| Internet Engineering Task Force | C. Zhou |
| Internet-Draft | Huawei Technologies |
| Intended status: Standards Track | T. Taylor |
| Expires: March 27, 2015 | PT Taylor Consulting |
| Q. Sun | |
| China Telecom | |
| M. Boucadair | |
| France Telecom | |
| September 23, 2014 |
Attribute-Value Pairs For Provisioning Customer Equipment Supporting IPv4-Over-IPv6 Transitional Solutions
draft-zhou-dime-4over6-provisioning-05
During the transition from IPv4 to IPv6, customer equipment may have to support one of the various transition methods that have been defined for carrying IPv4 packets over IPv6. This document enumerates the information that needs to be provisioned on a customer edge router to support a list of transition techniques based on tunneling IPv4 in IPv6, with a view to defining reusable components for a reasonable transition path between these techniques. To the extent that the provisioning is done dynamically, AAA support is needed to provide the information to the network server responsible for passing the information to the customer equipment. This document specifies Diameter (RFC 6733) attribute-value pairs to be used for that purpose.
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A number of transition technologies have been defined to allow IPv4 packets to pass between hosts and IPv4 networks over an intervening IPv6 network while minimizing the number of public IPv4 addresses that need to be consumed by the hosts. Different operators will deploy different technologies, and sometimes one operator will use more than one technology, depending on what is supported by the available equipment and upon other factors both technical and economic.
Each technique requires the provisioning of some subscriber-specific information on the customer edge device. The provisioning may be by DHCPv6 [RFC3315] or by some other method. This document is indifferent to the specific provisioning technique used, but assumes a deployment in which that information is managed by AAA (Authentication, Authorization, and Accounting) servers. It further assumes that this information is delivered to intermediate network nodes for onward provisioning using the Diameter protocol [RFC6733].
As described below, in the particular case where the Light Weight IPv4 Over IPv6 (LW4o6) [I-D.ietf-softwire-lw4over6] transition method has been deployed, per-subscriber-site information almost identical to that passed to the subscriber site [I-D.ietf-softwire-map-dhcp] or collected from it [I-D.fsc-softwire-dhcp4o6-saddr-opt] also needs to be delivered to the border router serving that site. The Diameter protocol may be used for this purpose too.
This document analyzes the information required to configure the customer edge equipment for the following set of transition methods:
[I-D.softwire-dslite-multicast] specifies a generic solution for delivery of IPv4 multicast services to IPv4 clients over an IPv6 multicast network. The solution was developed with DS-Lite in mind but it is however not limited to DS-Lite. As such, it applies also for LW4over6 and MAP-E. This document analyzes the information required to configure the customer edge equipment for the support of multicast in the context of DS-Lite, MAP, and LW4over6 in particular.
On the basis of those analyses it specifies a number of attribute-value pairs (AVPs) to allow the necessary subscriber-site-specific configuration information to be carried in Diameter.
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].
The abbreviation "CE" denotes the equipment at the customer edge that terminates the customer end of an IPv6 transitional tunnel. This will usually be a router, but could be a host directly connected to the network.
The term "tunnel source address" is used to denote the IPv6 source address used in the outer header of packets sent from the CE through an LW4over6 transitional tunnel to the border router.
This section reviews the parameters that need to be provisioned for each of the transition methods listed above. This enumeration provides the justification for the AVPs defined in the next section.
A means is required to indicate which transition method(s) a given subscriber is allowed to use. The approach taken in this document is to specify grouped AVPs specific to LW4over6 and MAP-E. The operator can control which of these two transition methods a given subscriber uses by ensuring that AAA passes only the grouped AVP relevant to that method. A grouped AVP is unnecessary for Dual-Stack Lite, since (as the next section indicates) AAA has to provide only one parameter. Hence the absence of either of the grouped AVPs indicates that the subscriber equipment will use Dual-Stack Lite. Provisioning of multicast is an orthogonal activity, since it is independent of the transition method.
DS-Lite is documented in [RFC6333]. The Basic Bridging BroadBand (B4) element at the customer premises needs to be provisioned with the IPv6 address of the AFTR (border router). Optionally, it could also be configured with the IPv4 address of the B4 interface facing the tunnel, where the default value in the absence of provisioning is 192.0.0.2 and valid values are 192.0.0.2 through 192.0.0.7. Provisioning this information through AAA is problematic because it is most likely used in a case where multiple B4 instances occupy the same device. This document therefore assumes that the B4 interface address is determined by other means (implementation-dependent or static assignment).
Light Weight IPv4 Over IPv6 (LW4over6) is documented in [I-D.ietf-softwire-lw4over6]. LW4over6 requires four items to be provisioned to the customer equipment:
As discussed in Section 4 of [I-D.ietf-softwire-lw4over6], it is necessary to synchronize this configuration with corresponding per-subscriber configuration at the border router. The border router information consists of the same public IPv4 address and port set parameters that are passed to the CE, bound together with the full /128 IPv6 address (not just the Binding Prefix) configured as the tunnel source address at the CE.
[I-D.fsc-softwire-dhcp4o6-saddr-opt] proposes a means whereby a DHCPv6 server can influence the choice of this address and collect it from the CE. Depending on the provisioning architecture deployed in a given network, it is possible that the tunnel source address is passed to AAA as an intermediate step before the binding information is passed on to the border router.
When an external IPv4 address is shared, LW4over6 and MAP-E restrict the CE to use of a subset of all available ports on the external side. Both transition methods use the the algorithm defined in Appendix B of [I-D.ietf-softwire-map] to derive the values of the port numbers in the port set. This algorithm features three parameters, describing the positioning and value of the Port Set Identifier (PSID) within each port number of the generated set:
Mapping of Address and Port with Encapsulation (MAP-E) is described in [I-D.ietf-softwire-map]. MAP-E requires the provisioning of the following per-subscriber information at the customer edge device:
As indicated in Section 5, bullet 1 of the MAP-E document, a MAP CE can be provisioned with multiple End-user IPv6 prefixes, each associated with its own Basic Mapping Rule. This does not change the basic requirement for representation of the corresponding information in the form of Diameter AVPs, but adds a potential requirement for multiple instances of this information to be present in the Diameter message, differing in the value of the End-user IPv6 prefix (in contrast to the Forward Mapping Rule instances).
The border router needs to be configured with the superset of the Mapping Rules passed to the customer sites it serves. Since this requirement does not require direct coordination with CE configuration in the way LW4over6 does, it is out of scope of the present document. However, the AVPs defined here may be useful if a separate Diameter application is used to configure the border router.
[I-D.softwire-dslite-multicast] specifies a generic solution for delivery of IPv4 multicast services to IPv4 clients over an IPv6 multicast network. The solution can be in particular deployed in a DS-Lite context, but is also adaptable to LW4over6 and MAP-E. [I-D.ietf-softwire-multicast-prefix-option] specifies how DHCPv6 [RFC3315] can be used to provision multicast-related information, particularly:
It appears that two items are common to the different transition methods and the corresponding AVPs to carry them can be reused:
[RFC6519] sets a precedent for representation of the IPv6 address of a border router as an FQDN. This can be dereferenced to one or more IP addresses by the provisioning system before being passed to the customer equipment, or left as an FQDN as it as in [RFC6334].
The remaining requirements are transition-method-specific:
This section provides the specifications for the AVPs needed to meet the requirements summarized in Section 2.6. Within the context of their usage, all of these AVPs MUST have the M bit set and the V bit cleared.
The IP-Prefix-Length AVP (AVP code TBD00) is of type Unsignedint. It provides the length of an IPv4 or IPv6 prefix. Valid values are from 0 to 32 for IPv4, and from 0 to 128 for IPv6. Tighter limits are given below for particular contexts of use of this AVP.
Following on the precedent set by [RFC6334] and [RFC6519], this document identifies a border router using an FQDN rather than an address. The Border-Router-Name AVP (AVP Code TBD01) is of type OctetString. The rules for encoding the FQDN are the same as those for the FQDN variant of the derived type DiameterIdentity (Section 4.3.1 of [RFC6733]).
The 64-Multicast-Attributes AVP (AVP Code TBD02) is of type Grouped. It contains the multicast-related prefixes needed for providing IPv4 multicast over IPv6 using DS-Lite, MAP-E, or LW4over6, as specified in [I-D.softwire-dslite-multicast].
The syntax is shown in Figure 1.
64-Multicast-Attributes ::= < AVP Header: TBD02 >
[ ASM-Prefix64 ]
[ SSM-Prefix64 ]
[ Delegated-IPv6-Prefix ]
*[ AVP ]
Figure 1: 64-Multicast-Attributes AVP
If either ASM-Prefix64 or SSM-Prefix64 or both are present, Delegated-IPv6-Prefix MUST also be present.
The ASM-Prefix64 AVP (AVP Code TBD03) conveys the value of ASM_mPrefix64 as identified in Section 2.1 and specified in [I-D.softwire-dslite-multicast]. The ASM-Prefix64 AVP is of type Grouped, as shown in Figure 2.
ASM-Prefix64 ::= < AVP Header: TBD03 >
{ IP-Address }
{ IP-Prefix-Length }
*[ AVP ]
Figure 2: ASM-Prefix64 AVP
IP-Address (AVP code 518) is defined in [RFC5777] and is of type Address. Within the ASM-Prefix64 AVP, it provides the value of an IPv6 prefix. The AddressType field in IP-Address MUST have value 2 (IPv6). The conveyed multicast IPv6 prefix MUST belong to the ASM range. Unused bits in IP-Address beyond the actual prefix MUST be set to zeroes by the sender and ignored by the receiver.
The IP-Prefix-Length AVP provides the actual length of the prefix contained in the IP-Address AVP. Within the ASM-Prefix64 AVP, valid values of the IP-Prefix-Length AVP are from 24 to 96.
The SSM-Prefix64 AVP (AVP Code TBD04) conveys the value of SSM_mPrefix64 as identified in Section 2.1 and specified in [I-D.softwire-dslite-multicast]. The SSM-Prefix64 AVP is of type Grouped, as shown in Figure 3.
SSM-Prefix64 ::= < AVP Header: TBD04 >
{ IP-Address }
{ IP-Prefix-Length }
*[ AVP ]
Figure 3: SSM-Prefix64 AVP
IP-Address (AVP code 518) provides the value of an IPv6 prefix. The AddressType field in IP-Address MUST have value 2 (IPv6). The conveyed multicast IPv6 prefix MUST belong to the SSM range. Unused bits in IP-Address beyond the actual prefix MUST be set to zeroes by the sender and ignored by the receiver.
The IP-Prefix-Length AVP provides the actual length of the prefix contained in the IP-Address AVP. With regard to prefix length, note that Section 6 of [RFC3306] requires that bits 33-95 of an SSM address in the FF3x range be set to zero, meaning that the prefix length for an SSM prefix is effectively 96. However, Section 1 of [RFC4607] suggests that the lower limit of 32 bits be preserved to allow potential future use of bits 33-95. Hence applications SHOULD accept prefix lengths between 32 and 96 inclusive.
Within the 64-Multicast-Attributes AVP, the Delegated-IPv6-Prefix AVP (AVP Code 123) conveys the value of uPrefix64, a unicast IPv6 prefix, as identified in Section 2.1 and specified in [I-D.softwire-dslite-multicast]. The Delegated-IPv6-Prefix AVP is defined in [RFC4818]. As specified by [RFC6052], the value in the Prefix-Length field MUST be one of 32, 48, 56, 64 or 96.
The Tunnel-Source-Pref-Or-Addr AVP (AVP Code TBD05) conveys either the IPv6 Binding Prefix or the tunnel source address on the CE, as described in Section 2.2. The Tunnel-Source-Pref-Or-Addr AVP is of type Grouped, with syntax as shown in Figure 4. One of the Delegated-IPv6-Prefix AVP or the Tunnel-Source-IPv6-Address AVP MUST be present.
Tunnel-Source-Pref-Or-Addr ::= < AVP Header: TBD05 >
[ Delegated-IPv6-Prefix ]
[ Tunnel-Source-IPv6-Address ]
*[ AVP ]
Figure 4: Tunnel-Source-Pref-Or-Addr AVP
This AVP is defined separately from the LW4over6-Binding AVP (which includes it) to provide flexibility in the transport of the tunnel source address from the provisioning system to AAA while also supporting the provision of a complete binding to the LW4over6 border router.
The Delegated-IPv6-Prefix AVP (AVP code 123) is of type Octetstring, and is defined in [RFC4818]. Within the Tunnel-Source-Pref-Or-Addr AVP, it conveys the IPv6 Binding Prefix assigned to the CE. Valid values in the Prefix-Length field are from 0 to 128 (full address), although a more restricted range is obviously more reasonable.
The Tunnel-Source-IPv6-Address AVP (AVP code TBD06) is of type Address. It provides the address that the CE has assigned to its end of an LW4over6 tunnel. The AddressType field in this AVP MUST be set to 2 (IPv6). The DHCP 4o6 server described in [I-D.fsc-softwire-dhcp4o6-saddr-opt] can use the Tunnel-Source-IPv6-Address AVP to report the address to AAA after Step 3 of the binding flow shown in Section 4 of that document.
The Port-Set-Identifier AVP (AVP Code TBD07) is a structured OctetString with four octets of data, hence a total AVP length of 12. The description of the structure which follows refers to refers to the parameters described in Section 2.3.
The LW4over6-Binding AVP (AVP Code TBD08) is of type Grouped. It contains the elements of configuration that constitute the binding between an LW4over6 tunnel and IPv4 packets sent through that tunnel, as described in Section 2.2.
LW4over6-Binding ::= < AVP Header: TBD08 >
{ Tunnel-Source-Pref-Or-Addr }
{ LW4over6-External-IPv4-Addr }
[ Port-Set-Identifier ]
*[ AVP ]
Figure 5
The Tunnel-Source-Pref-Or-Addr AVP is defined in Section 3.4 and provides either the Binding Prefix or the full IPv6 tunnel source address. This AVP MUST be present.
The LW4over6-External-IPv4-Addr AVP (AVP Code TBD09) uses the Address derived data format defined in Section 4.3.1 of [RFC6733]. It provides the CE's external IPv4 address within the LW4over6 tunnel associated with the given binding. The AddressType field MUST be set to 1 (IPv4), and the total length of the AVP MUST be 14 octets. This AVP MUST be present.
The Port-Set-Identifier AVP is defined in Section 3.5. It identifies the specific set of ports assigned to the LW4over6 tunnel, when the IPv4 address is being shared.
The MAP-E-Attributes AVP (AVP Code TBD10) is of type Grouped. It contains the configuration data identified in Section 2.4 for all of the mapping rules (Basic and Forwarding) in a single MAP domain. Multiple instances of this AVP will be present if the CE belongs to multiple MAP domains.
MAP-E-Attributes ::= < AVP Header: TBD06 >
1*{ Border-Router-Name }
1*{ MAP-Mapping-Rule }
[ MAP-Mesh-Mode ]
[ Delegated-IPv6-Prefix ]
*[ AVP ]
Figure 6
The Border-Router-Name AVP is defined in Section 3.2. It provides the FQDN of a MAP border relay at the edge of the MAP domain to which the containing MAP-E-Attributes AVP relates. At least one instance of this AVP MUST be present.
The MAP-Mapping-Rule AVP is defined in Section 3.8. At least one instance of this AVP MUST be present. If the MAP-E domain supports mesh mode (indicated by the presence of the MAP-Mesh-Mode AVP), additional MAP-Mapping-Rule instances MAY be present. If the MAP-E domain is operating in hub-and-spoke mode, additional MAP-Mapping-Rule instances MUST NOT be present.
The MAP-Mesh-Mode AVP (AVP Code TBD11) uses the OctetString data format but has no data. Hence the AVP length is always 8. The absence of the mesh mode indicator attribute indicates that the CE is required to operate in hub-and-spoke mode.
The Delegated-IPv6-Prefix AVP (AVP Code 123) provides the End-user IPv6 prefix assigned to the CE for the MAP domain to which the containing MAP-E-Attributes AVP relates. The AVP is defined in [RFC4818]. Valid values of the Prefix-Length field range from 0 to 128.
The Delegated-IPv6-Prefix AVP is optional because, depending on deployment, the End-user IPv6 prefix may be provided by AAA or by other means. If multiple instances of the MAP-E-Attributes AVP containing the Delegated-IPv6-Prefix AVP are present, each instance of the latter MUST have a different value.
The MAP-Mapping-Rule AVP (AVP Code TBD12) is of type Grouped, and is used only in conjunction with MAP-based transition methods. Mapping rules are required both by the MAP border relay and by the CE. The components of the MAP-Mapping-Rule AVP provide the contents of a mapping rule as described in Section 2.4.
The syntax of the MAP-Mapping-Rule AVP is as follows:
MAP-Mapping-Rule ::= < AVP Header: TBD12 >
{ Rule-IPv4-Addr-Or-Prefix }
{ Rule-IPv6-Prefix }
{ EA-Field-Length }
{ Port-Set-Identifier }
*[ AVP ]
Figure 7
The Rule-IPv4-Addr-Or-Prefix, Rule-IPv6-Prefix, EA-Field-Length, and Port-Set-Identifier AVPs MUST all be present.
The Rule-IPv4-Addr-Or-Prefix AVP (AVP Code TBD13) conveys the rule IPv4 prefix and length as described in Section 2.4. The Rule-IPv4-Addr-Or-Prefix AVP is of type Grouped, as shown in Figure 8.
Rule-IPv4-Addr-Or-Prefix ::= < AVP Header: TBD13 >
{ IP-Address }
{ IP-Prefix-Length }
*[ AVP ]
Figure 8: Rule-IPv4-Addr-Or-Prefix AVP
IP-Address (AVP code 518) is defined in [RFC5777] and is of type Address. Within the Rule-IPv4-Addr-Or-Prefix AVP, it provides the value of a unicast IPv4 address or prefix. The AddressType field in IP-Address MUST have value 1 (IPv4). Unused bits in IP-Address beyond the actual prefix MUST be set to zeroes by the sender and ignored by the receiver.
The IP-Prefix-Length AVP provides the actual length of the prefix contained in the IP-Address AVP. Within the Rule-IPv4-Addr-Or-Prefix AVP, valid values of the IP-Prefix-Length AVP are from 0 to 32 (full address), based on the different cases identified in Section 5.2 of [I-D.ietf-softwire-map].
The Rule-IPv6-Prefix AVP (AVP Code TBD14) conveys the rule IPv6 prefix and length as described in Section 2.4. The Rule-IPv6-Prefix AVP is of type Grouped, as shown in Figure 9.
Rule-IPv6-Prefix ::= < AVP Header: TBD14 >
{ IP-Address }
{ IP-Prefix-Length }
*[ AVP ]
Figure 9: Rule-IPv6-Prefix AVP
IP-Address (AVP code 518) is defined in [RFC5777] and is of type Address. Within the Rule-IPv6-Prefix AVP, it provides the value of a unicast IPv6 prefix. The AddressType field in IP- Address MUST have value 2 (IPv6). Unused bits in IP-Address beyond the actual prefix MUST be set to zeroes by the sender and ignored by the receiver. This AVP MUST be present.
The IP-Prefix-Length AVP provides the actual length of the prefix contained in the IP-Address AVP. Within the Rule-IPv6-Prefix AVP, the minimum valid prefix length is 0. The maximum value is bounded by the length of the End-user IPv6 prefix associated with the mapping rule, if present in the form of the Delegated-IPv6-Prefix AVP in the enclosing MAP-E-Attributes AVP. Otherwise the maximum value is 128. This AVP MUST be present.
The EA-Field-Length AVP (AVP Code TBD15) is of type Unsigned32. Valid values range from 0 to 48. See Section 5.2 of [I-D.ietf-softwire-map] for a description of the use of this parameter in deriving IPv4 address and port number configuration. This AVP MUST be present.
The Port-Set-Identifier AVP provides information to identify the specific set of ports assigned to the CE. For more information see Section 2.4 and Section 2.3. The Port-Set-Identifier AVP is defined in Section 3.5. It MUST be present.
Huawei Technologies funded Tom Taylor's work on earlier versions of this document.
This memo requests to IANA to register the following Diameter AVP codes:
| Code | Attribute Name | Reference |
|---|---|---|
| TBD00 | IP-Prefix-Length | This document |
| TBD01 | Border-Router-Name | This document |
| TBD02 | 64-Multicast-Attributes | This document |
| TBD03 | ASM-Prefix64 | This document |
| TBD04 | SSM-Prefix64 | This document |
| TBD05 | Tunnel-Source-Pref-Or-Addr | This document |
| TBD06 | Tunnel-Source-IPv6-Address | This document |
| TBD07 | Port-Set-Identifier | This document |
| TBD08 | LW4over6-Binding | This document |
| TBD09 | LW4over6-External-IPv4-Addr | This document |
| TBD10 | MAP-E-Attributes | This document |
| TBD11 | MAP-Mesh-Mode | This document |
| TBD12 | MAP-Mapping-Rule | This document |
| TBD13 | Rule-IPv4-Addr-Or-Prefix | This document |
| TBD14 | Rule-IPv6-Prefix | This document |
| TBD15 | EA-Field-Length | This document |
The AVPs defined in this document face two threats, both dependent on man-in-the-middle attacks on the Diameter delivery path. The more serious threat is denial of service through modification of the AVP contents leading to misconfiguration. The lesser threat is disclosure of subscriber addresses allowing the attacker to track subscriber activity.
Diameter security is currently provided on a hop-by-hop basis (see Section 2.2 of [RFC6733]). The Diameter end-to-end security problem has not been solved, so man-in-the-middle attacks on Diameter peers along the path are possible. The present document does not propose to solve that general problem, but simply warn that it exists.