Network Working Group M. Blanchet
Internet-Draft F. Parent
Expires: November 13, 2005 Hexago
May 12, 2005
IPv6 Tunnel Broker with the Tunnel Setup Protocol (TSP)
draft-blanchet-v6ops-tunnelbroker-tsp-02
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
A tunnel broker with the Tunnel Setup Protocol (TSP) enables the
establishment of tunnels of various inner protocols, such as IPv6 or
IPv4, inside various outer protocols packets, such as IPv4, IPv6 or
UDP over IPv4 for IPv4 NAT traversal. The control protocol (TSP) is
used by the tunnel client to negotiate the tunnel with the broker. A
mobile node implementing TSP can be connected to both IPv4 and IPv6
networks whether it is on IPv4 only, IPv4 behind a NAT or on IPv6
only. A tunnel broker may terminate the tunnels on remote tunnel
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servers or on itself. This document describes the TSP protocol
within the model of the tunnel broker model.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Description of the TSP framework . . . . . . . . . . . . . . . 4
2.1 NAT Discovery . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Any encapsulation . . . . . . . . . . . . . . . . . . . . 6
2.3 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Advantages of TSP . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 7
4.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
4.2 Topology . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4 TSP signaling . . . . . . . . . . . . . . . . . . . . . . 9
4.4.1 Signaling transport . . . . . . . . . . . . . . . . . 9
4.4.2 Authentication phase . . . . . . . . . . . . . . . . . 11
4.4.3 Command and response phase . . . . . . . . . . . . . . 14
4.5 Tunnel establishment . . . . . . . . . . . . . . . . . . . 16
4.5.1 IPv6-over-IPv4 tunnels . . . . . . . . . . . . . . . . 16
4.5.2 IPv6-over-UDP tunnels . . . . . . . . . . . . . . . . 16
4.6 Tunnel Keep-alive . . . . . . . . . . . . . . . . . . . . 16
4.7 XML Messaging . . . . . . . . . . . . . . . . . . . . . . 17
4.7.1 Tunnel . . . . . . . . . . . . . . . . . . . . . . . . 17
4.7.2 Client Element . . . . . . . . . . . . . . . . . . . . 18
4.7.3 Server Element . . . . . . . . . . . . . . . . . . . . 18
4.7.4 Broker Element . . . . . . . . . . . . . . . . . . . . 18
5. Tunnel request examples . . . . . . . . . . . . . . . . . . . 19
5.1 Host tunnel request and reply . . . . . . . . . . . . . . 19
5.2 Router Tunnel request with a /48 prefix delegation,
and reply . . . . . . . . . . . . . . . . . . . . . . . . 19
5.3 IPv4 over IPv6 tunnel request . . . . . . . . . . . . . . 21
5.4 NAT Traversal tunnel request . . . . . . . . . . . . . . . 21
6. Applicability of TSP in Different Environments . . . . . . . . 22
6.1 Applicability of TSP in Provider Networks with
Enterprise Customers . . . . . . . . . . . . . . . . . . . 22
6.2 Applicability of TSP in Provider Networks with
Home/Small Office Customers . . . . . . . . . . . . . . . 23
6.3 Applicability of TSP in Enterprise Networks . . . . . . . 23
6.4 Applicability of TSP in Wireless Networks . . . . . . . . 23
6.5 Applicability of TSP in Unmanaged networks . . . . . . . . 24
6.6 Applicability of TSP for Mobile Hosts and Mobile
Networks . . . . . . . . . . . . . . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 25
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
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11. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.1 Normative References . . . . . . . . . . . . . . . . . . . 25
11.2 Informative References . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 26
A. The TSP DTD . . . . . . . . . . . . . . . . . . . . . . . . . 27
B. Error codes . . . . . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . . . 29
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1. Introduction
This document first describes the TSP framework, the protocol
details, and the different profiles used. It then describes the
applicability of TSP in different environments, some of which were
described in the v6ops scenario documents.
2. Description of the TSP framework
Tunnel Setup Protocol (TSP) is a signaling protocol to setup tunnel
parameters between two tunnel end-points. TSP is implemented as a
tiny client code in the requesting tunnel end-point. The other end-
point is the server that will setup the tunnel service. TSP uses XML
basic messaging over TCP or UDP. The use of XML gives extensibility
and easy option processing.
TSP negotiates tunnel parameters between the two tunnel end-points.
Parameters that are always negociated are:
o authentication of the users, using any kind of authentication
mechanism (through SASL [RFC2222]) including anonymous
o Tunnel encapsulation
* IPv6 over IPv4 tunnels [RFC2893]
* IPv4 over IPv6 tunnels
* IPv6 over UDP-IPv4 tunnels
o IP address assignment for the tunnel endpoints
Other tunnel parameters that may be negotiated are:
o Tunnel keep-alive
o IPv6 prefix assignment when the client is a router
o DNS delegation of the inverse tree, based on the IPv6 prefix
assigned
o Routing protocols
The tunnel encapsulation can be explicitly specified by the client,
or can be determined during the TSP exchange. The latter is used to
detect the presence of NAT in the path and select IPv6 over UDP
encapsulation.
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The TSP connection can be established between two nodes, where each
node can control a tunnel end-point.
The nodes involved in the framework are:
1. the TSP client
2. client tunnel end-point
3. the TSP server
4. server tunnel end-point
1,3 and 4 form the tunnel broker model [RFC3053], where 3 is the
tunnel broker and 4 is the tunnel server (Figure 1). The tunnel
broker may control one or many tunnel servers.
In its simplest model, one node is the client configured as a tunnel
end-point (1 and 2 on same node), and the second node is the server
configured as the other tunnel end-point (3 and 4 on same node).
This model is shown in Figure 2
_______________
| TUNNEL BROKER |--> Databases (DNS)
| |
| TSP |
| SERVER |
|_______________|
| |
__________ | | ________
| | | | | |
| TSP |--[TSP]-- +---------| |
| CLIENT | | TUNNEL |--[NETWORK]--
[HOST]--| |<==[CONFIGURED TUNNEL]==>| SERVER |
|___________| | |
|________|
Figure 1: Tunnel Setup Protocol used on Tunnel Broker model
___________ ________
| | | TSP |
| TSP |-----------[TSP]---------| SERVER |
| CLIENT | | |--[NETWORK]--
[HOST]--| |<==[CONFIGURED TUNNEL]==>| TUNNEL |
|___________| | SERVER |
|________|
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Figure 2: Tunnel Setup Protocol used on Tunnel Server model
From the point of view of an operating system, TSP is implemented as
a client application which is able to configure network parameters of
the operating system.
2.1 NAT Discovery
TSP is also used to discover if a NAT is in the path. In this
discovery mode, the client sends a TSP message over UDP, containing
its tunnel request information (such as its source IPv4 address) to
the TSP server. The TSP server compares the IPv4 source address of
the packet with the address in the TSP message. If they differ, an
IPv4 NAT is in the path.
If an IPv4 NAT is discovered, then IPv6 over UDP-IPv4 tunnel
encapsulation is selected. Once the TSP signaling is done, the
tunnel is established over the same UDP channel used for TSP, so the
same NAT address-port mapping is used for both the TSP session and
the IPv6 traffic. If no IPv4 NAT is detected in the path by the TSP
server, then IPv6 over IPv4 encapsulation is used.
A keep-alive mechanism is also included to keep the NAT mapping
active.
The IPv4 NAT discovery builds the most effective tunnel for all
cases, including in a dynamic situation where the client moves. On
the IPv6 layer, if the client uses user authentication, the same IPv6
address and prefix are kept and re-established.
2.2 Any encapsulation
TSP is used to negotiate IPv6 over IPv4 tunnels, IPv6 over UDP-IPv4
tunnels and IPv4 over IPv6 tunnels. IPv4 over IPv6 tunnels are used
in the Dual Stack Transition Mechanism (DSTM) together with TSP
[I-D.ietf-ngtrans-dstm].
2.3 Mobility
When a node moves to a different IP network (i.e. change of its IPv4
address when doing IPv6 over IPv4 encapsulation), the TSP client
reconnects automatically to the broker to re-establish the tunnel
(keep-alive mechanism). The IPv6 address does not change.
3. Advantages of TSP
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o Tunnels established by TSP are static tunnels, which are more
secure than automated tunnels. No 3rd party relay required.
o Stability of the IP address and prefix, enabling applications
needing stable address to be deployed and used. For example, when
tunneling IPv6, there is no dependency on the underlying IPv4
address.
o Prefix assignment supported. Can use provider address space.
o Signaling protocol flexible and extensible (XML, SASL)
o One solution to many encapsulation techniques: v6 in v4, v4 in v6,
v6 over UDP over v4, ...
o Discovery of IPv4 NAT in the path, establishing the most optimized
tunnelling technique depending on the discovery.
4. Protocol Description
4.1 Terminology
Tunnel Broker (TB): In a tunnel broker model, the broker is taking
charge of all communication between tunnel servers (TS) and tunnel
clients (TC). Tunnel clients query brokers for a tunnel and the
broker finds a suitable tunnel server, asks the Tunnel server to
setup the tunnel and sends the tunnel information to the Tunnel
Client.
Tunnel Server (TS): Tunnel Servers are providing the specific tunnel
service to a Tunnel Client. It can receive the tunnel request
from a Tunnel Broker (as in the Tunnel Broker model) or directly
from the Tunnel Client. The Tunnel Server is the tunnel end-
point.
Tunnel Client (TC): The tunnel client is the entity that needs a
tunnel for a particular service or connectivity. A tunnel client
can be either a host or a router. The tunnel client is the other
tunnel end-point.
v6v4: IPv6-over-IPv4 tunnel encapsulation
v6udpv4: IPv6-over-UDP-over-IPv4 tunnel encapsulation
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v4v6: IPv4-over-IPv6 tunnel encapsulation
4.2 Topology
The following diagrams describe typical TSP scenarios. The goal is
to establish a tunnel between Tunnel client and Tunnel server.
4.3 Overview
The Tunnel Setup Protocol is initiated from a client node to a tunnel
broker. The Tunnel Setup Protocol has three phases:
Authentication phase: The Authentication phase is when the tunnel
broker/server advertises its capability to a tunnel client and
when a tunnel client authenticate to the broker/server.
Command phase: The command phase is where the client requests or
updates a tunnel.
Response phase: The response phase is where the tunnel client
receives the request response from the tunnel broker/server, and
the client accepts or rejects the tunnel offered.
For each command sent by a Tunnel Client there is an expected
response by the server.
After the response phase is completed, a tunnel is established as
requested by the client. If requested, periodic keep-alive packets
can be sent from the client to the server.
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tunnel tunnel
client broker
+| Send version +
||---------------------------------> ||
|| Send capabilities ||
||<--------------------------------- +| Authentication
|| SASL authentication || phase
||<--------------------------------> ||
TSP || Authentication OK ||
signaling||<--------------------------------- +
|| Tunnel request || Command
||---------------------------------> || phase
|| Tunnel response +
||<--------------------------------- || Response
|| Tunnel acknowledge || phase
||---------------------------------> +
+| |
|| Tunnel established |
Data ||===================================|
phase || |
+| (keep-alive) |
Figure 3: Tunnel Setup Protocol exchange
4.4 TSP signaling
The following sections describes in detail the TSP protocol and the
different phases in the TSP signaling.
4.4.1 Signaling transport
TSP signaling can be transported over TCP or UDP, and over IPv4 or
IPv6. The tunnel client selects the transport according to the
tunnel encapsulation to be requested. Figure 4 shows the transport
used for TSP signaling with possible tunnel encapsulation requested.
TSP signaling over UDP/v4 MUST be used if a v6 over UDP over IPv4
(v6udpv4) tunnel is to be requested (e.g., for NAT traversal).
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Tunnel
Encapsulation Valid Valid
Requested Transport Address family
------------------------------------------
v6v4 TCP UDP IPv4
v6udpv4 UDP IPv4
v4v6 TCP UDP IPv6
Figure 4: TSP signaling transport
Note that the TSP framework allows for other type of encapsulation to
be defined, such as IPv6 over GRE.
4.4.1.1 TSP signaling over TCP
TSP over TCP is sent over port number 3653 (IANA assigned). TSP data
used during signaling is detailed in the next sections.
+------+-----------+----------+
| IP | TCP | TSP data |
| | port 3653 | |
+------+-----------+----------+
where IP is IPv4 or IPv6
Figure 5: Tunnel Setup Protocol packet format (TCP)
4.4.1.2 TSP signaling over UDP/v4
While TCP provides the connection-oriented and reliable data delivery
features required during the TSP signaling session, UDP does not
offer any reliability. This reliability is added inside the TSP
session as an extra header at the beginning of the UDP payload.
+------+-----------+------------+----------+
| IPv4 | UDP | TSP header | TSP data |
| | port 3653 | | |
+------+-----------+------------+----------+
Figure 6: Tunnel Setup Protocol packet format (UDP)
The algorithm used to add reliability to TSP packets sent over UDP is
described in section 22.5 in [UNP].
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xF | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TSP data |
...
Figure 7: TSP header for reliable UDP
The four bit field (0-3) is set to 0xF. This marker is used by
the tunnel broker to identify a TSP signaling packets that is sent
after an IPv6 over UDP is established. This is explained in
section Section 4.5.2
Sequence Number: 28 bit field. Set by the tunnel client. Value is
increased by one for every new packet sent to the tunnel broker.
The return packet from the broker contains the unaltered sequence
number.
Timestamp: 32 bit field. Set by the tunnel client. Generated from
the client local time value. The return packet from the broker
contains the unaltered timestamp.
TSP data: Same as in the TCP/v4 case. Content described in latter
sections.
The TSP client builds its UDP packet as described above and sends it
to the tunnel broker. When the tunnel broker responds, the same
values for the sequence number and timestamp MUST be sent back to the
client. The TSP client can use the timestamp to determine the
retransmission timeout (current time minus the packet timestamp).
The client SHOULD retransmit the packet when the retransmission
timeout is reached. The retransmitted packet MUST use the same
sequence number as the original packet so that the server can detect
duplicate packets. The client SHOULD use exponential backoff when
retranmitting packets to avoid network congestion.
4.4.2 Authentication phase
The authentication phase has 3 steps :
o Client's protocol version identification
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o Server's capability advertisement
o Client authentication
When a TCP or UDP session is established to a tunnel broker, the
tunnel client sends the current protocol version it is supporting.
The version number syntax is:
VERSION=2.0.0 CR LF
Version 2.0.0 is the version number of this specification. Version
1.0.0 was defined in earlier drafts.
If the server doesn't support the protocol version it sends an error
message and closes the session. The server can optionally send a
server list that may support the protocol version of the client.
Example of a Version not supported (without a server list)
-- Successful TCP Connection --
C:VERSION=0.1 CR LF
S:302 Unsupported client version CR LF
-- Connection closed --
Figure 8
Example of a version not supported (with a server list)
-- Successful TCP Connection --
C:VERSION=1.1 CR LF
S:1302 Unsupported client version CR LF
1.2.3.4
ts1.isp1.com
-- Connection closed --
Figure 9
If the server supports the version sent by the client, then the
server sends a list of the capabilities supported for authentication
and tunnels.
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CAPABILITY TUNNEL=V6V4 TUNNEL=V6UDPV4 AUTH=ANONYMOUS AUTH=PLAIN
AUTH=DIGEST-MD5 CR LF
Tunnel types must be registered with IANA and their profiles are
defined in Section 7. Authentication is done using SASL [RFC2222].
Each authentication mechanism must be a registered SASL mechanism.
Description of such mechanism is not in the scope of this document.
The tunnel client can then choose to close the session if none of the
capabilities fits its needs. If the tunnel client chooses to
continue, it authenticates to the server using one of the advertised
mechanism. If the authentication fails the server sends an error
message and closes the session.
The example in Figure 10 shows a failed authentication where the
tunnel client requests an anonymous authentication which is not
supported by the server. The following example in Figure 11 shows a
successful anonymous authentication.
-- Successful TCP Connection --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 AUTH=DIGEST-MD5 CR LF
C:AUTHENTICATE ANONYMOUS CR LF
S:300 Authentication failed CR LF
Figure 10: Example of failed authentication
-- Successful TCP Connection --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 TUNNEL=V6UDPV4 AUTH=ANONYMOUS AUTH=PLAIN AUTH=DIGEST-MD5 CR LF
C:AUTHENTICATE ANONYMOUS CR LF
S:200 Success CR LF
Figure 11: Successful anonymous authentication
Digest-MD5 authentication follows [RFC2831].
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-- Successful TCP Connection --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 TUNNEL=V6UDPV4 AUTH=ANONYMOUS AUTH=PLAIN
AUTH=DIGEST-MD5 CR LF
C:AUTHENTICATE DIGEST-MD5 CR LF
S:cmVhbG09aGV4b3Msbm9uY2U9MTExMzkwODk2OCxxb3A9YXV0aCxhbGdvcml0aG09bWQ1LXNlc3Ms
Y2hhcnNldD11dGY4
C:Y2hhcnNldD11dGY4LHVzZXJuYW1lPSJ1c2VybmFtZTEiLHJlYWxtPSJoZXhvcyIsbm9uY2U9IjEx
MTM5MDg5NjgiLG5jPTAwMDAwMDAxLGNub25jZT0iMTExMzkyMzMxMSIsZGlnZXN0LXVyaT0idHNw
L2hleG9zIixyZXNwb25zZT1mOGU0MmIzYzUwYzU5NzcxODUzZjYyNzRmY2ZmZDFjYSxxb3A9YXV0
aA= S:cnNwYXV0aD03MGQ1Y2FiYzkyMzU1NjhiZTM4MGJhMmM5MDczODFmZQ= S:200 Success CR LF
The base64-decoded version of the SASL exchange is:
S:realm="hexos",nonce="1113908968",qop="auth",algorithm=md5-sess,charset=utf8
C:charset=utf8,username="username1",realm="hexos",nonce="1113908968",nc=00000001,
cnonce="1113923311",digest-uri="tsp/hexos",
response=f8e42b3c50c59771853f6274fcffd1ca,qop=auth
S:rspauth=70d5cabc9235568be380ba2c907381fe
Once the authentication succeeds, the server sends a success return
code and the protocol enters the Command phase.
4.4.3 Command and response phase
The Command phase is where the tunnel client send a tunnel request or
a tunnel update to the server. In this phase, commands are sent as
XML messages. The first line is a "Content-length" directive that
indicates the size of the following XML message. When the server
sends a response, the first line is the "Content-length" directive,
the second is the return code and third one is the XML message if
any. The "Content-length" is calculated from the first character of
the return code line to the last character of the XML message,
inclusively.
Spaces can be inserted freely.
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-- UDP session established --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 TUNNEL=V6UDPV4 AUTH=ANONYMOUS AUTH=PLAIN AUTH=DIGEST-MD5 CR LF
C:AUTHENTICATE ANONYMOUS CR LF
S:200 Success CR LF
C:Content-length: 205 CR LF
206.123.31.135
CR LF
S:Content-length: 501 CR LF
200 Success CR LF
206.123.31.115
3ffe:0bc0:8000:0000:0000:0000:0000:38b2
206.123.31.135
3ffe:0bc0:8000:0000:0000:0000:0000:38b3
3ffe:0bc0:8000:0000:0000:0000:0000:38b2
CR LF
C:Content-length: 35 CR LF
CR LF
Figure 14: Example of a command/response sequence
The example in Figure 14 shows a client requesting an anonymous
v6udpv4 tunnel, indicating that a keep-alive packet will be sent
every 30 seconds. The tunnel broker responds with the tunnel
parameters and indicates its acceptance of the keepalive period
(Section 4.6). Finally, the client sends an accept message to the
server.
Once the accept message has been sent, the server and client
configure their tunnel endpoint based on the negotiated tunnel
parameters.
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4.5 Tunnel establishment
4.5.1 IPv6-over-IPv4 tunnels
Once the TSP signaling is completed, a tunnel can be established on
the tunnel server and client node. If a v6v4 tunnel has been
negotiated, then an IPv6-over-IPv4 tunnel [RFC2893] is established
using the operating system tunneling interface. On the client node,
this is accomplished by the TSP client calling the appropriate OS
commands or system calls.
4.5.2 IPv6-over-UDP tunnels
If a v6udpv4 tunnel is configured, the same source/destination
address and port used during the TSP signaling are used to configure
the v6udpv4 tunnel. If a NAT is in the path between the TSP client
and tunnel broker, the TSP signaling session will have created a UDP
state in the NAT. By reusing the same UDP socket parameters to
transport IPv6, the traffic will flow across the NAT using the same
state.
+------+-----------+--------+
| IPv4 | UDP | IPv6 |
| | port 3653 | |
+------+-----------+--------+
Figure 15: IPv6 transport over UDP
At any time, a client may re-establish a TSP signaling session. The
client disconnects the current tunnel and starts a new TSP signaling
session as described in Section 4.4.1.2. If a NAT is present and the
new TSP session uses the same UDP mapping in the NAT as for the
tunnel, the tunnel broker will need to disconnect the client tunnel
before the client can establish a new TSP session.
4.6 Tunnel Keep-alive
A TSP client may select to send periodic keep-alive messages to the
server in order to maintain its tunnel connectivity. This allows the
client to detect network changes and enable automatic tunnel re-
establishment. In the case of IPv6-over-UDP tunnels, periodic keep-
alive can help refresh the connection state in a NAT if such device
is in the tunnel path.
For IPv6-over-IPv4 and IPv6-over-UDP tunnels, the keep-alive message
is an ICMPv6 echo request [RFC2463] sent from the client to the
tunnel server. The IPv6 destination address of the echo message MUST
be the address from the 'keepalive' element sent in the tunnel
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response during the TSP signaling (Section 4.4.3). The echo message
is sent over the configured tunnel.
The tunnel server responds to the ICMPv6 echo requests and can keep
track of which tunnel is active. Any client traffic can also be used
to verify if the tunnel is active. This can be used to disconnect
tunnels that are no longer in use.
The server can send a different keep-alive interval from the value
specified in the client request. The client MUST conform to the
server specified keep-alive interval. The client SHOULD apply a
random "jitter" value to avoid synchronization of keep-alive messages
from many clients to the server [FJ93]. This can be achieved by
using an interval value in the range of [0.75T - T], where T is the
keep-alive interval specified by the server.
4.7 XML Messaging
This section describes the XML messaging used in the TSP signaling
during the command and response phase. The XML elements and
attributes are listed in the DTD (Appendix A
4.7.1 Tunnel
The client and server use the tunnel token with an action attribute.
Valid actions for this profile are : 'create', 'delete', 'info',
'accept' and 'reject'.
create: action used to request a new tunnel or update an existing
tunnel. Sent from the tunnel client.
delete: action used to remove an existing tunnel from the server.
Sent from the tunnel client.
info: action used to request current properties of an existing
tunnel. This action is also used by the tunnel broker to send
tunnel parameters following a client 'create' action.
accept: action used by the client to acknowledge the server that the
tunnel parameters are accepted. The client will establish a
tunnel.
reject: action used by the client to signal the server that the
tunnel parameters offered are rejected and no tunnel will be
established.
The tunnel 'lifetime' attribute is set by the tunnel broker and
specifies the lifetime of the tunnel in minutes.The lifetime is an
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administratively set value. When a tunnel lifetime is expired, it is
disconnected on the tunnel server.
The 'tunnel' message contains three elements:
client Client's information
server Server's information
broker List of other server's
4.7.2 Client Element
The client element contains 2 elements: 'address' and 'router'.
These elements are used to describe the client request and will be
used by the server to create the appropriate tunnel. This is the
only element sent by a client.
The 'address' element is used to identify the client IP endpoint of
the tunnel. When tunneling over IPv4, the client MUST send only an
IPv4 address to the server. When tunneling over IPv6, the client
MUST only send an IPv6 address to the server.
The server then returns the assigned IPv6 or IPv4 address endpoint
and domain name inside the 'client' element when the tunnel is
created or updated. If supported by the server, the 'client' element
may contain the registered DNS name for the address endpoint assigned
to the client.
Optionally a client can send a 'router' element to ask for a prefix
delegation.
4.7.3 Server Element
The 'server' element contains 2 elements: 'address' and 'router'.
These elements are used to describe the server's tunnel endpoint.
The 'address' element is used to provide both IPv4 and IPv6 addresses
of the server's tunnel endpoint, while the 'router' element provides
information for the routing method chosen by the client.
4.7.4 Broker Element
The 'broker' element is used by a tunnel broker to provide a
alternate list of brokers to a client in the case where the server is
not able to provide the requested tunnel.
The 'broker' element contains a series of 'address' element(s).
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5. Tunnel request examples
This section presents multiple examples of requests.
5.1 Host tunnel request and reply
A simple tunnel request consist of a 'tunnel' element which contains
only an 'address' element. The tunnel action is 'create', specifying
a 'v6v4' tunnel encapsulation type. The response sent by the tunnel
broker is an 'info' action. Note that the registered FQDN of the
assigned client IPv6 address is also returned to the tunnel client.
-- Successful TCP Connection --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 AUTH=ANONYMOUS CR LF
C:AUTHENTICATE ANONYMOUS CR LF
S:200 Authentication successful CR LF
C:Content-length: 123 CR LF
1.1.1.1
CR LF
S: Content-length: 234 CR LF
200 OK CR LF
206.123.31.114
3ffe:b00:c18:ffff:0000:0000:0000:0000
1.1.1.1
3ffe:b00:c18:ffff::0000:0000:0000:0001
userid.domain
CR LF
C: Content-length: 35 CR LF
CR LF
Figure 16: Simple tunnel request made by a client
5.2 Router Tunnel request with a /48 prefix delegation, and reply
A tunnel request with prefix consist of a 'tunnel' element which
contains 'address' element and a 'router' element. The 'router'
element also contains the 'dns_server' element which is used to
request DNS delegation of the assigned IPv6 prefix. The 'dns_server'
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element lists the IP address of the DNS servers to be registered for
the reverse-mapping zone.
Tunnel request with prefix and static routes.
C: Content-length: 234 CR LF
1.1.1.1
2.3.4.5
2.3.4.6
3ffe:0c00::1
CR LF
S: Content-length: 234 CR LF
200 OK CR LF
206.123.31.114
3ffe:b00:c18:ffff:0000:0000:0000:0000
1.1.1.1
3ffe:b00:c18:ffff::0000:0000:0000:0001
userid.domain
3ffe:0b00:c18:1234::
2.3.4.5
2.3.4.6
3ffe:0c00::1
CR LF
C: Content-length: 35 CR LF
CR LF
Figure 17
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5.3 IPv4 over IPv6 tunnel request
This is similar to the previous 'create' action, but with the tunnel
type is set to 'v4v6'.
-- Successful TCP Connection --
C:VERSION=1.0 CR LF
S:CAPABILITY TUNNEL=V4V6 AUTH=DIGEST-MD5 AUTH=ANONYMOUS CR LF
C:AUTHENTICATE ANONYMOUS CR LF
S:OK Authentication successful CR LF
C:Content-length: 228 CR LF
3ffe:0b00:0c18:ffff:0000:0000:0000:0001
CR LF
If the allocation request is accepted, the broker will acknowledge
the allocation to the client by sending a 'tunnel' element with the
attribute 'action' set to 'info', 'type' set to 'v4v6' and the
'lifetime' attribute set to the period of validity or lease time of
the allocation. The 'tunnel' element contains 'server' and 'client'
elements.
S: Content-length: 370 CR LF
200 OK CR LF
206.123.31.2
3ffe:b00:c18:ffff:0000:0000:0000:0002
206.123.31.1
3ffe:b00:c18:ffff::0000:0000:0000:0001
CR LF
In DSTM [I-D.ietf-ngtrans-dstm] terminology, the DSTM server is the
TSP broker and the TEP is the tunnel server.
5.4 NAT Traversal tunnel request
When a client is capable of both IPv6 over IPv4 and IPv6 over UDP
over IPv4 encapsulation, it can request the broker, by using the
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"v6anyv4" tunnel mode, to determine if it is behind a NAT and to send
the appropriate tunnel encapsulation mode as part of the response.
The client can also explicitly request an IPv6 over UDP over IPv4
tunnel by specifying "v6udpv4" in its request.
In the following example, the client informs the server that it
requests to send keep-alives every 30 seconds. Its its response, the
server accepted the client suggested keep-alive interval, and the
IPv6 destination address for the keep-alive packets is specified.
-- Successful TCP Connection --
C:VERSION=2.0.0 CR LF
S:CAPABILITY TUNNEL=V6V4 TUNNEL=V6UDPV4 AUTH=DIGEST-MD5 CR LF
C:AUTHENTICATE ... CR LF
S:200 Authentication successful CR LF
C:Content-length: ... CR LF
10.1.1.1
CR LF
S: Content-length: ... CR LF
200 OK CR LF
206.123.31.114
3ffe:b00:c18:ffff:0000:0000:0000:0002
10.1.1.1
3ffe:b00:c18:ffff::0000:0000:0000:0003
3ffe:b00:c18:ffff:0000:0000:0000:0002
CR LF
6. Applicability of TSP in Different Environments
This section describes the applicability of TSP in different
environments.
6.1 Applicability of TSP in Provider Networks with Enterprise Customers
In a provider network where IPv4 is dominant, a tunnelled
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infrastructure can be used to provide IPv6 services to the enterprise
customers, before a full IPv6 native infrastructure is built. In
order to start deploying in a controlled manner and to give
enterprise customers a prefix, the TSP framework is used. The TSP
server can be in the core, in the aggregation points or in the PoPs
to offer the service to the customers. IPv6 over IPv4 encapsulation
can be used. If the customers are behind an IPv4 NAT, then IPv6 over
UDP-IPv4 encapsulation can be used. TSP can be used in combination
of other techniques.
6.2 Applicability of TSP in Provider Networks with Home/Small Office
Customers
In a provider network where IPv4 is dominant, a tunnelled
infrastructure can be used to provider IPv6 services to the home/
small office customers, before a full IPv6 native infrastructure is
built. The small networks such as Home/Small offices have a non-
upgradable gateway with NAT. TSP with NAT traversal is used to offer
IPv6 connectivity and a prefix to the internal network.
Automation of the prefix assignment and DNS delegation, done by TSP,
is a very important feature for a provider in order to substantially
decrease support costs. The provider can use the same AAA database
that is used to authenticate the dial in or IPv4 users. Customers
can deploy home IPv6 networks without any intervention of the
provider support people.
With the NAT discovery function of TSP, providers can use the same
TSP infrastructure for both NAT and non-NAT parts of the network.
6.3 Applicability of TSP in Enterprise Networks
In an enterprise network where IPv4 is dominant, a tunnelled
infrastructure can be used to provider IPv6 services to the IPv6
islands (hosts or networks) inside the enterprise, before a full IPv6
native infrastructure is built. TSP can be used to give IPv6
connectivity, prefix and routing for the islands. This gives to the
enterprise a full control deployment of IPv6 while maintaining
automation and permanence of the IPv6 assignments to the islands.
6.4 Applicability of TSP in Wireless Networks
In a wireless network where IPv4 is dominant, hosts and networks move
and change IPv4 address. TSP enables the automatic re-establishment
of the tunnel when the IPv4 address change.
In a wireless network where IPv6 is dominant, hosts and networks
move. TSP enables the automatic re-establishment of the tunnel
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together with the DSTM mechanism.
6.5 Applicability of TSP in Unmanaged networks
An unmanaged network is where no network manager or staff is
available to configure network devices. TSP is particularly powerful
in this context where automation of all necessary information for the
IPv6 connectivity is handled by TSP: tunnel end-points parameters,
prefix assignment, dns delegation, routing.
An unmanaged network may be behind a NAT, maybe not. With the NAT
discovery function, TSP works automatically in both cases.
6.6 Applicability of TSP for Mobile Hosts and Mobile Networks
Mobile hosts are common and used. Laptops moving from wireless,
wired in office, home, ... are examples. They often have IPv4
connectivity, but not necessarily IPv6. TSP framework enables the
mobile hosts to have IPv6 connectivity wherever they are, by having
the TSP client send updated information of the new environment to the
TSP server, when a change occurs. Together with NAT discovery and
traversal, the mobile host can be always IPv6 connected wherever it
is.
Mobile here means only the change of IPv4 address. Mobile-IP
mechanisms and fast hand-off take care of additional constraints in
mobile environments.
Mobile networks share the applicability of the mobile hosts.
Moreover, in the TSP framework, they also keep their prefix
assignment and can control the routing. NAT discovery can also be
used.
7. IANA Considerations
A tunnel type registry should be setup by IANA. The following
strings are defined in this document: "v6v4" for IPv6 in IPv4
encapsulation (using IPv4 protocol 41) "v6udpv4" for IPv6 in UDP in
IPv4 encapsulation "v6anyv4" for IPv6 in IPv4 or IPv6 in UDP in IPv4
encapsulation "v4v6" for IPv4 in IPv6 encapsulation.
Details on the registration procedure for new tokens TBD.
IANA assigned 3653 as the TSP port number.
8. Security Considerations
Authentication of the TSP session uses the SASL[RFC2222] framework,
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where the authentication mechanism is negotiated between the client
and the server. The framework enables to use the level of
authentication needed for securing the session, based on the
policies.
Static tunnels are created when the TSP negotiation is terminated.
Static tunnels are not open gateways and exhibit less security issues
than automated tunnels. Static IPv6 in IPv4 tunnels security
considerations are described in [RFC2893].
9. Conclusion
The Tunnel Setup Protocol (TSP) is applicable in many environments,
such as: providers, enterprises, wireless, unmanaged networks, mobile
hosts and networks. TSP gives the two tunnel end-points the ability
to negotiate tunnel parameters, as well as prefix assignment, dns
delegation and routing in an authenticated session. It also provides
IPv4 NAT discovery function by using the most effective
encapsulation. It also supports the IPv4 mobility of the nodes.
10. Acknowledgements
This draft is the merge of many previous drafts about TSP. Octavio
Medina has contributed to an earlier draft (IPv4 in IPv6). Thanks to
the following people for comments on improving and clarifying this
document: Pekka Savola, Alan Ford, Jeroen Massar and Jean-Francois
Tremblay.
11. References
11.1 Normative References
[RFC2222] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.
[RFC2463] Conta, A. and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 2463, December 1998.
[RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", RFC 2831, May 2000.
[RFC2893] Gilligan, R. and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 2893, August 2000.
[W3C.REC-xml-1998]
Bray, T., Paoli, J., and C. Sperberg-McQueen, "Extensible
Markup Language (XML) 1.0", W3C REC-xml-1998,
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February 1998,
.
11.2 Informative References
[FJ93] Floyd, S. and V. Jacobson, "The Synchronization of
Periodic Routing Messages", Proceedings of ACM SIGCOMM
'93, September 1993.
[I-D.ietf-ngtrans-dstm]
Bound, J., "Dual Stack Transition Mechanism (DSTM)",
draft-ietf-ngtrans-dstm-08 (work in progress), July 2002.
[I-D.ietf-v6ops-3gpp-cases]
Soininen, J., "Transition Scenarios for 3GPP Networks",
draft-ietf-v6ops-3gpp-cases-03 (work in progress),
April 2003.
[I-D.ietf-v6ops-isp-scenarios-analysis]
Lind, M., Ksinant, V., Park, S., Baudot, A., and P.
Savola, "Scenarios and Analysis for Introducing IPv6 into
ISP Networks", draft-ietf-v6ops-isp-scenarios-analysis-03
(work in progress), June 2004.
[I-D.ietf-v6ops-unmaneval]
Huitema, C., "Evaluation of Transition Mechanisms for
Unmanaged Networks", draft-ietf-v6ops-unmaneval-03 (work
in progress), June 2004.
[RFC3053] Durand, A., Fasano, P., Guardini, I., and D. Lento, "IPv6
Tunnel Broker", RFC 3053, January 2001.
[UNP] Stevens, R., Fenner, B., and A. Rudoff, "Unix Network
Programming, 3rd edition", Addison Wesley ISBN 0-13-
141155-1, 2004.
Authors' Addresses
Marc Blanchet
Hexago
2875 boul. Laurier, suite 300
Sainte-Foy, QC G1V 2M2
Canada
Phone: +1 418 266 5533
Email: Marc.Blanchet@hexago.com
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Florent Parent
Hexago
2875 boul. Laurier, suite 300
Sainte-Foy, QC G1V 2M2
Canada
Phone: +1 418 266 5533
Email: Florent.Parent@hexago.com
Appendix A. The TSP DTD
]>
Figure 21
Appendix B. Error codes
Error codes are sent as a numeric value followed by a text message
describing the code. The Tunnel Setup Protocol defines error code
numbers 1 through 499 and 1000 through 1499. Profile dependant error
codes are defined within the 500 through 999 and 1500 through 1999
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range.
The predefined values are :
200 Success: Successful operation
300 Authentication failed: Invalid userid, password or authentication
mechanism.
301 No more tunnels available: The server has reached its capacity
limit.
302 Unsupported client version: The client version is not supported
by the server.
303 Unsupported tunnel type: The server does not provide the
requested tunnel type.
310 Server side error: Undefined server error
500 Invalid request format or specified length: Received request has
invalid syntax or truncated
501 Invalid IP address: IP address specified by the client is invalid
502 Invalid or duplicate nicname
504 Router function not supported
506 IPv4 prefix already used for existing tunnel
507 Requested prefix length cannot be assigned
509 DNS delegation setup error
514 Protocol error
517 Unsupported router protocol
518 Unsupported prefix length
520 Missing prefix length
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