By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. This document may not be modified, and derivative works of it may not be created, except to publish it as an RFC and to translate it into languages other than English.
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 http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 10, 2008.
This document surveys existing protocols for the control of network address translators and firewalls. It includes standards-level protocols developed by the IETF and other standards organizations, as well as protocols designed by individuals.
2. Protocol Classification
4. NSIS - NAT/Firewall Signaling Layer Protocol
5. MIDCOM - Managed Objects for Middlebox Communication
6. SIMCO - NEC's Simple Middlebox Configuration Protocol
7. Diameter Gq', Rx+, Gx+
8. UPnP - Internet Gateway Device Standardized Device Control Protocol
9. NAT-PMP - NAT Port Mapping Protocol
10. STUN - Controlling NAT Bindings using STUN
11. RSIP - Realm-Specific IP
12. ALD - Application Listener Discovery for IPv6
13. NLS - Network Layer Signaling Transport Layer
14. AFWC - Authorized IP Firewall Control Application
15. Security Considerations
16. IANA Considerations
18. Informative References
§ Authors' Addresses
§ Intellectual Property and Copyright Statements
Network address translators (NATs) and firewalls - frequently referred to as "middleboxes" - are a subject of active discussion in the IETF and related development and standardization communities. These devices are not part of the traditional end-to-end Internet architecture, because they usually operate on transport- and higher-layer information inside the network, which is a layering violation in the original architecture, because operating on that information was the exclusive providence of the end-hosts.
However, in practice, NATs have turned out to be necessary to be able to mitigate the IPv4 address space limitations of many network domains. Similarly, because the networking software in many systems has turned out to contain security defects of different kinds, use of firewalls is common to protect the systems from attacks coming from the network. Another motivation for firewalls is to protect against the abuse of possibly scarce of expensive bandwidth, for example, unwanted traffic on wireless links.
A shared disadvantage of NATs and firewalls is that they often encode knowledge about a particular set of higher-layer protocols and applications in order to operate. This practice prevents new types of network protocols or applications from being deployed end-to-end, unless the middleboxes are upgraded or reconfigured as well. For example, a firewall is usually configured with a list of ports for a set of common network applications, preventing introduction of new applications. Furthermore, they commonly only support traditional transport protocols, such as TCP and UDP, preventing the use of other protocols, such as IPsec, IP tunneling, or other transport protocols. In addition, many NATs and firewalls maintain some state for each active transport-layer session that typically needs to be refreshed in constant intervals, and can be initiated only by certain hosts.
The IETF is currently developing recommendations for the operation of NATs in the BEHAVE working group. These recommendations provide guidelines for how NATs should translate a number of common protocols, including TCP [I‑D.ietf‑behave‑tcp] (Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. Srisuresh, “NAT Behavioral Requirements for TCP,” September 2008.), UDP [RFC4787] (Audet, F. and C. Jennings, “Network Address Translation (NAT) Behavioral Requirements for Unicast UDP,” January 2007.), ICMP [I‑D.ietf‑behave‑nat‑icmp] (Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, “NAT Behavioral Requirements for ICMP protocol,” January 2009.) and IP multicast [I‑D.ietf‑behave‑multicast] (Wing, D. and T. Eckert, “IP Multicast Requirements for a Network Address (and port) Translator (NAT),” November 2007.). Other organizations are developing similar guidelines. One example are Microsoft's requirements for the "Works with Windows Vista" and "Certified for Windows Vista" logo program [VISTALOGO] (Microsoft Corporation, “Windows Logo Program Device Requirements for Windows Vista Client and Windows Server code named 'Longhorn' (Version 3.09),” December 2006.) (see page 121 to page 132).
Even if these efforts result in more unified behavior of middleboxes, they will not necessarily overcome the above-mentioned limitations: different protocols and applications will still need to adapt to the behavior of NATs and firewalls. Commonly, new protocols must be encapsulated into UDP packets in order to pass through these devices. Although the UDP header and protocol logic are minimal and do not consume much network capacity, the use of UDP causes other problems, because it is not connection-oriented. Because there are no messages for connection establishment or connection tear-down in UDP, a stateful NAT or firewall needs to monitor ongoing UDP traffic between a source and destination, and in the absence of such traffic assumes that the session has ended, removing the related session state. In practice, the timers for state clean-up have turned out to be short (on the order of seconds), requiring the end hosts to transmit frequent and resource-consuming keep-alive messages to refresh the session state maintained at middleboxes.
A more advanced method to overcome the limitations caused by NATs or firewalls would be to allow end-hosts to signal their communication characteristics and profiles explicitly to the NATs and firewalls, or alternatively to allow these devices to signal their configuration information to the end-hosts. With such schemes, the number of state-refreshing keep-alives could be significantly reduced, and NATs and firewalls could be made directly aware of the communication characteristics of the end-hosts.
A number of existing protocols have been proposed for this purpose, and new proposals are being prepared. This document aims to support such efforts by surveying existing proposals and by discussing the the benefits and shortcomings of these schemes.
This section categorizes the proposals into clusters to illustrate the major design choices.
A reasonable classification of RSIP (Section 11 (RSIP - Realm-Specific IP)), ALD (Section 12 (ALD - Application Listener Discovery for IPv6)), SOCKS (Section 3 (SOCKS)) and AFWC (Section 14 (AFWC - Authorized IP Firewall Control Application)) is still pending.
The following document were (or are being) developed within the IETF:
These protocols were developed outside the IETF:
The following protocols are proposals by individuals:
The SOCKS Protocol Version 5 [RFC1928] (Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and L. Jones, “SOCKS Protocol Version 5,” March 1996.) defines a method for nodes located on an IP network (such as an Intranet with no routing to the Internet) to establish TCP sessions and exchange UDP datagrams with another IP network (usually the global Internet). To that end, a SOCKS server must be located on the boundary of both networks, and SOCKS clients must explicitly request the server to relay their communication sessions.
When a SOCKS client establishes a TCP session to the remote network, it first connects to the SOCKS server on a well-known TCP port, sending a connection request with optional authentication credentials. The request specifies in which direction the TCP session is to be established, i.e., whether the SOCKS server will act as the active or passive endpoint. The SOCKS server, if it accepts the request, informs the client of the external IP address and TCP port number that it will use. If the SOCKS server acts as the passive endpoint, it sends an additional response once the TCP three-way handshake is completed. The SOCKS server then forwards traffic between the internal and external TCP sessions, until either of them is terminated.
UDP sessions are also initially negotiated via a TCP session to the SOCKS server, in a similar manner. If successful, the client obtains the IP address and UDP port number of a UDP relay server. The relay forwards UDP datagrams between the local and remote networks. When sending a datagram, the client adds an additional, SOCKS-specific header, which carries the IP address or DNS name of the remote peer and the intended destination UDP port number of the datagram. The relay adds the same header when forwarding datagrams from the remote network back to the client.
The SOCKS protocol makes few assumptions about the network environment it operates in. In particular, there can be any number NAT/firewall devices between the client and the SOCKS server, and there need not be a router between the local and remote networks. It is assumed that the SOCKS server itself can freely exchange TCP and UDP packets with the remote network.
SOCKS supports both IPv4 and IPv6 as well as translation from one to the other. SOCKS only supports UDP and TCP as transport protocols. Conveyance of IP header parameters other than the IP addresses (such as IP options, hop limit, TOS field, etc.) are not defined. SOCKS cannot be used for generic server applications: only one passive TCP session per request is allowed.
The protocol is mature and implementations for clients and servers are widely available. SOCKS is supported in many FTP and HTTP clients. Applications must usually be modified to support SOCKS, but it is also possible to implement SOCKS transparently as a shim layer above the BSD socket API.
SOCKS requires manual configuration on the client. SOCKS server address and optional credentials must be explicitly provisioned.
NSIS uses a two-layer architecture with one lower-layer transport (NTLP) and multiple upper-layer application signaling protocols (NSLPs). This section first discusses the generic properties of the NTLP transport and then the specific characteristics of the NAT/Firewall signaling protocol built upon it.
GIST [I‑D.ietf‑nsis‑ntlp] (Schulzrinne, H. and M. Stiemerling, “GIST: General Internet Signalling Transport,” June 2009.) establishes NTLP "routing" state that allows signaling messages to be routed forwards and backwards along a path. GIST also provides two ways to send signaling messages:
An important part of GIST is its discovery mechanism. As an outcome of the discovery procedure the querying node learns the address of the responding node, its capability and establishes GIST routing state.
Once the next NSIS aware node is known, a messaging association can be established between these two nodes using C-mode. The same procedure is repeated again and again for the C-Mode until the last GIST node is reached.
The NAT/Firewall NSLP description [I‑D.ietf‑nsis‑nslp‑natfw] (Stiemerling, M., Tschofenig, H., Aoun, C., and E. Davies, “NAT/Firewall NSIS Signaling Layer Protocol (NSLP),” April 2010.) defines an NSIS Signaling Layer Protocol (NSLP) for configuration of network address translators and firewalls on top of GIST.
The NATFW NSLP uses GIST as a transport for its signaling messages. Objects about a created NAT binding, as well as lifetime and signaling information (such as protocol headers and error messages) are contained in a NATFW NSLP message itself. All other information about the flow identifier and the session identifier is carried in GIST. For communication security between neighboring NATFW NSLP nodes the usage of Transport Layer Security (TLS) is specified. The usage of an authorization token is possible [I‑D.manner‑nsis‑nslp‑auth] (Manner, J., Stiemerling, M., Tschofenig, H., and R. Bless, “Authorization for NSIS Signaling Layer Protocols,” July 2008.)
It is useful to distinguish between two signaling modes:
The first mode (CREATE) is the traditional way of creating a NAT binding by sending a message from the data sender along the path to the data receiver. Figure 1 (The NATFW NSLP CREATE Mode) shows a message exchange for this signaling mode.
The second mode (EXTERNAL) is used when a data receiver is behind a NAT and wants to establish a NAT binding to allow incoming data traffic. Figure 2 (The NATFW NSLP EXTERNAL Mode) shows this mode. It was necessary to introduce this mode, because of an end-to-end reachability problem. Furthermore, it provides a transition scenario where the data receiver behind a NAT or a firewall is able to configure their middlebox locally.
Private Address Public Address +----------+ Space +----------+ Space +----------+ | Data | | NAT | | Data | | Sender | | | | Receiver | +----------+ +----------+ +----------+ | | | | CREATE | CREATE | |----------------------------->+--------------------------->| | | | | RESPONSE | RESPONSE | |<-----------------------------+<---------------------------| | | | ============================================================> Direction of data traffic
| Figure 1: The NATFW NSLP CREATE Mode |
With the CREATE mode shown in Figure 1 (The NATFW NSLP CREATE Mode) the data sender (which happens to be the NSIS initiator in this case) sends a message to request a NAT binding to be created. The message is targeted to the data receiver, which returns a success or failure in the RESPONSE message. The data sender learns about the new NAT binding with information carried in the RESPONSE message.
Public Internet Private Address +----------+ +----------+ Space +----------+ | Data | | NAT | | Data | | Sender | | | | Receiver | +----------+ +----------+ +----------+ | | | | | EXTERNAL | | |<---------------------------| | | | | | RESPONSE | | |--------------------------->| | | | ============================================================> Direction of data traffic
| Figure 2: The NATFW NSLP EXTERNAL Mode |
With the EXTERNAL mode shown in Figure 2 (The NATFW NSLP EXTERNAL Mode) the data receiver behind a NAT creates a NAT binding. This allows data traffic from a node on the Internet to be received. Please note that the EXTERNAL message is sent in the opposite direction of the data traffic.
This section discusses the pros and cons of the protocol.
Is the protocol is restricted to certain applications or network environments?
The usage of the protocol is not restricted to a specific environment but to take advantage of its features it is necessary that Network Address Translators and firewalls implement this protocol.
Does it require additional infrastructure, lower-layer features or cooperation from other entities?
While the protocol supports a zero-configuration scheme so that it works in almost network topologies. The protocol works with multiple nested NATs and firewalls unless the data receiver is behind a complex network topology combined with routing asymmetry (without) state synchronization between the edge firewalls when the data sender does not support the protocol as well.
To make use of the security functionality and to perform meaningful authorization capabilities it is, however, necessary to have some form of security infrastructure in place. The protocol provides a very flexible security model with support in different security architectures.
Furthermore,for the EXTERNAL signal mode to work it is necessary that the edge firewall or edge NAT towards the public Internet terminates the signaling message exchange since the message might be targeted towards an address that does not exist.
Does it require modifications to applications?
The protocol can be used in a proxy mode where no end host support is necessary. In order to benefit best from the supported functionality is is advisable to make applications aware of the capability.
How mature is the specification? Has the protocol seen any use or deployment?
The specification is passed Working Group Last Call and several implementations (including open source implementations) exist. However, the protocol is not deployed yet.
How does the client discover the middlebox?
The middlebox discovery is accomplished as part of the functionality provided in GIST, namely specifically crafted packets that look like data packets are used. These discovery packets are marked with a router alert option and they are intercepted by firewalls and NATs along the path.
What kinds of "pinholes" does the protocol support?
The protocol supports a long range of pinholes. The complete list can be found in Section 184.108.40.206 of GIST.
What kinds of prior security arrangements does the protocol assume?
When client authentication is required then the credentials of a ciphersuite available for TLS need to be available to the end host. The security architecture builds on a hop-by-hop security architecture. Alternatively, the usage of an authorization token is possible. Authorization tokens can also be used in a non-hop-by-hop fashion.
The security architecture is meant to provide strong security protection rather than opportunistic security mechanisms. Further security mechanisms can be added without the need to re-define the protocol by plugging new security functionality into GIST or the NATFW NSLP and my making use of the initial capability exchange.
Does it work if routers (not supporting this protocol) somewhere drop packets with IP options?
GIST and the NATFW NSLP has problems if routers drop packets marked with the Router Alert option. It is, however, possible to extend GIST with a different path-coupled signaling procedure.
Does the protocol allow running a general-purpose server behind the NAT/firewall?
To be completed [RFC3303] (Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and A. Rayhan, “Middlebox communication architecture and framework,” August 2002.).
To be completed [RFC4540] (Stiemerling, M., Quittek, J., and C. Cadar, “NEC's Simple Middlebox Configuration (SIMCO) Protocol Version 3.0,” May 2006.).
To be completed [need reference].
The Internet Gateway Device (IGD) is an "edge" interconnection device between a residential Local Area Network (LAN) and a Wide Area Network (WAN), providing connectivity to the Internet for the networked devices in the residential network. The IGD could be physically implemented as a dedicated, standalone device or modeled as a set of Universal Plug-and-Play (UPnP) devices and services on a personal computer.
As an UPnP-based protocol, the IGD Standardized Device Control Protocol [UPNP] (UPnP Forum, “Internet Gateway Device (IGD) Standardized Device Control Protocol V 1.0,” November 2001.) inherits the features that the UPnP Device Architecture provides for support zero-configuration, "invisible" networking, and automatic discovery for a breadth of device categories. Any device can dynamically join a network, obtain an IP address, announce its name, convey its capabilities upon request, and learn about the presence and capabilities of other devices. Devices can disconnect from the network automatically without leaving any unwanted state information behind.
The IGD Standardized Device Control Protocol contains a set of devices and services that allow clients (in the UPnP context also called "Control Points") to control the initiation and termination of connections, monitor status and events of connections, or manage host configuration services, e.g., DHCP or Dynamic DNS. Among these services, the "WANIPConnection" service provides the functionality that allows the Control Points to manage the network address translation on the IGD device.
The IGD Standardized Device Control Protocol preserves the ability of non-UPnP devices to initiate and/or share Internet access.
The IGD Standardized Device Control Protocol is intended to be used in unmanaged network environments such as those found typically in residential networks. The residential network can have up to four segments, a limitation inherited from the UPnP Device Architecture, because the TTL value for the link-local multicast discovery messages is four.
By design, the protocol does permit the presence of several residential gateways in the same network and also permits residential gateways to have multiple connections to the Internet. In practice, a lack of routing mechanisms across multiple, simultaneously active WAN connections on multiple WAN interfaces and related issues caused by multiple, simultaneously active Internet Gateway devices (e.g., default gateway conflict resolution, load balancing or fail over) make scenarios other than that of a single Gateway Device with a single Internet connection difficult to support.
A residential gateway supporting the IGD Standardized Device Control Protocol is able to operate in two modes. In "routed mode", the gateway shares the routable WAN IP address with the control points on the LAN using NAT. In "bridged" mode, all Ethernet packets from devices on the LAN are bridged to the WAN. In scenarios where the IP address on the WAN interface is not routable, the device can be switched from routed to bridged mode, allowing both the discovery of IGD Standardized Device Control Protocol devices further along the path as well as the use of other NAT hole-punching protocols.
Applications that intend to create port mappings on a residential gateway supporting the IGD Standardized Device Control Protocol need to have embedded control point functionality, enabling them to create port mappings from TCP or UDP port on the external IPv4 address to the corresponding ports on the internal IPv4 addresses.
The protocol is implemented in more than 90% of the consumer routers, although the functionality might not be enabled by default.
The NAT Port Mapping Protocol [I‑D.cheshire‑nat‑pmp] (Cheshire, S., “NAT Port Mapping Protocol (NAT-PMP),” April 2008.) is a light-weight binary protocol running on top of UDP between client hosts and their IPv4 gateway. Clients can send requests to their first-hop gateway on a well-known UDP port, in order to determine whether NAT-PMP is supported. If that is the case, they will also learn the external IPv4 address of the gateway device.
If the gateway supports NAT-PMP, a host can assume that it is behind a NAT and start sending request for mapping of external TCP or UDP ports on the external IPv4 address. Mappings can be destroyed explicitly. They also automatically expire after a timeout that can be negotiated per mapping, unless refreshed.
Through the use of link-local multicast, the gateway can notify hosts if its external IP changes, and/or if it has rebooted. In the latter case, hosts are expected to recreate any mappings. This procedure attempts to protect against loss of state at the gateway.
NAT-PMP assumes that there is one and only one NAT along the path, which also has to be the first-hop gateway. A gateway must not enable NAT-PMP if it is does not perform address/port translation.
NAT-PMP is applicable to small, unmanaged, non-routed networks, connecting multiple hosts to the IPv4 Internet through a single public IPv4 address. It does not require any configuration. Support from the gateway can be auto-detected by clients, and the trust model is solely based on network attachment. There is no support for IPv6, nor is there support for transport protocols other than TCP or UDP. Nested NATs and non-NAT'ing firewalls are not supported.
NAT-PMP covers the same use cases as [UPNP] (UPnP Forum, “Internet Gateway Device (IGD) Standardized Device Control Protocol V 1.0,” November 2001.), although it is not as widely deployed today. (NAT-PMP is currently mostly implemented by equipment from Apple Computer, Inc.). The specification is recent, but nevertheless mature.
Applications will normally need to be modified to explicitly request port mappings from the operating system, which would then operate the NAT-PMP state machine and message handling. By design, the protocol allows applications to expose services to the outside, so hole-punching could conceivably be done automatically whenever an application listens to a local TCP port (although this would probably have unwelcome security implications).
To be completed [I‑D.wing‑behave‑nat‑control‑stun‑usage] (Wing, D., Rosenberg, J., and H. Tschofenig, “Discovering, Querying, and Controlling Firewalls and NATs,” October 2007.).
To be completed [RFC3103] (Borella, M., Grabelsky, D., Lo, J., and K. Taniguchi, “Realm Specific IP: Protocol Specification,” October 2001.).
Application Listener Discovery for IPv6 [I‑D.woodyatt‑ald] (Woodyatt, J., “Application Listener Discovery (ALD) for IPv6,” July 2008.) is a light-weight, binary protocol to explicitly punch holes through stateful IPv6 firewalls. It uses ICMPv6 for signaling and is auto-configured through an explicit ICMPv6 router advertisement option.
If the gateway supports ALD, a host can request the opening of holes for any incoming packet toward its own IPv6 address, based on one of multiple possible criteria:
Holes automatically expire if not refreshed before a negotiated timeout. The gateway can additionally notify hosts through unsolicited advertisements if it has rebooted or lost state.
ALD is aimed at unmanaged IPv6 networks, where it might not be acceptable to pass any unsolicited packets coming from the outside toward any hosts in the internal network. ALD needs support from all IPv6 routers within the network, because clients learn the ALD middlebox address through IPv6 Neighbor Discovery auto-configuration. It is expected that ALD will operate on the router itself in most cases. As with IPv6 Neighbor Discovery, there is no authentication.
The specification is currently a work-in-progress; there is no known deployment to date. Applications would supposedly need slight modifications, similar as with [UPNP] (UPnP Forum, “Internet Gateway Device (IGD) Standardized Device Control Protocol V 1.0,” November 2001.) or [I‑D.cheshire‑nat‑pmp] (Cheshire, S., “NAT Port Mapping Protocol (NAT-PMP),” April 2008.).
ALD can handle "pinholes" for any transport protocol, although it is limited to IPv6 networks, and is meant to restore the ability to operate general-purpose servers behind stateful firewalls. It currently does not explicitly support nesting, though ALD middleboxes could probably forward pinholes request in a hierarchical manner (from innermost to outermost device).
To be completed [I‑D.shore‑nls‑fw] (Shore, M., “The NLS Firewall Application,” February 2006.).
To be completed [I‑D.shore‑afwc] (Shore, M. and D. McGrew, “An Authorized IP Firewall Control Application,” September 2006.).
This document is a survey of existing protocols and does not raise any new security considerations. The security considerations of the surveyed protocols are discussed in their respective specifications, at least for protocols developed within the IETF.
This document raises no IANA considerations.
The authors would like to thank Pasi Eronen, Albrecht Schwarz and Dan Wing for their comments on this document.
Dave Thaler provided information on the "Works with Windows Vista" and "Certified for Windows Vista" logo program [VISTALOGO] (Microsoft Corporation, “Windows Logo Program Device Requirements for Windows Vista Client and Windows Server code named 'Longhorn' (Version 3.09),” December 2006.).
|[I-D.cheshire-nat-pmp]||Cheshire, S., “NAT Port Mapping Protocol (NAT-PMP),” draft-cheshire-nat-pmp-03 (work in progress), April 2008 (TXT).|
|[I-D.ietf-behave-multicast]||Wing, D. and T. Eckert, “IP Multicast Requirements for a Network Address (and port) Translator (NAT),” draft-ietf-behave-multicast-12 (work in progress), November 2007 (TXT).|
|[I-D.ietf-behave-nat-icmp]||Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, “NAT Behavioral Requirements for ICMP protocol,” draft-ietf-behave-nat-icmp-12 (work in progress), January 2009 (TXT).|
|[I-D.ietf-behave-tcp]||Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. Srisuresh, “NAT Behavioral Requirements for TCP,” draft-ietf-behave-tcp-08 (work in progress), September 2008 (TXT).|
|[I-D.ietf-nsis-nslp-natfw]||Stiemerling, M., Tschofenig, H., Aoun, C., and E. Davies, “NAT/Firewall NSIS Signaling Layer Protocol (NSLP),” draft-ietf-nsis-nslp-natfw-25 (work in progress), April 2010 (TXT).|
|[I-D.ietf-nsis-ntlp]||Schulzrinne, H. and M. Stiemerling, “GIST: General Internet Signalling Transport,” draft-ietf-nsis-ntlp-20 (work in progress), June 2009 (TXT).|
|[I-D.manner-nsis-nslp-auth]||Manner, J., Stiemerling, M., Tschofenig, H., and R. Bless, “Authorization for NSIS Signaling Layer Protocols,” draft-manner-nsis-nslp-auth-04 (work in progress), July 2008 (TXT).|
|[I-D.shore-afwc]||Shore, M. and D. McGrew, “An Authorized IP Firewall Control Application,” draft-shore-afwc-00 (work in progress), September 2006 (TXT).|
|[I-D.shore-nls-fw]||Shore, M., “The NLS Firewall Application,” draft-shore-nls-fw-00 (work in progress), February 2006 (TXT).|
|[I-D.wing-behave-nat-control-stun-usage]||Wing, D., Rosenberg, J., and H. Tschofenig, “Discovering, Querying, and Controlling Firewalls and NATs,” draft-wing-behave-nat-control-stun-usage-05 (work in progress), October 2007 (TXT).|
|[I-D.woodyatt-ald]||Woodyatt, J., “Application Listener Discovery (ALD) for IPv6,” draft-woodyatt-ald-03 (work in progress), July 2008 (TXT).|
|[RFC1928]||Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and L. Jones, “SOCKS Protocol Version 5,” RFC 1928, March 1996 (TXT).|
|[RFC3103]||Borella, M., Grabelsky, D., Lo, J., and K. Taniguchi, “Realm Specific IP: Protocol Specification,” RFC 3103, October 2001 (TXT).|
|[RFC3303]||Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and A. Rayhan, “Middlebox communication architecture and framework,” RFC 3303, August 2002 (TXT).|
|[RFC4540]||Stiemerling, M., Quittek, J., and C. Cadar, “NEC's Simple Middlebox Configuration (SIMCO) Protocol Version 3.0,” RFC 4540, May 2006 (TXT).|
|[RFC4787]||Audet, F. and C. Jennings, “Network Address Translation (NAT) Behavioral Requirements for Unicast UDP,” BCP 127, RFC 4787, January 2007 (TXT).|
|[UPNP]||UPnP Forum, “Internet Gateway Device (IGD) Standardized Device Control Protocol V 1.0,” November 2001.|
|[VISTALOGO]||Microsoft Corporation, “Windows Logo Program Device Requirements for Windows Vista Client and Windows Server code named 'Longhorn' (Version 3.09),” December 2006.|
|Nokia Research Center|
|P.O. Box 407|
|Nokia Group FIN-00045|
|Phone:||+358 50 4824461|
|Nokia Research Center|
|P.O. Box 407|
|Nokia Group FIN-00045|
|Phone:||+358 50 4876607|
|Nokia Technology Platforms|
|P.O. Box 407|
|Nokia Group FIN-00045|
|Phone:||+358 50 4876315|
|Nokia Technology Platforms|
|P.O. Box 407|
|Nokia Group FIN-00045|
|Phone:||+358 50 3860572|
|Nokia Siemens Networks|
|Munich, Bavaria 81739|
Copyright © The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an “AS IS” basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at firstname.lastname@example.org.