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Copyright (C) The Internet Society (2004). All Rights Reserved.
Most of the firewalls deployed today are Mobile IPv6 unaware. Widespread Mobile IPv6 deployment is not possible unless Mobile IPv6 messages are allowed to pass through these firewalls. A signaling protocol is needed which can communicate with these firewalls and instruct them to bypass these Mobile IPv6 messages. The goal of this document is to describe the interaction between NSIS and Mobile IPv6 for successful deployment of Mobile IPv6.
1.
Introduction
2.
Terminology
3.
Route Optimization
3.1
Correspondant Node (CN) behind a firewall
3.2
Mobile Node (MN) behind a firewall
3.3
Home Agent (HA) behind a firewall
4.
Other Routing Considerations
4.1
Triangular routing (CN behind Firewall)
4.2
Bi-directional routing (MN behind firewall)
5.
Security Considerations
6.
Acknowledgements
7.
Open Issues
§.
Normative References
§.
Informative References
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
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Route optimization, an integral part of Mobile IPv6 specification does not work with state of the art firewalls that employ stateful packet filtering. This problem is well described in [I-D.le-mip6-firewalls]Le, F., Mobile IPv6 and Firewalls, February 2004.. There is a need for identifying a signaling protocol that can install some firewall rules to allow these Mobile IPv6 messages to pass through. The NSIS NAT/FW NSLP described in [I-D.ietf-nsis-nslp-natfw]Stiemerling, M., Tschofenig, H. and M. Martin, A NAT/Firewall NSIS Signaling Layer Protocol (NSLP), February 2004., allows other protocols to establish/maintain/delete Middlebox state(NAT bindings and Firewall rules). We identify NSIS as possible solution to the aforementioned problem and describe the solution in detail.
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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]Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, March 1997..
Furthermore, we use the same terminology as in [RFC3775]Johnson, D., Perkins, C. and J. Arkko, Mobility Support in IPv6, June 2004., [I-D.ietf-nsis-nslp-natfw]Stiemerling, M., Tschofenig, H. and M. Martin, A NAT/Firewall NSIS Signaling Layer Protocol (NSLP), February 2004., and [I-D.ietf-nsis-requirements]Brunner, M., Requirements for Signaling Protocols, April 2004..
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In this section we will consider the application of NSIS signaling for some simple scenarios. It is to be noted that a real scenario could include a combination of these cases. In all the scenarios, we assume that the Correspondant Node(CN), Mobile Node(MN) and the Firewalls(FW) are NSIS aware. When we mention that a network is protected by a firewall, we assume that there is one central firewall for the whole network. This assumption will be relaxed in the later versions of this draft.
In Figure 1CN behind the firewall scenario, the correspondant node (CN) is protected by a firewall that employs stateful packet filtering (SPF). The external mobile node (MN) and its associated home agent (HA) are also shown in the figure. The MN is in its home network and is communicating with CN. Here it is assumed that CN has initiated the communication and hence it has no problems with the SPF.
The MN moves out of its home network and has to perform the return routability test (RRT) before sending the binding update to the CN. It sends a home test init (HoTI) message through the HA to the CN and expects a home test (HoT) message from the CN in the same path. It also sends a Careof test init (CoTI) message directly to the CN and expects Careof test (CoT) message in the same path from the CN. The SPF will only allow packets that belong to an existing session and hence will drop the COTI packet as this packet has a new source address.
+----------------+ +----+
| | | HA |
| | +----+
| | Home Agent
| +----+ +----+ of MN
| | CN | | FW |
| +----+ +----+
| | +----+
| | | MN |
| | +----+
+----------------+ External Mobile
Network protected Node
by a firewall
| CN behind the firewall scenario |
The MN initiates the NSIS session by sending a 'create-session' message to the CN. The FW may not necessarily know the MN and it may not be able to authenticate the MN. Hence it stores some relevant state regarding this 'firewall policy installation' request and waits for the CN's authentication result. Once the CN approves the request, the FW will install the relevant policy requested by the MN. When the MN receives both the messages CoT and HoT, it will construct the binding key and perform binding update to the CN. Note, the signaling that was aforementioned was only to allow the Mobile IPv6 messages. This will be referred to as Signaling-C from hereon. If the CN wants to continue sending data traffic to the new CoA, it can do so without any additional signaling. But if the MN wants to continue sending data traffic, it has to perform one more round of signaling to install filter rules for data traffic. This will be referred to as Signaling-D from hereon. The possibility of combined signaling is a topic for further discussion. The message flow for NSIS signaling is shown in Figure 2NSIS signaling for CN behind the firewall . Note, only the message flow between MN and CN is shown in the diagram.
+-----------------------+ +----+
| | | HA |
| | +----+
| | Home Agent
| | of MN
| |
| |
|+----+ +-----+
|| | | | CREATE-SESSION +----+
|| +--------<-----+ +---------<----------+ |
|| | PATH-SUCCEED | | | |
|| +-------->-----+ +--------->----------+ |
|| CN | | FW | CoTI | MN |
|| +--------<-----+ +---------<----------+ |
|| | CoT | | | |
|| +-------->-----+ +--------->----------+ |
|| | | | Binding update | |
|| +--------<-----+ +---------<----------+ |
|| | | | Binding ACK | |
|| +-------->-----+ +--------->----------+ |
|| | | | | |
|+----+ +-----+ +----+
| |
| | External Mobile
| | Node
+-----------------------+
Network protected
by a firewall
| NSIS signaling for CN behind the firewall |
In Figure 3MN behind the firewall scenario, the least problematic scenario is shown. This is because the MN is protected by the firewall and all the messages initiated by the MN will be bypassed. Immediatly after moving to a new network, the MN acquires a new CoA and it performs the binding update to the HA. The RRT procedure follows and then it performs the binding update to the CN. If the MN wants to continue sending data traffic, then no NSIS signaling is needed at all for this scenario. However, if the CN wants to send data traffic, CN has to initiate Signaling-D.
Home Network
+----------------+
| |
| +----+ |
| | HA | |
| +----+ |
| : |
+----------------+ | : |
| | | : |
| | +---------:------+
| +----+ | :
| | CN | | :
| +----+ | :
| | v
| | :
+----------------+ +---------:------+
CN's Network | : |
| : |
+----+ +----+ |
| FW | | MN | |
+----+ +----+ |
| |
| |
+----------------+
Visited Network
...... = Mobility direction
| MN behind the firewall scenario |
This is a special case which requires the HA also to be NSIS aware.
The first thing the MN has to do after entering a new network is to send a binding update to the HA. But as it is initiated by the MN, it first has to install some filter rules in the FW before sending the binding update. Hence, it initiates the NSIS Signaling-C to create rules that will allow the binding update messages.
Then it performs the binding update to the HA. The MN-HA binding update message is assumed to be IPsec protected. This might cause problems, as some firewalls do not allow IPsec traffic. Hence UDP encapsulation of IPsec traffic might be needed to alleviate this problem. The authors are awaiting feedback from the MIP6 WG which is currently discussing the possibility of using Authentication Data field to carry Binding Update/Acknowledgement. This might be a possible alternative for Binding update protection.
The firewall rules previously installed will also allow the HoTI message. The HA will then send the HoTI to CN and obviously this message is allowed as it is initiated by the HA. The HoT message from CN to HA is also allowed by the SPF as it belongs to the session previously initiated by the HA. The HoT message from HA to MN is also allowed as it is initiated by the HA. The RRT completes successfully.
Now the MN has to perform Signaling-D so that the tunneled packets will be allowed by the FW. Detailed message flow is shown in Figure 4NSIS signaling for HA behind the firewall. Note, only the interaction between HA and MN is shown in the figure.
+------------------------+ +----+
| | | CN |
| | +----+
| | Correspondant node
| |
| +----+ +-----+ +------------------+
| | | | | CREATE-SESSION | +----+ |
| | +--------<-----+ +---------<------|---<---+ | |
| | | PATH-SUCCEED | | | | | |
| | +-------->-----+ +--------->------|--->---+ | |
| | | | | Binding update | | | |
| | +--------<-----+ +---------<------|---<---+ | |
| | | | | Binding ACK | | | |
| | +-------->-----+ +--------->------|--->---+ | |
| | | | | HoTI | | | |
| | +--------<-----+ +---------<------|---<---+ | |
| | | | | HoT | | | |
| | +-------->-----+ +--------->------|--->---+ | |
| | HA | | FW | | | | |
| | | | | | | MN | |
| | | | | | | | |
| | | | | CREATE-SESSION | | | |
| | +--------<-----| +---------<------|---<---+ | |
| | | PATH-SUCCEED | | | | | |
| | +-------->-----+ +--------->------|--->---+ | |
| | | | | DATA | | | |
| | +========<=====+ +=========<======|===<===+ | |
| | | | | | | | |
| +----+ +-----+ | +----+ |
| | | |
| | | |
+------------------------+ +------------------+
HA protected by firewall Visited Network
(Home Network)
| NSIS signaling for HA behind the firewall |
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In this section we will consider the application of NSIS signaling for the other routing scenarios namely:
We will treat only some scenarios here. More scenarios will be treated in later versions of this draft.
In this routing mode, the CN sends the packets with MN's HoA as the destination address and CN's address as the source address. The HA intercepts it and encapsulates this packet as explained in [RFC2473]Conta, A. and S. Deering, Generic Packet Tunneling in IPv6 Specification, December 1998.. The HA then sends the encapsulated packet to the MN which has HA's address as the source address and MN's address as the destination address. The MN decapsulates the packet and gets to know the address of the CN. The MN now sends the packets directly to the CN.
Consider the scenario shown in Figure 5NSIS signaling for CN behind the firewall in triangular routing. The CN is protected by a FW that has SPF functionality. It will not allow the packets in the other direction as it does not belong to any connection that exists already.
Hence, the MN has to initiate Signaling-D by sending the 'create-session' message to the CN and the FW will install the policies when it receives the 'path-succeed' message. Now the MN is allowed to communicate in the reverse direction.
+-------------------------+ Home Agent
| | of MN
| +-----+ +-----+ +----+
| | | | | Tunneled packets | HA |
| | +******>*******+ +**********>*********+ |
| | | | | +-+--+
| | | | | *
| | | | | *
| | | | | v
| | CN | | FW | *
| | | | | CREATE-SESSION +-+--+
| | +--------<-----+ +---------<----------+ |
| | | PATH-SUCCEED | | | |
| | +-------->-----+ +--------->----------+ |
| | | | | | |
| | | | | Data traffic | MN |
| | +********<*****+ +*********<**********+ |
| | | | | | |
| +-----+ +-----+ +----+
| |
| | External Mobile
| | Node
+-------------------------+
Network protected
----- = signaling traffic
***** = Data traffic
| NSIS signaling for CN behind the
firewall in triangular routing |
If we consider the scenario of the CN being protected by a firewall, there is no need for any signaling. The CN initiates the data transfer and hence the SPF will store relevant connection information and allow the packets in the reverse direction. If we consider the scenario where the MN is protected by a SPF, then we would require an NSIS aware HA. Even though the MN had earlier initiated a connection for the purpose of binding update, new filter rules have to be installed to allow the tunneled data traffic. The message flow is shown in Figure 6NSIS signaling for CN behind the firewall in bi-directional tunneling.
Network protected
+-------------------------+ External Mobil
| | Node
| +-----+ +-----+ +----+
| | | | | | |
| | |Binding update| | | |
| | |-------->-----+ +--------->----------+ |
| | | | | Binding ACK | |
| | |--------<-----+ +---------<----------+ |
| | | | | | |
| | MN | | FW | CREATE-SESSION | MN |
| | +--------<-----+ +---------<----------+ |
| | | PATH-SUCCEED | | | |
| | +-------->-----+ +--------->----------+ |
| | | | | | |
| | | | | | |
| | | | | | |
| | | | | Data traffic | |
| | +**************+ +********************+ |
| | | | | | |
| +-----+ +-----+ +----+
| | *
| | *
| | *
+-------------------------+ *
*
+----+
| CN |
+----+
----- = signaling traffic Correspondant
***** = Data traffic (both direction) node
| NSIS signaling for CN behind the
firewall in bi-directional tunneling |
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TBD
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Many parts of this documents are the result of some discussions within the NAT/firewall-NSLP-team including: Marcus Brunner, Miquel Martin, Martin Stiemerling, and Cedric Aoun.
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| [RFC3775] | Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. |
| [I-D.le-mip6-firewalls] | Le, F., "Mobile IPv6 and Firewalls", draft-le-mip6-firewalls-00 (work in progress), February 2004 (TXT). |
| [I-D.ietf-nsis-nslp-natfw] | Stiemerling, M., Tschofenig, H. and M. Martin, "A NAT/Firewall NSIS Signaling Layer Protocol (NSLP)", draft-ietf-nsis-nslp-natfw-01 (work in progress), February 2004 (TXT). |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. |
| [RFC2473] | Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998 (TXT, HTML, XML). |
| [I-D.ietf-nsis-requirements] | Brunner, M., "Requirements for Signaling Protocols", draft-ietf-nsis-requirements (work in progress), April 2004 (TXT). |
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| [I-D.aoun-nsis-nslp-natfw-migration] | Aoun, C., Brunner, M., Stiemerling, M., Martin, M. and H. Tschofenig, "NAT/Firewall NSLP Migration Considerations", draft-aoun-nsis-nslp-natfw-migration-01 (work in progress), February 2004 (TXT). |
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| Srinath Thiruvengadam | |
| Siemens | |
| Otto-Hahn-Ring 6 | |
| Munich, Bayern 81739 | |
| Germany | |
| EMail: | srinath@mytum.de |
| Hannes Tschofenig | |
| Siemens | |
| Otto-Hahn-Ring 6 | |
| Munich, Bayern 81739 | |
| Germany | |
| EMail: | Hannes.Tschofenig@siemens.com |
| Franck Le | |
| Nokia Research Center | |
| 6000 Connection Drive, Irving | |
| Dallas, Texas 75063 | |
| USA | |
| EMail: | franck.le@nokia.com |
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