Internet Engineering Task Force (IETF) D. Cheng
Request for Comments: 8045 Huawei
Category: Standards Track J. Korhonen
ISSN: 2070-1721 Broadcom Corporation
M. Boucadair
Orange
S. Sivakumar
Cisco Systems
January 2017
RADIUS Extensions for IP Port Configuration and Reporting
Abstract
This document defines three new RADIUS attributes. For devices that
implement IP port ranges, these attributes are used to communicate
with a RADIUS server in order to configure and report IP transport
ports as well as mapping behavior for specific hosts. This mechanism
can be used in various deployment scenarios such as Carrier-Grade
NAT, IPv4/IPv6 translators, Provider WLAN gateway, etc. This
document defines a mapping between some RADIUS attributes and IP Flow
Information Export (IPFIX) Information Element identifiers.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8045.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. Extensions of RADIUS Attributes and TLVs . . . . . . . . . . 5
3.1. Extended Attributes for IP Ports . . . . . . . . . . . . 6
3.1.1. IP-Port-Limit-Info Attribute . . . . . . . . . . . . 6
3.1.2. IP-Port-Range Attribute . . . . . . . . . . . . . . . 8
3.1.3. IP-Port-Forwarding-Map Attribute . . . . . . . . . . 11
3.2. RADIUS TLVs for IP Ports . . . . . . . . . . . . . . . . 13
3.2.1. IP-Port-Type TLV . . . . . . . . . . . . . . . . . . 14
3.2.2. IP-Port-Limit TLV . . . . . . . . . . . . . . . . . . 15
3.2.3. IP-Port-Ext-IPv4-Addr TLV . . . . . . . . . . . . . . 15
3.2.4. IP-Port-Int-IPv4-Addr TLV . . . . . . . . . . . . . . 16
3.2.5. IP-Port-Int-IPv6-Addr TLV . . . . . . . . . . . . . . 17
3.2.6. IP-Port-Int-Port TLV . . . . . . . . . . . . . . . . 18
3.2.7. IP-Port-Ext-Port TLV . . . . . . . . . . . . . . . . 19
3.2.8. IP-Port-Alloc TLV . . . . . . . . . . . . . . . . . . 20
3.2.9. IP-Port-Range-Start TLV . . . . . . . . . . . . . . . 21
3.2.10. IP-Port-Range-End TLV . . . . . . . . . . . . . . . . 22
3.2.11. IP-Port-Local-Id TLV . . . . . . . . . . . . . . . . 22
4. Applications, Use Cases, and Examples . . . . . . . . . . . . 24 23
4.1. Managing CGN Port Behavior Using RADIUS . . . . . . . . . 24
4.1.1. Configure IP Port Limit for a User . . . . . . . . . 24
4.1.2. Report IP Port Allocation/Deallocation . . . . . . . 26
4.1.3. Configure Forwarding Port Forwarding Mapping . . . . . . . . . . 28
4.1.4. An Example . . . . . . . . . . . . . . . . . . . . . 30
4.2. Report Assigned Port Set for a Visiting UE . . . . . . . 31
5. Table of Attributes . . . . . . . . . . . . . . . . . . . . . 32
6. Security Considerations . . . . . . . . . . . . . . . . . . . 33
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
7.1. New IPFIX Information Elements . . . . . . . . . . . . . 34
7.2. New RADIUS Attributes . . . . . . . . . . . . . . . . . . 34
7.3. New RADIUS TLVs . . . . . . . . . . . . . . . . . . . . . 35
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.1. Normative References . . . . . . . . . . . . . . . . . . 35
8.2. Informative References . . . . . . . . . . . . . . . . . 36
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
In a broadband network, customer information is usually stored on a
RADIUS server [RFC2865]. At the time when a user initiates an IP
connection request, if this request is authorized, the RADIUS server
will populate the user's configuration information to the Network
Access Server (NAS), which is often referred to as a Broadband
Network Gateway (BNG) in broadband access networks. The Carrier-
Grade NAT (CGN) function may also be implemented on the BNG. Within
this document, the CGN may perform Network Address Translation from
IPv4 Clients to IPv4 Servers (NAT44) [RFC3022], NAT from IPv6 Clients
to IPv4 Servers (NAT64) [RFC6146], or Dual-Stack Lite Address Family
Transition Router (AFTR) [RFC6333] function. In such case, the CGN
IP transport port (e.g., TCP/UDP port) mapping behaviors can be part
of the configuration information sent from the RADIUS server to the
NAS/BNG. The As part of the accounting information sent from the NAS/BNG
to a RADIUS server, the NAS/BNG may also report to the RADIUS server the IP port mapping
behavior applied by the CGN to a user session to the
RADIUS server, as part of the accounting information sent from the
NAS/BNG to a RADIUS server. session.
When IP packets traverse the CGN, it performs mapping on the IP
transport (e.g., TCP/UDP) source port as required. An IP transport
source port, along with a source IP address, destination IP address,
destination port, and protocol identifier, if applicable, uniquely
identify a mapping. Since the number space of IP transport ports in
the CGN's external realm is shared among multiple users assigned with
the same IPv4 address, the total number of a user's simultaneous IP
mappings is likely to be subject to a port quota (see Section 5 of
[RFC6269]).
The attributes defined in this document may also be used to report
the assigned port range in some deployments, such as Provider WLAN
[WIFI-SERVICES]. For example, a visiting host can be managed by
Customer Premises Equipment (CPE), which will need to report the
assigned port range to the service platform. This is required for
identification purposes (see TR-146 [TR-146] for more details).
This document proposes three new attributes as RADIUS protocol
extensions; they are used for separate purposes, as follows:
1. IP-Port-Limit-Info: This attribute may be carried in a RADIUS
Access-Accept, Access-Request, Accounting-Request, or CoA-Request
packet. The purpose of this attribute is to limit the total
number of IP source transport ports allocated to a user and
associated with one or more IPv4 or IPv6 addresses.
2. IP-Port-Range: This attribute may be carried in a RADIUS
Accounting-Request packet. The purpose of this attribute is for
an address-sharing device (e.g., a CGN) to report to the RADIUS
server the range of IP source transport ports that have been
allocated or deallocated for a user. The port range is bound to
an external IPv4 address.
3. IP-Port-Forwarding-Map: This attribute may be carried in RADIUS
Access-Accept, Access-Request, Accounting-Request, or CoA-Request
packet. The purpose of this attribute is to specify how an IP
internal source transport port, together with its internal IPv4
or IPv6 address, are mapped to an external source transport port
along with the external IPv4 address.
IPFIX Information Elements [RFC7012] can be used for IP flow
identification and representation over RADIUS. This document
provides a mapping between some RADIUS TLVs and IPFIX Information
Element identifiers. A new IPFIX Information Element is defined by
this document (see Section 3.2.2).
IP protocol numbers (refer to [ProtocolNumbers]) can be used for
identification of IP transport protocols (e.g., TCP [RFC0793], UDP
[RFC0768], Datagram Congestion Control Protocol (DCCP) [RFC4340], and
Stream Control Transmission Protocol (SCTP) [RFC4960]) that are
associated with some RADIUS attributes.
This document focuses on IPv4 address sharing. Mechanisms for IPv6
prefix sharing (e.g., IPv6-to-IPv6 Network Prefix Translation
(NPTv6)) are out of scope.
2. Terminology
This document makes use of the following terms:
o IP Port: This refers to an IP transport port (e.g., a TCP port
number or UDP port number).
o IP Port Type: This refers to the IP transport protocol as
indicated by the IP transport protocol number. Refer to
[ProtocolNumbers].
o IP Port Limit: This denotes the maximum number of IP ports for a
specific (or all) IP transport protocol(s) that a device
supporting port ranges can use when performing port number
mappings for a specific user/host. Note that this limit is
usually associated with one or more IPv4/IPv6 addresses.
o IP Port Range: This specifies a set of contiguous IP ports
indicated by the lowest numerical number and the highest numerical
number, inclusively.
o Internal IP Address: This refers to the IP address that is used by
a host as a source IP address in an outbound IP packet sent
towards a device supporting port ranges in the internal realm.
The internal IP address may be IPv4 or IPv6.
o External IP Address: This refers to the IP address that is used as
a source IP address in an outbound IP packet after traversing a
device supporting port ranges in the external realm. This
document assumes that the external IP address is an IPv4 address.
o Internal Port: This is an IP transport port that is allocated by a
host or application behind an address-sharing device for an
outbound IP packet in the internal realm.
o External Port: This is an IP transport port that is allocated by
an address-sharing device upon receiving an outbound IP packet in
the internal realm and is used to replace the internal port that
is allocated by a user or application.
o External Realm: This refers to the networking segment where
external IP addresses are used as source addresses of outbound
packets forwarded by an address-sharing device.
o Internal Realm: This refers to the networking segment that is
behind an address-sharing device and where internal IP addresses
are used.
o Mapping: This denotes a relationship between an internal IP
address, internal port, and protocol, as well as an external IP
address, external port, and protocol.
o Address-Sharing Device: This is a device that is capable of
sharing an IPv4 address among multiple users. A typical example
of this device is a CGN, CPE, Provider WLAN gateway, etc.
2.1. Requirements Language
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 RFC 2119 [RFC2119].
3. Extensions of RADIUS Attributes and TLVs
These three new attributes are defined in the following subsections:
1. IP-Port-Limit-Info Attribute
2. IP-Port-Range Attribute
3. IP-Port-Forwarding-Map Attribute
All these attributes are allocated from the RADIUS "Extended Type"
code space per [RFC6929].
These attributes and their embedded TLVs (refer to Section 3.2) are
defined with globally unique names and follow the guidelines in
Section 2.7.1 of [RFC6929].
In all the figures describing the RADIUS attributes and TLV formats
in the following subsections, the fields are transmitted from left to
right.
3.1. Extended Attributes for IP Ports
3.1.1. IP-Port-Limit-Info Attribute
This attribute is of type "TLV" "tlv" as defined in the RADIUS Protocol
Extensions [RFC6929]. It contains some sub-attributes, and the
requirements are as follows:
o The IP-Port-Limit-Info Attribute MAY contain the IP-Port-Type TLV
(see Section 3.2.1).
o The IP-Port-Limit-Info Attribute MUST contain the IP-Port-Limit
TLV (see Section 3.2.2).
o The IP-Port-Limit-Info Attribute MAY contain the IP-Port-Ext-
IPv4-Addr TLV (see Section 3.2.3).
The IP-Port-Limit-Info Attribute specifies the maximum number of IP
ports, as indicated in IP-Port-Limit TLV, of a specific IP transport
protocol, as indicated in IP-Port-Type TLV, and associated with a
given IPv4 address, as indicated in IP-Port-Ext-IPv4-Addr TLV, for an
end user.
Note that when IP-Port-Type TLV is not included as part of the IP-
Port-Limit-Info Attribute, the port limit applies to all IP transport
protocols.
Note also that when IP-Port-Ext-IPv4-Addr TLV is not included as part
of the IP-Port-Limit-Info Attribute, the port limit applies to all
the IPv4 addresses managed by the address-sharing device, e.g., a CGN
or NAT64 device.
The IP-Port-Limit-Info Attribute MAY appear in an Access-Accept
packet. It MAY also appear in an Access-Request packet as a
preferred maximum number of IP ports indicated by the device
supporting port ranges co-located with the NAS, e.g., a CGN or NAT64.
The IP-Port-Limit-Info Attribute MAY appear in a CoA-Request packet.
The IP-Port-Limit-Info Attribute MAY appear in an Accounting-Request
packet.
The IP-Port-Limit-Info Attribute MUST NOT appear in any other RADIUS
packet.
The format of the IP-Port-Limit-Info Attribute is shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Extended-Type | Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
Type
241
Length
This field indicates the total length in bytes octets of all fields of
this attribute, including the Type, Length, Extended-Type, and the
entire length of the embedded TLVs.
Extended-Type
5
Value
This field contains a set of TLVs as follows:
IP-Port-Type TLV
This TLV contains a value that indicates the IP port type.
Refer to Section 3.2.1.
IP-Port-Limit TLV
This TLV contains the maximum number of IP ports of a specific
IP port type and associated with a given IPv4 address for an
end user. This TLV MUST be included in the IP-Port-Limit-Info
Attribute. Refer to Section 3.2.2. This limit applies to all
mappings that can be instantiated by an underlying address-
sharing device without soliciting any external entity. In
particular, this limit does not include the ports that are
instructed by an Authentication, Authorization, and Accounting
(AAA) server.
IP-Port-Ext-IPv4-Addr TLV
This TLV contains the IPv4 address that is associated with the
IP port limit contained in the IP-Port-Limit TLV. This TLV is
optionally included as part of the IP-Port-Limit-Info
Attribute. Refer to Section 3.2.3.
IP-Port-Limit-Info Attribute is associated with the following
identifier: 241.5.
3.1.2. IP-Port-Range Attribute
This attribute is of type "TLV" "tlv" as defined in the RADIUS Protocol
Extensions [RFC6929]. It contains some sub-attributes and the
requirement is as follows:
o The IP-Port-Range Attribute MAY contain the IP-Port-Type TLV (see
Section 3.2.1).
o The IP-Port-Range Attribute MUST contain the IP-Port-Alloc TLV
(see Section 3.2.8).
o For port allocation, the IP-Port-Range Attribute MUST contain both
the IP-Port-Range-Start TLV (see Section 3.2.9) and the IP-Port-
Range-END TLV (see Section 3.2.10). For port deallocation, the
IP-Port-Range Attribute MAY contain both of these two TLVs; if the
two TLVs are not included, it implies that all ports that were
previously allocated are now all deallocated.
o The IP-Port-Range Attribute MAY contain the IP-Port-Ext-IPv4-Addr
TLV (see Section 3.2.3).
o The IP-Port-Range Attribute MAY contain the IP-Port-Local-Id TLV
(see Section 3.2.11).
The IP-Port-Range Attribute contains a range of contiguous IP ports.
These ports are either to be allocated or deallocated depending on
the Value carried by the IP-Port-Alloc TLV.
If the IP-Port-Type TLV is included as part of the IP-Port-Range
Attribute, then the port range is associated with the specific IP
transport protocol as specified in the IP-Port-Type TLV, but
otherwise it is for all IP transport protocols.
If the IP-Port-Ext-IPv4-Addr TLV is included as part of the IP-Port-
Range Attribute, then the port range as specified is associated with
the IPv4 address as indicated, but otherwise it is for all IPv4
addresses by the address-sharing device (e.g., a CGN device) for the
end user.
This attribute can be used to convey a single IP transport port
number: in such case, the Value of the IP-Port-Range-Start TLV and
the IP-Port-Range-End TLV, respectively, contain the same port
number.
The information contained in the IP-Port-Range Attribute is sent to
RADIUS server.
The IP-Port-Range Attribute MAY appear in an Accounting-Request
packet.
The IP-Port-Range Attribute MUST NOT appear in any other RADIUS
packet.
The format of the IP-Port-Range Attribute is shown in Figure 2.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Extended-Type | Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
Type
241
Length
This field indicates the total length in bytes octets of all fields of
this attribute, including the Type, Length, Extended-Type, and the
entire length of the embedded TLVs.
Extended-Type
6
Value
This field contains a set of TLVs as follows:
IP-Port-Type TLV
This TLV contains a value that indicates the IP port type.
Refer to Section 3.2.1.
IP-Port-Alloc TLV
This TLV contains a flag to indicate the range of the specified
IP ports for either allocation or deallocation. This TLV MUST
be included as part of the IP-Port-Range Attribute. Refer to
Section 3.2.8.
IP-Port-Range-Start TLV
This TLV contains the smallest port number of a range of
contiguous IP ports. To report the port allocation, this TLV
MUST be included together with IP-Port-Range-End TLV as part of
the IP-Port-Range Attribute. Refer to Section 3.2.9.
IP-Port-Range-End TLV
This TLV contains the largest port number of a range of
contiguous IP ports. To report the port allocation, this TLV
MUST be included together with IP-Port-Range-Start TLV as part
of the IP-Port-Range Attribute. Refer to Section 3.2.10.
IP-Port-Ext-IPv4-Addr TLV
This TLV contains the IPv4 address that is associated with the
IP port range, as is collectively indicated in the IP-Port-
Range-Start TLV and the IP-Port-Range-End TLV. This TLV is
optionally included as part of the IP-Port-Range Attribute.
Refer to Section 3.2.3.
IP-Port-Local-Id TLV
This TLV contains a local session significant identifier at the
customer premise, such as the Media Access Control (MAC)
address, interface ID, VLAN ID, PPP sessions ID, VPN Routing
and Forwarding (VRF) ID, IP address/prefix, etc. This TLV is
optionally included as part of the IP-Port-Range Attribute.
Refer to Section 3.2.11.
The IP-Port-Range Attribute is associated with the following
identifier: 241.6.
3.1.3. IP-Port-Forwarding-Map Attribute
This attribute is of type "TLV" "tlv" as defined in the RADIUS Protocol
Extensions [RFC6929]. It contains some sub-attributes and the
requirement is as follows:
o The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-Type
TLV (see Section 3.2.1).
o The IP-Port-Forwarding-Map Attribute MUST contain both IP-Port-
Int-Port TLV (see Section 3.2.6) and the IP-Port-Ext-Port TLV (see
Section 3.2.7).
o If the internal realm is with an IPv4 address family, the IP-Port-
Forwarding-Map Attribute MUST contain the IP-Port-Int-IPv4-Addr
TLV (see Section 3.2.4); if the internal realm is with an IPv6
address family, the IP-Port-Forwarding-Map Attribute MUST contain
the IP-Port-Int-IPv6-Addr TLV (see Section 3.2.5).
o The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-Ext-
IPv4-Addr TLV (see Section 3.2.3).
o The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-
Local-Id TLV (see Section 3.2.11).
The attribute contains a 2-byte two-octet IP internal port number and a 2-byte two-
octet IP external port number. The internal port number is
associated with an internal IPv4 or IPv6 address that MUST always be
included. The external port number is associated with a specific
external IPv4 address if included, but otherwise it is associated
with all external IPv4 addresses for the end user.
If the IP-Port-Type TLV is included as part of the IP-Port-
Forwarding-Map Attribute, then the port mapping is associated with
the specific IP transport protocol as specified in the IP-Port-Type
TLV, but otherwise it is for all IP transport protocols.
The IP-Port-Forwarding-Map Attribute MAY appear in an Access-Accept
packet. It MAY also appear in an Access-Request packet to indicate a
preferred port mapping by the device co-located with NAS. However,
the server is not required to honor such a preference.
The IP-Port-Forwarding-Map Attribute MAY appear in a CoA-Request
packet.
The IP-Port-Forwarding-Map Attribute MAY also appear in an
Accounting-Request packet.
The IP-Port-Forwarding-Map Attribute MUST NOT appear in any other
RADIUS packet.
The format of the IP-Port-Forwarding-Map Attribute is shown in
Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Extended-Type | Value ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
Type
241
Length
This field indicates the total length in bytes octets of all fields of
this attribute, including the Type, Length, Extended-Type, and the
entire length of the embedded TLVs.
Extended-Type
7
Value
This field contains a set of TLVs as follows:
IP-Port-Type TLV
This TLV contains a value that indicates the IP port type.
Refer to Section 3.2.1.
IP-Port-Int-Port TLV
This TLV contains an internal IP port number associated with an
internal IPv4 or IPv6 address. This TLV MUST be included
together with IP-Port-Ext-Port TLV as part of the IP-Port-
Forwarding-Map Attribute. Refer to Section 3.2.6.
IP-Port-Ext-Port TLV
This TLV contains an external IP port number associated with an
external IPv4 address. This TLV MUST be included together with
IP-Port-Int-Port TLV as part of the IP-Port-Forwarding-Map
Attribute. Refer to Section 3.2.7.
IP-Port-Int-IPv4-Addr TLV
This TLV contains an IPv4 address that is associated with the
internal IP port number contained in the IP-Port-Int-Port TLV.
For the internal realm with an IPv4 address family, this TLV
MUST be included as part of the IP-Port-Forwarding-Map
Attribute. Refer to Section 3.2.4.
IP-Port-Int-IPv6-Addr TLV
This TLV contains an IPv6 address that is associated with the
internal IP port number contained in the IP-Port-Int-Port TLV.
For the internal realm with an IPv6 address family, this TLV
MUST be included as part of the IP-Port-Forwarding-Map
Attribute. Refer to Section 3.2.5.
IP-Port-Ext-IPv4-Addr TLV
This TLV contains an IPv4 address that is associated with the
external IP port number contained in the IP-Port-Ext-Port TLV.
This TLV MAY be included as part of the IP-Port-Forwarding-Map
Attribute. Refer to Section 3.2.3.
IP-Port-Local-Id TLV
This TLV contains a local session significant identifier at the
customer premise, such as MAC address, interface ID, VLAN ID,
PPP sessions ID, VRF ID, IP address/prefix, etc. This TLV is
optionally included as part of the IP-Port-Forwarding-Map
Attribute. Refer to Section 3.2.11.
The IP-Port-Forwarding-Map Attribute is associated with the following
identifier: 241.7.
3.2. RADIUS TLVs for IP Ports
The TLVs that are included in the three attributes (see Section 3.1)
are defined in the following subsections. These TLVs use the format
defined in [RFC6929]. As the three attributes carry similar data, we
have defined a common set of TLVs that are used for all three
attributes. That is, the TLVs have the same name and number when
encapsulated in any one of the three parent attributes. See Sections
3.1.1, 3.1.2, and 3.1.3 for a list of which TLV is permitted within
which parent attribute.
The encoding of the Value field of these TLVs follows the
recommendation of [RFC6158]. In particular, IP-Port-Type, IP-Port-
Limit, IP-Port-Int-Port, IP-Port-Ext-Port, IP-Port-Alloc, IP-Port-
Range-Start, and IP-Port-Range-End TLVs are encoded in 32 bits as per
the recommendation in Appendix A.2.1 of [RFC6158].
3.2.1. IP-Port-Type TLV
The format of IP-Port-Type TLV is shown in Figure 4. This attribute
carries the IP transport protocol number defined by IANA (refer to
[ProtocolNumbers]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | Protocol-Number
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Protocol-Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4
TLV-Type
1
Length
6
Six octets
Protocol-Number
Integer. This field contains the data (unsigned8) of the protocol
number defined in [ProtocolNumbers], right justified, and the
unused bits in this field MUST be set to zero. Protocols that do
not use a port number (e.g., the Resource Reservation Protocol
(RSVP) or IP Encapsulating Security Payload (ESP)) MUST NOT be
included in the IP-Port-Type TLV.
IP-Port-Type TLV MAY be included in the following attributes:
o IP-Port-Limit-Info Attribute, identified as 241.5.1 (see
Section 3.1.1)
o IP-Port-Range Attribute, identified as 241.6.1 (see Section 3.1.2)
o IP-Port-Forwarding-Map Attribute, identified as 241.7.1 (see
Section 3.1.3)
When the IP-Port-Type TLV is included within a RADIUS attribute, the
associated attribute is applied to the IP transport protocol as
indicated by the Protocol-Number only, such as TCP, UDP, SCTP, DCCP,
etc.
3.2.2. IP-Port-Limit TLV
The format of IP-Port-Limit TLV is shown in Figure 5. This attribute
carries IPFIX Information Element "sourceTransportPortsLimit (458),
which indicates the maximum number of IP transport ports as a limit
for an end user to use that is associated with one or more IPv4 or
IPv6 addresses.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | sourceTransportPortsLimit
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceTransportPortsLimit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5
TLV-Type
2
Length
6
Six octets
sourceTransportPortsLimit
Integer. This field contains the data (unsigned16) of
sourceTransportPortsLimit (458) defined in IPFIX, right justified,
and the unused bits in this field MUST be set to zero.
IP-Port-Limit TLV MUST be included as part of the IP-Port-Limit-Info
Attribute (refer to Section 3.1.1), identified as 241.5.2.
3.2.3. IP-Port-Ext-IPv4-Addr TLV
The format of IP-Port-Ext-IPv4-Addr TLV is shown in Figure 6. This
attribute carries IPFIX Information Element 225,
"postNATSourceIPv4Address", which is the IPv4 source address after
NAT operation (refer to [IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | postNATSourceIPv4Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
postNATSourceIPv4Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6
TLV-Type
3
Length
6
Six octets
postNATSourceIPv4Address
Integer. This field contains the data (ipv4Address) of
postNATSourceIPv4Address (225) defined in IPFIX.
IP-Port-Ext-IPv4-Addr TLV MAY be included in the following
attributes:
o IP-Port-Limit-Info Attribute, identified as 241.5.3 (see
Section 3.1.1)
o IP-Port-Range Attribute, identified as 241.6.3 (see Section 3.1.2)
o IP-Port-Forwarding-Mapping Attribute, identified as 241.7.3 (see
Section 3.1.3)
3.2.4. IP-Port-Int-IPv4-Addr TLV
The format of IP-Port-Int-IPv4 TLV is shown in Figure 7. This
attribute carries IPFIX Information Element 8, "sourceIPv4Address",
which is the IPv4 source address before NAT operation (refer to
[IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | sourceIPv4Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceIPv4Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7
TLV-Type
4
Length
6
Six octets
sourceIPv4Address
Integer. This field contains the data (ipv4Address) of
sourceIPv4Address (8) defined in IPFIX.
If the internal realm is with an IPv4 address family, the IP-Port-
Int-IPv4-Addr TLV MUST be included as part of the IP-Port-Forwarding-
Map Attribute (refer to Section 3.1.3), identified as 241.7.4.
3.2.5. IP-Port-Int-IPv6-Addr TLV
The format of IP-Port-Int-IPv6-Addr TLV is shown in Figure 8. This
attribute carries IPFIX Information Element 27, "sourceIPv6Address",
which is the IPv6 source address before NAT operation (refer to
[IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | sourceIPv6Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceIPv6Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceIPv6Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceIPv6Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceIPv6Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8
TLV-Type
5
Length
18
Eighteen octets
sourceIPv6Address
IPv6 address (128 bits). This field contains the data
(ipv6Address) of sourceIPv6Address (27) defined in IPFIX.
If the internal realm is with an IPv6 address family, the IP-Port-
Int-IPv6-Addr TLV MUST be included as part of the IP-Port-Forwarding-
Map Attribute (refer to Section 3.1.3), identified as 241.7.5.
3.2.6. IP-Port-Int-Port TLV
The format of IP-Port-Int-Port TLV is shown in Figure 9. This
attribute carries IPFIX Information Element 7, "sourceTransportPort",
which is the source transport number associated with an internal IPv4
or IPv6 address (refer to [IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | sourceTransportPort
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sourceTransportPort |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9
TLV-Type
6
Length
6
Six octets
sourceTransportPort
Integer. This field contains the data (unsigned16) of
sourceTransportPort (7) defined in IPFIX, right justified, and
unused bits MUST be set to zero.
IP-Port-Int-Port TLV MUST be included as part of the IP-Port-
Forwarding-Map Attribute (refer to Section 3.1.3), identified as
241.7.6.
3.2.7. IP-Port-Ext-Port TLV
The format of IP-Port-Ext-Port TLV is shown in Figure 10. This
attribute carries IPFIX Information Element 227,
"postNAPTSourceTransportPort", which is the transport number
associated with an external IPv4 address (refer to [IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | postNAPTSourceTransportPort
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
postNAPTSourceTransportPort |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10
TLV-Type
7
Length
6
Six octets
postNAPTSourceTransportPort
Integer. This field contains the data (unsigned16) of
postNAPTSourceTransportPort (227) defined in IPFIX, right
justified, and unused bits MUST be set to zero.
IP-Port-Ext-Port TLV MUST be included as part of the IP-Port-
Forwarding-Map Attribute (refer to Section 3.1.3), identified as
241.7.7.
3.2.8. IP-Port-Alloc TLV
The format of IP-Port-Alloc TLV is shown in Figure 11. This
attribute carries IPFIX Information Element 230, "natEvent", which is
a flag to indicate an action of NAT operation (refer to [IPFIX]).
When the value of natEvent is "1" (Create event), it means to
allocate a range of transport ports; when the value is "2", it means
to deallocate a range of transports ports. For the purpose of this
TLV, no other value is used.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | natEvent
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
natEvent |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11
TLV-Type
8
Length
6
Six octets
natEvent
Integer. This field contains the data (unsigned8) of natEvent
(230) defined in IPFIX, right justified, and unused bits MUST be
set to zero. It indicates the allocation or deallocation of a
range of IP ports as follows:
0: Reserved
1: Allocation
2: Deallocation
Reserved:
0.
IP-Port-Alloc TLV MUST be included as part of the IP-Port-Range
Attribute (refer to Section 3.1.2), identified as 241.6.8.
3.2.9. IP-Port-Range-Start TLV
The format of IP-Port-Range-Start TLV is shown in Figure 12. This
attribute carries IPFIX Information Element 361, "portRangeStart",
which is the smallest port number of a range of contiguous transport
ports (refer to [IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | portRangeStart
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
portRangeStart |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12
TLV-Type
9
Length
6
Six octets
portRangeStart
Integer. This field contains the data (unsigned16) of
portRangeStart (361) defined in IPFIX, right justified, and unused
bits MUST be set to zero.
IP-Port-Range-Start TLV is included as part of the IP-Port-Range
Attribute (refer to Section 3.1.2), identified as 241.6.9.
3.2.10. IP-Port-Range-End TLV
The format of IP-Port-Range-End TLV is shown in Figure 13. This
attribute carries IPFIX Information Element 362, "portRangeEnd",
which is the largest port number of a range of contiguous transport
ports (refer to [IPFIX]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | portRangeEnd
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
portRangeEnd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13
TLV-Type
10
Length
6
Six octets
portRangeEnd
Integer. This field contains the data (unsigned16) of
portRangeEnd (362) defined in IPFIX, right justified, and unused
bits MUST be set to zero.
IP-Port-Range-End TLV is included as part of the IP-Port-Range
Attribute (refer to Section 3.1.2), identified as 241.6.10.
3.2.11. IP-Port-Local-Id TLV
The format of IP-Port-Local-Id TLV is shown in Figure 14. This
attribute carries a string called "localID", which is a local
significant identifier as explained below.
The primary issue addressed by this TLV is that there are CGN
deployments that do not distinguish internal hosts by their internal
IP address alone but use further identifiers for unique subscriber
identification. For example, this is the case if a CGN supports
overlapping private or shared IP address spaces (as described in
[RFC1918] and [RFC6598]) for internal hosts of different subscribers.
In such cases, different internal hosts are identified and mapped at
the CGN by their IP address and/or another identifier, for example,
the identifier of a tunnel between the CGN and the subscriber. In
these scenarios (and similar ones), the internal IP address is not
sufficient to demultiplex connections from internal hosts. An
additional identifier needs to be present in the IP-Port-Range
Attribute and IP-Port-Forwarding-Mapping Attribute in order to
uniquely identify an internal host. The IP-Port-Local-Id TLV is used
to carry this identifier.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV-Type | Length | localID ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14
TLV-Type
11
Length
Variable number of bytes octets
localID
String. The data type of this field is string (refer to
[RFC8044]). This field contains the data that is a local session
significant identifier at the customer premise, such as MAC
address, interface ID, VLAN ID, PPP sessions ID, VRF ID, IP
address/prefix, or another local session significant identifier.
IP-Port-Local-Id TLV MAY be included in the following Attributes if
it is necessary to identify the subscriber:
o IP-Port-Range Attribute, identified as 241.6.11 (see
Section 3.1.2)
o IP-Port-Forwarding-Mapping Attribute, identified as 241.7.11 (see
Section 3.1.3)
4. Applications, Use Cases, and Examples
This section describes some applications and use cases to illustrate
the use of the attributes proposed in this document.
4.1. Managing CGN Port Behavior Using RADIUS
In a broadband network, customer information is usually stored on a
RADIUS server, and the BNG acts as a NAS. The communication between
the NAS and the RADIUS server is triggered by a user when it signs in
to the Internet service where either PPP or DHCP/DHCPv6 is used.
When a user signs in, the NAS sends a RADIUS Access-Request message
to the RADIUS server. The RADIUS server validates the request, and
if the validation succeeds, it in turn sends back a RADIUS Access-
Accept message. The Access-Accept message carries configuration
information specific to that user back to the NAS, where some of the
information would be passed on to the requesting user via PPP or
DHCP/DHCPv6.
A CGN function in a broadband network is most likely to be co-located
on a BNG. In that case, parameters for CGN port mapping behavior for
users can be configured on the RADIUS server. When a user signs in
to the Internet service, the associated parameters can be conveyed to
the NAS, and proper configuration is accomplished on the CGN device
for that user.
Also, a CGN operation status such as CGN port allocation and
deallocation for a specific user on the BNG can also be transmitted
back to the RADIUS server for accounting purposes using the RADIUS
protocol.
The RADIUS protocol has already been widely deployed in broadband
networks to manage BNG, thus the functionality described in this
specification introduces little overhead to the existing network
operation.
In the following subsections, we describe how to manage CGN behavior
using the RADIUS protocol, with required RADIUS extensions proposed
in Section 3.
4.1.1. Configure IP Port Limit for a User
In the face of an IPv4 address shortage, there are currently
proposals to multiplex multiple users' connections over a number of
shared IPv4 addresses, such as Carrier Grade NAT [RFC6888], Dual-
Stack Lite [RFC6333], NAT64 [RFC6146], etc. As a result, a single
IPv4 public address may be shared by hundreds or even thousands of
users. As indicated in [RFC6269], it is therefore necessary to
impose limits on the total number of ports available to an individual
user to ensure that the shared resource, i.e., the IPv4 address,
remains available in some capacity to all the users using it. The
support of an IP port limit is also documented in [RFC6888] as a
requirement for CGN.
The IP port limit imposed on an end user may be on the total number
of IP source transport ports or a specific IP transport protocol as
defined in Section 3.1.1.
The per-user IP port limit is configured on a RADIUS server, along
with other user information such as credentials.
When a user signs in to the Internet service successfully, the IP
port limit for the subscriber is passed by the RADIUS server to the
BNG, which is acting as a NAS and is co-located with the CGN using
the IP-Port-Limit-Info RADIUS attribute (defined in Section 3.1.1)
along with other configuration parameters. While some parameters are
passed to the user, the IP port limit is recorded on the CGN device
for imposing the usage of IP transport ports for that user.
Figure 15 illustrates how the RADIUS protocol is used to configure
the maximum number of TCP/UDP ports for a given user on a CGN device.
User CGN/NAS AAA
| BNG Server
| | |
| | |
|----Service Request------>| |
| | |
| |-----Access-Request -------->|
| | |
| |<----Access-Accept-----------|
| | (IP-Port-Limit-Info) |
| | (for TCP/UDP ports) |
|<---Service Granted ------| |
| (other parameters) | |
| | |
| (CGN external port |
| allocation and |
| IPv4 address assignment) |
| | |
Figure 15: RADIUS Message Flow for Configuring CGN Port Limit
The IP port limit created on a CGN device for a specific user using a
RADIUS extension may be changed using a RADIUS CoA message [RFC5176]
that carries the same RADIUS attribute. The CoA message may be sent
from the RADIUS server directly to the NAS, and once a RADIUS CoA ACK
message is accepted and sent back, the new IP port limit replaces the
previous one.
Figure 16 illustrates how the RADIUS protocol is used to increase the
TCP/UDP port limit from 1024 to 2048 on a CGN device for a specific
user.
User CGN/NAS AAA
| BNG Server
| | |
| TCP/UDP Port Limit (1024) |
| | |
| |<---------CoA Request----------|
| | (IP-Port-Limit-Info) |
| | (for TCP/UDP ports) |
| | |
| TCP/UDP Port Limit (2048) |
| | |
| |---------CoA Response--------->|
| | |
Figure 16: RADIUS Message Flow for Changing a User's CGN Port Limit
4.1.2. Report IP Port Allocation/Deallocation
Upon obtaining the IP port limit for a user, the CGN device needs to
allocate an IP transport port for the user when receiving a new IP
flow sent from that user.
As one practice, a CGN may allocate a block of IP ports for a
specific user, instead of one port at a time, and within each port
block the ports may be randomly distributed or in consecutive
fashion. When a CGN device allocates a block of transport ports, the
information can be easily conveyed to the RADIUS server by a new
RADIUS attribute called the IP-Port-Range (defined in Section 3.1.2).
The CGN device may allocate one or more IP port ranges, where each
range contains a set of numbers representing IP transport ports and
the total number of ports MUST be less or equal to the associated IP
port limit imposed for that user. A CGN device may choose to
allocate a small port range and allocate more at a later time as
needed; such practice is good because of its randomization in nature.
At the same time, the CGN device also needs to decide on the shared
IPv4 address for that user. The shared IPv4 address and the pre-
allocated IP port range are both passed to the RADIUS server.
When a user initiates an IP flow, the CGN device randomly selects a
transport port number from the associated and pre-allocated IP port
range for that user to replace the original source port number along
with the replacement of the source IP address by the shared IPv4
address.
A CGN device may decide to "free" a previously assigned set of IP
ports that have been allocated for a specific user but are not
currently in use, and with that, the CGN device must send the
information of the deallocated IP port range along with the shared
IPv4 address to the RADIUS server.
Figure 17 illustrates how the RADIUS protocol is used to report a set
of ports allocated and deallocated, respectively, by a NAT64 device
for a specific user to the RADIUS server. 2001:db8:100:200::/56 is
the IPv6 prefix allocated to this user. In order to limit the usage
of the NAT64 resources on a per-user basis for fairness of resource
usage (see REQ-4 of [RFC6888]), port range allocations are bound to
the /56 prefix, not to the source IPv6 address of the request. The
NAT64 device is configured with the per-user port limit policy by
some means (e.g., subscriber-mask [RFC7785]).
Host NAT64/NAS AAA
| BNG Server
| | |
| | |
|----Service Request------>| |
| | |
| |-----Access-Request -------->|
| | |
| |<----Access-Accept-----------|
|<---Service Granted ------| |
| (other parameters) | |
... ... ...
| | |
| | |
| (NAT64 decides to allocate |
| a TCP/UDP port range for the user) |
| | |
| |-----Accounting-Request----->|
| | (IP-Port-Range |
| | for allocation) |
... ... ...
| | |
| (NAT64 decides to deallocate |
| a TCP/UDP port range for the user) |
| | |
| |-----Accounting-Request----->|
| | (IP-Port-Range |
| | for deallocation) |
| | |
Figure 17: RADIUS Message Flow for Reporting NAT64
Allocation/Deallocation of a Port Set
4.1.3. Configure Forwarding Port Forwarding Mapping
In most scenarios, the port mapping on a NAT device is dynamically
created when the IP packets of an IP connection initiated by a user
arrives. For some applications, the port mapping needs to be pre-
defined and allow IP packets of applications from outside a CGN
device to pass through and be "port forwarded" to the correct user
located behind the CGN device.
The Port Control Protocol (PCP) [RFC6887], provides a mechanism to
create a mapping from an external IP address and port to an internal
IP address and port on a CGN device just to achieve the "port
forwarding" purpose. PCP is a server-client protocol capable of
creating or deleting a mapping along with a rich set of features on a
CGN device in dynamic fashion. In some deployments, all users need
is a few (typically just one) pre-configured port mappings for
applications at home, such as a web cam; the lifetime of such a port
mapping remains valid throughout the duration of the customer's
Internet service connection time. In such an environment, it is
possible to statically configure a port mapping on the RADIUS server
for a user and let the RADIUS protocol propagate the information to
the associated CGN device.
Note that this document targets deployments where a AAA server is
responsible for instructing NAT mappings for a given subscriber and
does not make any assumption about the host's capabilities with
regards to port forwarding control. This deployment is complementary
to PCP given that PCP targets a different deployment model where an
application (on the host) controls its mappings in an upstream CPE,
CGN, firewall, etc.
Figure 18 illustrates how the RADIUS protocol is used to configure a
forwarding
port forwarding mapping on a NAT44 device.
Host CGN/NAS AAA
| BNG Server
| | |
|----Service Request------>| |
| | |
| |---------Access-Request------->|
| | |
| |<--------Access-Accept---------|
| | (IP-Port-Forwarding-Map) |
|<---Service Granted ------| |
| (other parameters) | |
| | |
| (Create a port mapping |
| for the user, and |
| associate it with the |
| internal IP address |
| and external IP address) |
| | |
| | |
| |------Accounting-Request------>|
| | (IP-Port-Forwarding-Map) |
Figure 18: RADIUS Message Flow for Configuring
a Forwarding Port Forwarding Mapping
A port forwarding mapping that is created on a CGN device using the
RADIUS extension as described above may also be changed using a
RADIUS CoA message [RFC5176] that carries the same RADIUS
association. The CoA message may be sent from the RADIUS server
directly to the NAS, and once the RADIUS CoA ACK message is accepted
and sent back, the new port forwarding mapping then replaces the
previous one.
Figure 19 illustrates how the RADIUS protocol is used to change an
existing port mapping from (a:X) to (a:Y), where "a" is an internal
port, and "X" and "Y" are external ports, respectively, for a
specific user with a specific IP address
Host CGN/NAS AAA
| BNG Server
| | |
| Internal IP Address |
| Port Map (a:X) |
| | |
| |<---------CoA Request----------|
| | (IP-Port-Forwarding-Map) |
| | |
| Internal IP Address |
| Port Map (a:Y) |
| | |
| |---------CoA Response--------->|
| | (IP-Port-Forwarding-Map) |
Figure 19: RADIUS Message Flow for Changing
a User's Forwarding Port Forwarding Mapping
4.1.4. An Example
An Internet Service Provider (ISP) assigns TCP/UDP 500 ports for the
user Joe. This number is the limit that can be used for TCP/UDP ports
on a CGN device for Joe and it is configured on a RADIUS server.
Also, Joe asks for a pre-defined port forwarding mapping on the CGN
device for his web cam applications (external port 5000 maps to
internal port 1234).
When Joe successfully connects to the Internet service, the RADIUS
server conveys the TCP/UDP port limit (500) and the forwarding port forwarding
mapping (external port 5000 to internal port 1234) to the CGN device
using the IP-Port-Limit-Info Attribute and IP-Port-Forwarding-Map
Attribute, respectively, carried by an Access-Accept message to the
BNG where NAS and CGN are co-located.
Upon receiving the first outbound IP packet sent from Joe's laptop,
the CGN device decides to allocate a small port pool that contains 40
consecutive ports, from 3500 to 3540, inclusively, and also assigns a
shared IPv4 address 192.0.2.15 for Joe. The CGN device also randomly
selects one port from the allocated range (say, 3519) and uses that
port to replace the original source port in outbound IP packets.
For accounting purposes, the CGN device passes this port range
(3500-3540) and the shared IPv4 address 192.0.2.15 together to the
RADIUS server using IP-Port-Range Attribute carried by an Accounting-
Request message.
When Joe works on more applications with more outbound IP mappings
and the port pool (3500-3540) is close to exhaust, the CGN device
allocates a second port pool (8500-8800) in a similar fashion and
also passes the new port range (8500-8800) and IPv4 address
192.0.2.15 together to the RADIUS server using IP-Port-Range
Attribute carried by an Accounting-Request message. Note when the
CGN allocates more ports, it needs to assure that the total number of
ports allocated for Joe is within the limit.
Joe decides to upgrade his service agreement with more TCP/UDP ports
allowed (up to 1000 ports). The ISP updates the information in Joe's
profile on the RADIUS server, which then sends a CoA-Request message
that carries the IP-Port-Limit-Info Attribute with 1000 ports to the
CGN device; the CGN device in turn sends back a CoA-ACK message.
With that, Joe enjoys more available TCP/UDP ports for his
applications.
When Joe is not using his service, most of the IP mappings are closed
with their associated TCP/UDP ports released on the CGN device, which
then sends the relevant information back to the RADIUS server using
the IP-Port-Range Attribute carried by the Accounting-Request
message.
Throughout Joe's connection with his ISP, applications can
communicate with his web cam at home from the external realm, thus
directly traversing the pre-configured mapping on the CGN device.
When Joe disconnects from his Internet service, the CGN device will
deallocate all TCP/UDP ports as well as the port forwarding mapping
and send the relevant information to the RADIUS server.
4.2. Report Assigned Port Set for a Visiting UE
Figure 20 illustrates an example of the flow exchange that occurs
when the visiting User Equipment (UE) connects to a CPE offering WLAN
service.
For identification purposes (see [RFC6967]), once the CPE assigns a
port set, it issues a RADIUS message to report the assigned port set.
UE CPE CGN AAA
| BNG Server
| | |
| | |
|----Service Request------>| |
| | |
| |-----Access-Request -------->|
| | |
| |<----Access-Accept-----------|
|<---Service Granted ------| |
| (other parameters) | |
... | ... ...
|<---IP@----| | |
| | | |
| (CPE assigns a TCP/UDP port |
| range for this visiting UE) |
| | |
| |--Accounting-Request-...------------------->|
| | (IP-Port-Range |
| | for allocation) |
... | ... ...
| | | |
| | | |
| (CPE withdraws a TCP/UDP port |
| range for a visiting UE) |
| | |
| |--Accounting-Request-...------------------->|
| | (IP-Port-Range |
| | for deallocation) |
| | |
Figure 20: RADIUS Message Flow for Reporting CPE
Allocation/Deallocation of a Port Set to a Visiting UE
5. Table of Attributes
This document proposes three new RADIUS attributes, and their formats
are as follows:
o IP-Port-Limit-Info: 241.5
o IP-Port-Range: 241.6
o IP-Port-Forwarding-Map: 241.7
The following table provides a guide as to what type of RADIUS
packets may contain these attributes and in what quantity.
Request Accept Reject Challenge Acct. # Attribute
Request
0+ 0+ 0 0 0+ 241.5 IP-Port-Limit-Info
0 0 0 0 0+ 241.6 IP-Port-Range
0+ 0+ 0 0 0+ 241.7 IP-Port-Forwarding-Map
The following table defines the meaning of the above table entries.
0 This attribute MUST NOT be present in packet.
0+ Zero or more instances of this attribute MAY be present in packet.
6. Security Considerations
This document does not introduce any security issue other than the
ones already identified in RADIUS documents [RFC2865] and [RFC5176]
for CoA messages. Known RADIUS vulnerabilities apply to this
specification. For example, if RADIUS packets are sent in the clear,
an attacker in the communication path between the RADIUS client and
server may glean information that it will use to prevent a legitimate
user from accessing the service by appropriately setting the maximum
number of IP ports conveyed in an IP-Port-Limit-Info Attribute;
exhaust the port quota of a user by installing many mapping entries
(IP-Port-Forwarding-Map Attribute); prevent incoming traffic from
being delivered to its legitimate destination by manipulating the
mapping entries installed by means of an IP-Port-Forwarding-Map
Attribute; discover the IP address and port range that are assigned
to a given user and reported in an IP-Port-Range Attribute; and so
on. The root cause of these attack vectors is the communication
between the RADIUS client and server.
The IP-Port-Local-Id TLV includes an identifier of which the type and
length is deployment and implementation dependent. This identifier
might carry privacy-sensitive information. It is therefore
RECOMMENDED to utilize identifiers that do not have such privacy
concerns.
If there is any error in a Radius RADIUS Accounting-Request packet sent from
a RADIUS client to the server, the RADIUS server MUST NOT send a
response to the client (refer to [RFC2866]). Examples of the errors
include the erroneous port range in the IP-Port-Range Attribute,
inconsistent port mapping in the IP-Port-Forwarding-Map Attribute,
etc.
This document targets deployments where a trusted relationship is in
place between the RADIUS client and server with communication
optionally secured by IPsec or Transport Layer Security (TLS)
[RFC6614].
7. IANA Considerations
Per this document, IANA has made new code point assignments for both
IPFIX Information Elements and RADIUS attributes as explained in the
following subsections.
7.1. New IPFIX Information Elements
The following IPFIX Information Element has been registered (refer to
Section 3.2.2):
o sourceTransportPortsLimit:
* Name: sourceTransportPortsLimit
* Element ID: 458
* Description: This Information Element (IE) contains the maximum
number of IP source transport ports that can be used by an end
user when sending IP packets; each user is associated with one
or more (source) IPv4 or IPv6 addresses. This IE Information
Element is particularly useful in address-sharing deployments
that adhere to REQ-4 of [RFC6888]. Limiting the number of
ports assigned to each user ensures fairness among users and
mitigates the denial-of-service attack that a user could launch
against other users through the address-sharing device in order
to grab more ports.
* Data type: unsigned16
* Data type semantics: totalCounter
* Data type unit: ports
* Data value range: from 1 to 65535
7.2. New RADIUS Attributes
The Attribute Types defined in this document have been registered by
IANA from the RADIUS namespace as described in the "IANA
Considerations" section of [RFC3575], in accordance with BCP 26
[RFC5226]. For RADIUS packets, attributes, and registries created by
this document, IANA has placed them at
<http://www.iana.org/assignments/radius-types>.
In particular, this document defines three new RADIUS attributes, as
follows, from the Short Extended Space of [RFC6929]:
Type Description Data Type Reference
---- ----------- --------- ---------
241.5 IP-Port-Limit-Info tlv Section 3.1.1
241.6 IP-Port-Range tlv Section 3.1.2
241.7 IP-Port-Forwarding-Map tlv Section 3.1.3
7.3. New RADIUS TLVs
IANA has created a new registry called "RADIUS IP Port Configuration
and Reporting TLVs". All TLVs in this registry have one or more
parent RADIUS attributes in nesting (refer to [RFC6929]). This
registry contains the following TLVs:
Value Description Data Type Reference
----- ----------- --------- ---------
0 Reserved
1 IP-Port-Type integer Section 3.2.1
2 IP-Port-Limit integer Section 3.2.2
3 IP-Port-Ext-IPv4-Addr ipv4addr Section 3.2.3
4 IP-Port-Int-IPv4-Addr ipv4addr Section 3.2.4
5 IP-Port-Int-IPv6-Addr ipv4addr Section 3.2.5
6 IP-Port-Int-Port integer Section 3.2.6
7 IP-Port-Ext-Port integer Section 3.2.7
8 IP-Port-Alloc integer Section 3.2.8
9 IP-Port-Range-Start integer Section 3.2.9
10 IP-Port-Range-End integer Section 3.2.10
11 IP-Port-Local-Id string Section 3.2.11
12-255 Unassigned
The registration procedure for this registry is Standards Action as
defined in [RFC5226].
8. References
8.1. Normative References
[IPFIX] IANA, "IP Flow Information Export (IPFIX) Entities",
<http://www.iana.org/assignments/ipfix/>.
[ProtocolNumbers]
IANA, "Protocol Numbers",
<http://www.iana.org/assignments/protocol-numbers/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, DOI 10.17487/RFC2865, June 2000,
<http://www.rfc-editor.org/info/rfc2865>.
[RFC3575] Aboba, B., "IANA Considerations for RADIUS (Remote
Authentication Dial In User Service)", RFC 3575,
DOI 10.17487/RFC3575, July 2003,
<http://www.rfc-editor.org/info/rfc3575>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6929] DeKok, A. and A. Lior, "Remote Authentication Dial In User
Service (RADIUS) Protocol Extensions", RFC 6929,
DOI 10.17487/RFC6929, April 2013,
<http://www.rfc-editor.org/info/rfc6929>.
[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
for IP Flow Information Export (IPFIX)", RFC 7012,
DOI 10.17487/RFC7012, September 2013,
<http://www.rfc-editor.org/info/rfc7012>.
[RFC8044] DeKok, A., "Data Types in RADIUS", RFC 8044,
DOI 10.17487/RFC8044, January 2017,
<http://www.rfc-editor.org/info/rfc8044>.
8.2. Informative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<http://www.rfc-editor.org/info/rfc1918>.
[RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866,
DOI 10.17487/RFC2866, June 2000,
<http://www.rfc-editor.org/info/rfc2866>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<http://www.rfc-editor.org/info/rfc3022>.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340,
DOI 10.17487/RFC4340, March 2006,
<http://www.rfc-editor.org/info/rfc4340>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<http://www.rfc-editor.org/info/rfc4960>.
[RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Aboba, "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", RFC 5176,
DOI 10.17487/RFC5176, January 2008,
<http://www.rfc-editor.org/info/rfc5176>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <http://www.rfc-editor.org/info/rfc6146>.
[RFC6158] DeKok, A., Ed. and G. Weber, "RADIUS Design Guidelines",
BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011,
<http://www.rfc-editor.org/info/rfc6158>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
P. Roberts, "Issues with IP Address Sharing", RFC 6269,
DOI 10.17487/RFC6269, June 2011,
<http://www.rfc-editor.org/info/rfc6269>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<http://www.rfc-editor.org/info/rfc6333>.
[RFC6598] Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address
Space", BCP 153, RFC 6598, DOI 10.17487/RFC6598, April
2012, <http://www.rfc-editor.org/info/rfc6598>.
[RFC6614] Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
"Transport Layer Security (TLS) Encryption for RADIUS",
RFC 6614, DOI 10.17487/RFC6614, May 2012,
<http://www.rfc-editor.org/info/rfc6614>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<http://www.rfc-editor.org/info/rfc6887>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <http://www.rfc-editor.org/info/rfc6888>.
[RFC6967] Boucadair, M., Touch, J., Levis, P., and R. Penno,
"Analysis of Potential Solutions for Revealing a Host
Identifier (HOST_ID) in Shared Address Deployments",
RFC 6967, DOI 10.17487/RFC6967, June 2013,
<http://www.rfc-editor.org/info/rfc6967>.
[RFC7785] Vinapamula, S. and M. Boucadair, "Recommendations for
Prefix Binding in the Context of Softwire Dual-Stack
Lite", RFC 7785, DOI 10.17487/RFC7785, February 2016,
<http://www.rfc-editor.org/info/rfc7785>.
[TR-146] Broadband Forum, "TR-146: Subscriber Sessions", Broadband
Forum Technical Report 146, Issue 1, May 2013,
<http://www.broadband-forum.org/technical/download/
TR-146.pdf>.
[WIFI-SERVICES]
Gundavelli, S., Grayson, M., Seite, P., and Y. Lee,
"Service Provider Wi-Fi Services Over Residential
Architectures", Work in Progress, draft-gundavelli-v6ops-
community-wifi-svcs-06, April 2013.
Acknowledgments
Many thanks to Dan Wing, Roberta Maglione, Daniel Derksen, David
Thaler, Alan DeKok, Lionel Morand, and Peter Deacon for their useful
comments and suggestions.
Special thanks to Lionel Morand for the Shepherd review and to
Kathleen Moriarty for the AD review.
Thanks to Carl Wallace, Tim Chown, and Ben Campbell for the detailed
review.
Authors' Addresses
Dean Cheng
Huawei
2330 Central Expressway
Santa Clara, California 95050
United States of America
Email: dean.cheng@huawei.com
Jouni Korhonen
Broadcom Corporation
3151 Zanker Road
San Jose 95134
United States of America
Email: jouni.nospam@gmail.com
Mohamed Boucadair
Orange
Rennes
France
Email: mohamed.boucadair@orange.com
Senthil Sivakumar
Cisco Systems
7100-8 Kit Creek Road
Research Triangle Park, North Carolina
United States of America
Email: ssenthil@cisco.com