.2] "Local and metropolitan area networks-
Specific requirements Part 2: Logical Link Control",
IEEE 802.2, IEEE Computer Society,
(also ISO/IEC 8802-2), 1998.
[ISO-8802-2]ISO/IEC 8802.2, "Logical Link Control", International
Standards Organisation (ISO), 1998.
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[ITU-H222] H.222.0, "Information technology, Generic coding of
moving pictures and associated audio information
Systems", International Telecommunication Union,(ITU-
T), 1995.
[RFC4259] Montpetit, M.-J., Fairhurst, G., Clausen, H.,
Collini-Nocker, B., and H. Linder, "A Framework for
Transmission of IP Datagrams over MPEG-2 Networks",
IETF RFC 4259, November 2005.
[RFC4326] Fairhurst, G. and B. Collini-Nocker, "Unidirectional
Lightweight Encapsulation (ULE) for Transmission of
IP Datagrams over an MPEG-2 Transport Stream (TS)",
IETF RFC 4326, December 2005.
[ETSI-DAT] EN 301 192, "Digital Video Broadcasting (DVB); DVB
Specifications for Data Broadcasting", European
Telecommunications Standards Institute (ETSI).
[BELLOVIN] S., "Problem Area for the IP Security protocols",
Computer Communications Review 2:19, pp. 32-48, April
989. http://www.cs.columbia.edu/~smb/
[RFC4082] A. Perrig, D. Song, " Timed Efficient Stream Loss-
Tolerant Authentication (TESLA): Multicast Source
Authentication Transform Introduction", IETF RFC
4082, June 2005.
[RFC4535] H Harney, et al, "GSAKMP: Group Secure Association
Group Management Protocol", IETF RFc 4535, June 2006.
[RFC3547] M. Baugher, et al, "GDOI: The Group Domain of
Interpretation", IETF RFC 3547.
[WEIS06] Weis B., et al, "Multicast Extensions to the Security
Architecture for the Internet", <draft-ietf-msec-
ipsec-extensions-02.txt>, June 2006, IETF Work in
Progress.
[RFC3715] B. Aboba and W Dixson, "IPsec-Network Address
Translation (NAT) Compatibility Requirements" IETF
RFC 3715, March 2004.
[RFC4346] T. Dierks, E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", IETF RFC 4346, April
2006.
[RFC3135] J. Border, M. Kojo, eyt. al., "Performance Enhancing
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Proxies Intended to Mitigate Link-Related
Degradations", IETF RFC 3135, June 2001.
[RFC4301] Kent, S. and Seo K., "Security Architecture for the
Internet Protocol", IETF RFC 4301, December 2006.
[RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J.,
and L. Wood, "Advice for Internet Subnetwork
Designers", BCP 89, IETF RFC 3819, July 2004.
[RFC4251] T. Ylonen, C. Lonvick, Ed., "The Secure Shell (SSH)
Protocol Architecture", IETF RFC 4251, January 2006.
Author's Addresses
Haitham Cruickshank
Centre for Communications System Research (CCSR)
University of Surrey
Guildford, Surrey, GU2 7XH
UK
Email: h.cruickshank@surrey.ac.uk
Sunil Iyengar
Centre for Communications System Research (CCSR)
University of Surrey
Guildford, Surrey, GU2 7XH
UK
Email: S.Iyengar@surrey.ac.uk
Laurence Duquerroy
Research Department/Advanced Telecom Satellite Systems
Alcatel Space, Toulouse
France
E-Mail: Laurence.Duquerroy@space.alcatel.fr
Prashant Pillai
Mobile and Satellite Communications Research Centre
School of Engineering, Design and Technology
University of Bradford
Richmond Road, Bradford BD7 1DP
UK
Email: P.Pillai@bradford.ac.uk
Cruickshank Expires February 4, 2007 [Page 16]
Internet-Draft Security Requirements for ULE August 2006
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Cruickshank Expires February 4, 2007 [Page 17]