| Rfc | 7839 |
|---|
| Title | Access-Network-Identifier Option in DHCP |
|---|
| Author | S. Bhandari, S.
Gundavelli, M. Grayson, B. Volz, J. Korhonen |
|---|
| Date | June 2016 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Internet Engineering Task Force (IETF) S. Bhandari
Request for Comments: 7839 S. Gundavelli
Category: Standards Track M. Grayson
ISSN: 2070-1721 B. Volz
Cisco Systems
J. Korhonen
Broadcom Limited
June 2016
Access-Network-Identifier Option in DHCP
Abstract
This document specifies the format and mechanism that is to be used
for encoding Access-Network Identifiers in DHCPv4 and DHCPv6 messages
by defining new Access-Network-Identifier options and sub-options.
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/rfc7839.
Copyright Notice
Copyright (c) 2016 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.
1. Introduction
Access-network identification of a network device has a range of
applications. For example, the Local Mobility Anchor (LMA) in a
Proxy Mobile IPv6 (PMIPv6) domain is able to provide service
treatment for the mobile node's traffic based on the access network
to which the mobile node is attached.
This document specifies the Dynamic Host Configuration Protocol for
IPv4 (DHCPv4) [RFC2131] and the Dynamic Host Configuration Protocol
for IPv6 (DHCPv6) [RFC3315] options for access-network identification
that is added by the relay agent in the DHCPv4 or DHCPv6 messages
sent towards the server. The scope of applicability for this option
is between a DHCP relay agent and a mobile access gateway where the
same operator typically operates both these functions
A DHCP relay agent that is aware of the access network and access
operator adds this information in the DHCP messages. This
information can be used to provide differentiated services and
policing of traffic based on the access network to which a client is
attached. Examples of how this information can be used in mobile
networks can be found in [RFC6757].
2. Motivation
PMIPv6 [RFC5213] can be used for supporting network-based mobility
management in various types of network deployments. The network
architectures, such as service provider Wi-Fi access aggregation or
WLAN integrated mobile packet core, are examples where PMIPv6 is a
component of the overall architecture. Some of these architectures
require the ability of the LMA [RFC5213] to provide differentiated
services and policing of traffic to the mobile nodes based on the
access network to which they are attached. Policy systems in
mobility architectures, such as Policy and Charging Control (PCC)
[TS23203] and Access Network Discovery and Selection Function (ANDSF)
[TS23402] in the 3GPP system, allow configuration of policy rules
with conditions based on the access-network information. For
example, the service treatment for the mobile node's traffic may be
different when they are attached to an access network owned by the
home operator than when owned by a roaming partner. In the case of
access networks based on IEEE 802.11, the service treatment can also
be different based on the configured Service Set Identifiers (SSIDs).
Other examples of services include the operator's ability to apply
tariff based on the location.
The PMIPv6 extension as specified in [RFC6757] defines PMIPv6 options
to carry Access-Network Identifiers in PMIPv6 signaling from the
Mobile Access Gateway (MAG) to the LMA. The MAG can learn this
information from the DHCP options as inserted by the DHCP relay agent
in the access network. If the MAG relays the DHCP messages to the
LMA as specified in [RFC5844], this information can be inserted by
the MAG towards the LMA in the forwarded DHCP messages.
Figure 1 illustrates an example of PMIPv6 deployment. In this
example, the access network is based on IEEE 802.11 technology, the
DHCP relay agent function is located on the Access Point (AP), and
the DHCP server function is located on the MAG. The MAG delivers the
information elements related to the access network to the LMA over
PMIPv6 signaling messages. The MAG obtains these information
elements from the DHCP relay agent as per this specification. The
information elements related to the access network include the SSID
of the used IEEE 802.11 network, the geo-location of the access
network to which the mobile node is attached, and the identity of the
operator running the IEEE 802.11 access-network infrastructure.
SSID: IETF-1
Operator-Identifier: provider1.example
+--+
|AP|-----------. {Access-Specific Policies)
+--+ | (DHCP Server) _-----_ |
(DHCP Relay) +-----+ _( )_ +-----+
| MAG |-=========( PMIPv6 )======-| LMA |-
+-----+ (_ Tunnel_) +-----+
+--+ | '-----'
|AP|-----------'
+--+
(DHCP Relay)
SSID: IETF-2
Operator-Identifier: provider2.example
Access Networks Attached to MAG
3. Terminology
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].
All the DHCP-related terms used in this document are to be
interpreted as defined in DHCPv4 [RFC2131] and DHCPv6 [RFC3315]
specifications. "DHCP message" refers to both DHCPv4 and DHCPv6
messages throughout this document.
All the mobility-related terms used in this document are to be
interpreted as defined in the PMIPv6 specifications [RFC5213] and
[RFC5844]. Additionally, this document uses the following
abbreviations:
Service Set Identifier (SSID)
The Service Set Identifier (SSID) identifies the name of the IEEE
802.11 network. The SSID differentiates from one network to the
other.
Operator-Identifier
The Operator-Identifier is the Structure of Management Information
(SMI) Network Management Private Enterprise Code of the IANA-
maintained "Private Enterprise Numbers" registry [SMI]. It
identifies the operator running the access network where the
client is attached.
4. DHCPv4 Access-Network-Identifier Option
The Access-Network Identifier (ANI) carries information related to
the identity of the access network to which the client is attached.
This information includes access-technology type, network identifier,
and access network operator identifiers.
Relay agents that include ANI information include one or more sub-
options (see Section 4.1) in the Relay Agent Information option
[RFC3046].
4.1. DHCPv4 Access-Network-Identifier Sub-options
The Access-Network-Identifier information will be defined in multiple
sub-options allocated from the "DHCP Relay Agent Sub-Option Codes"
registry.
ANI Sub-options: The ANI sub-options consist of a sequence of Sub-
Option Code, Length, and Value tuples for each sub-option, encoded in
the following manner:
Subopt Len Sub-option Data
+------+------+------+------+------+------+--...-+------+
| code | N | s1 | s2 | s3 | s4 | | sN |
+------+------+------+------+------+------+--...-+------+
Subopt code
The 1-octet code for the sub-options defined in the following
sections.
Len
An unsigned 8-bit integer giving the length of the Sub-option Data
field in this sub-option in octets.
Sub-option Data (s1 to sN)
The data area for the sub-option.
The initial assignment of the DHCP Access-Network-Identifier sub-
options is as follows:
+=================+=======================================+
| SUB-OPTION CODE | SUB-OPTION DESCRIPTION |
+=================+=======================================+
| 13 | Access-Technology-Type Sub-option |
+=========================================================+
| 14 | Access-Network-Name Sub-option |
+=========================================================+
| 15 | Access-Point-Name Sub-option |
+=========================================================+
| 16 | Access-Point-BSSID Sub-option |
+=========================================================+
| 17 | Operator-Identifier Sub-option |
+=========================================================+
| 18 | Operator-Realm Sub-option |
+=========================================================+
4.2. DHCPv4 Access-Technology-Type Sub-option
This sub-option is used for exchanging the type of the access
technology of the network to which the client is attached. Its
format is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | Reserved | ATT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
13
Length
2
Reserved
An 8-bit field that is unused for now. The value MUST be
initialized to 0 by the sender and MUST be ignored by the
receiver.
Access-Technology-Type (ATT)
An 8-bit field that specifies the access technology through which
the client is connected to the access link from the IANA name
space "Access Technology Type Option type values" registry defined
in [RFC5213].
4.3. DHCPv4 Network-Identifier Sub-options
These sub-options are used for carrying the name of the access
network (e.g., an SSID in the case of an IEEE 802.11 access network
or a Public Land-based Mobile Network (PLMN) Identifier [TS23003] in
the case of a 3GPP access network) and the Access-Point Name to which
the client is attached. The format of these sub-options is defined
in the following sections. The Network-Identifier sub-options are
only for the currently known access-technology types.
4.3.1. DHCPv4 Network-Name Sub-option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. .
. Network-Name (e.g., SSID or PLMNID) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
14
Length
The length of the Network-Name field.
Network-Name
The name of the access network to which the mobile node is
attached. The encoding MUST be UTF-8 as described in [RFC3629].
The type of the Network-Name is dependent on the access technology
to which the mobile node is attached. For networks based on IEEE
802.11, the Network-Name will be the SSID of the network. For
3GPP access-based networks, it is the PLMN Identifier of the
access network, and for 3GPP2 access, the Network-Name is the ANI
[ANI].
When encoding the PLMN Identifier, both the Mobile Network Code
(MNC) [TS23003] and Mobile Country Code (MCC) [TS23003] MUST be
three digits. If the MNC in use only has two digits, then it MUST
be preceded with a '0'.
4.3.2. DHCPv4 Access-Point-Name Sub-option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. .
. Access-Point-Name .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
15
Length
The length of the Access-Point-Name field.
Access-Point-Name
The name of the access point (physical device name) to which the
mobile node is attached. This is the identifier that uniquely
identifies the access point. While the Network-Name (e.g., SSID)
identifies the operator's access network, the Access-Point-Name
identifies a specific network device in the network to which the
mobile node is attached. In some deployments, the Access-Point-
Name can be set to the string representation of the Media Access
Control (MAC) address of the device as specified in [RFC6991] (see
mac-address typedef) or some unique identifier that can be used by
the policy systems in the operator network to unambiguously
identify the device. The encoding MUST be UTF-8 as described in
[RFC3629].
4.3.3. DHCPv4 Access-Point-BSSID Sub-option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Access-Point-BSSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
16
Length
6
Access-Point-BSSID
The 48-bit Basic SSSID (BSSID) of the access point to which the
mobile node is attached.
4.4. DHCPv4 Operator-Identifier Sub-options
The Operator-Identifier sub-options can be used for carrying the
Operator-Identifiers of the access network to which the client is
attached. The format of these sub-options is defined below.
4.4.1. DHCPv4 Operator-Identifier Sub-option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Operator-Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
17
Length
4
Operator-Identifier
The Operator-Identifier is a variable-length Private Enterprise
Number (PEN) [SMI] encoded in a network byte order. Please refer
to Section 3.1.3 of [RFC6757] for additional details.
4.4.2. DHCPv4 Operator-Realm Sub-option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt Code | Length | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. .
. Operator-Realm .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Subopt Code
18
Length
The length of the Operator-Realm field.
Operator-Realm
Realm of the operator (e.g., EXAMPLE.COM). Please refer to
Section 3.1.3 of [RFC6757] for additional details.
5. DHCPv6 Access-Network-Identifier Options
The Access-Network-Identifier options defined here may be added by
the DHCPv6 relay agent in Relay-forward messages.
+=================+=======================================+
| OPTION CODE | OPTION DESCRIPTION |
+=================+=======================================+
| 105 | OPTION_ANI_ATT |
+=========================================================+
| 106 | OPTION_ANI_NETWORK_NAME |
+=========================================================+
| 107 | OPTION_ANI_AP_NAME |
+=========================================================+
| 108 | OPTION_ANI_AP_BSSID |
+=========================================================+
| 109 | OPTION_ANI_OPERATOR_ID |
+=========================================================+
| 110 | OPTION_ANI_OPERATOR_REALM |
+=========================================================+
5.1. DHCPv6 Access-Technology-Type Option
This option is used for exchanging the type of access technology the
client uses to attach to the network. Its format is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_ATT | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | ATT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_ATT (105)
Option-Len
2
Reserved
An 8-bit field that is unused for now. The value MUST be
initialized to 0 by the sender and MUST be ignored by the
receiver.
Access-Technology-Type (ATT):
The contents of this field are the same as the ATT field described
in Section 4.2.
5.2. DHCPv6 Network-Identifier Options
These options can be used for carrying the name of the access network
(e.g., an SSID in the case of an IEEE 802.11 access network or a PLMN
Identifier [TS23003] in the case of a 3GPP access network) and an
Access-Point Name to which the client is attached. The format of
these options is defined below.
5.2.1. DHCPv6 Network-Name Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_NETWORK_NAME | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Network-Name (e.g., SSID or PLMNID) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_NETWORK_NAME (106)
Option-Len
The length of the Network-Name field.
Network-Name
The contents of this field are the same as the Network-Name field
described in Section 4.3.1.
5.2.2. DHCPv6 Access-Point-Name Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_AP_NAME | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Access-Point-Name .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_AP_NAME (107)
Option-Len
The length of the Access-Point-Name field.
Access-Point-Name
The contents of this field are the same as the Access-Point-Name
field described in Section 4.3.2.
5.2.3. DHCPv6 Access-Point-BSSID Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_AP_BSSID | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Access-Point-BSSID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_AP_BSSID (108)
Option-Len
6
Access-Point-BSSID
The contents of this field are the same as the Access-Point-BSSID
field described in Section 4.3.3.
5.3. DHCPv6 Operator-Identifier Options
The Operator-Identifier options can be used for carrying the
Operator-Identifier of the access network to which the client is
attached. The format of these options is defined below.
5.3.1. DHCPv6 Operator-Identifier Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_OPERATOR_ID | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Operator-Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_OPERATOR_ID (109)
Option-Len
4
Operator-Identifier
The contents of this field are the same as the DHCPv4 Operator-
Identifier Sub-option field described in Section 4.4.1.
5.3.2. DHCPv6 Operator-Realm Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ANI_OPERATOR_REALM | Option-Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Operator-Realm .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Code
OPTION_ANI_OPERATOR_REALM (110)
Option-Len
The length of the Operator-Realm field.
Operator-Realm
The contents of this field are the same as the Operator-Realm
field described in Section 4.4.2.
6. Relay Agent Behavior
DHCPv4 relay agents MAY include sub-options as defined in Section 4.2
through 4.4 of [RFC3046] in the Relay Agent Information option for
providing information about the access network over which DHCP
messages from the client are received.
The DHCPv4 relay agent MUST include the DHCPv4 Access-Technology-Type
Sub-option (Section 4.2) when including any of these sub-options in
the DHCP message: DHCPv4 Network-Name Sub-option (Section 4.3.1),
DHCPv4 Access-Point-Name Sub-option (Section 4.3.2), and DHCPv4
Access-Point-BSSID Sub-option (Section 4.3.3).
DHCPv6 Relay Agents MAY include options (defined in Section 5) in the
Relay-forward message when forwarding any DHCPv6 message type from
clients to the servers to provide information about the access
network over which DHCPv6 messages from the client are received.
The DHCPv6 relay agent MUST include the DHCPv6 Access-Technology-Type
Option (Section 5.1) when including any of these options in the DHCP
message: DHCPv6 Network-Name Option (Section 5.2.1), DHCPv6 Access-
Point-Name Option (Section 5.2.2), and DHCPv6 Access-Point-BSSID
Option (Section 5.2.3).
7. Server Behavior
The DHCPv4 base specification [RFC2131] requires that the DHCPv4
server ignore the DHCPv4 Access-Network-Identifier Option if it does
not understand the option.
If the DHCPv4 server does not understand the received sub-option
defined in Sections 4.1 through 4.4 of [RFC3046], the DHCPv4 Relay-
Agent-Information Option, it MUST ignore those sub-options only. If
the DHCPv4 server is able to process the DHCPv4 Access-Network-
Identifier sub-options defined in Sections 4.1 through 4.4 of
[RFC3046], the DHCPv4 Relay-Agent-Information Option, it MAY use this
information obtained from the sub-option for address pool selection
or for policy decisions as per its configured policy. This
information obtained from the sub-option SHOULD NOT be stored unless
it is absolutely needed. However, if it is stored, the information
MUST be deleted as quickly as possible to eliminate any possibility
of the information getting exposed to an intruder.
The DHCPv4 server MUST ignore the received DHCPv4 Access-Network-
Identifier Option and process the rest of the message as per the base
DHCPv4 specifications if the received DHCPv4 message does not include
the DHCPv4 Access-Technology-Type Sub-option (Section 4.2) but does
include any one of these other options: DHCPv4 Network Name Sub-
option (Section 4.3.1), DHCPv4 Access-Point-Name Sub-option
(Section 4.3.2), or DHCPv4 Access-Point-BSSID Sub-option
(Section 4.3.3).
DHCPv6 base specification [RFC3315] requires that the DHCPv6 server
ignore the DHCPv6 Access-Network-Identifier Option if it does not
understand the option.
If the DHCPv6 server receives the options defined in Section 5 and is
configured to use the options defined in Section 5, it SHOULD look
for the DHCPv6 Access-Network-Identifier options in the Relay-forward
message of the DHCPv6 relay agent(s) based on its configured policy.
The server MAY use received ANI options for its address pool
selection policy decisions as per its configured policy. This
information obtained from the options SHOULD NOT be stored unless it
is absolutely needed. However, if it is stored, the information MUST
be deleted as quickly as possible to eliminate any possibility of the
information getting exposed to an intruder.
The DHCPv6 server MUST ignore the received DHCPv6 Access-Network-
Identifier Option and process the rest of the message as per the base
DHCPv6 specifications if the received DHCPv6 message does not include
the DHCPv6 Access-Technology-Type Option (Section 5.1) but it does
includes any one of these other options: DHCPv6 Network-Name Option
(Section 5.2.1), DHCPv6 Access-Point-Name Option (Section 5.2.2), or
DHCPv6 Access-Point-BSSID Option (Section 5.2.3).
8. IANA Considerations
IANA has assigned sub-option codes for the following DHCPv4 sub-
options from the "DHCP Relay Agent Sub-Option Codes" registry,
<http://www.iana.org/assignments/bootp-dhcp-parameters>:
+=================+=======================================+
| SUB-OPTION CODE | SUB-OPTION DESCRIPTION |
+=================+=======================================+
| 13 | Access-Technology-Type Sub-option |
+=========================================================+
| 14 | Access-Network-Name Sub-option |
+=========================================================+
| 15 | Access-Point-Name Sub-option |
+=========================================================+
| 16 | Access-Point-BSSID Sub-option |
+=========================================================+
| 17 | Operator-Identifier Sub-option |
+=========================================================+
| 18 | Operator-Realm Sub-option |
+=========================================================+
IANA has assigned option codes for the following DHCPv6 options from
the "Option Codes" registry for DHCPv6,
<http://www.iana.org/assignments/dhcpv6-parameters>, as specified in
[RFC3315]:
+=================+=======================================+
| OPTION CODE | OPTION DESCRIPTION |
+=================+=======================================+
| 105 | OPTION_ANI_ATT |
+=========================================================+
| 106 | OPTION_ANI_NETWORK_NAME |
+=========================================================+
| 107 | OPTION_ANI_AP_NAME |
+=========================================================+
| 108 | OPTION_ANI_AP_BSSID |
+=========================================================+
| 109 | OPTION_ANI_OPERATOR_ID |
+=========================================================+
| 110 | OPTION_ANI_OPERATOR_REALM |
+=========================================================+
9. Security Considerations
Since there is no privacy protection for DHCP messages, an
eavesdropper who can monitor the link between the DHCP server and
relay agent can discover access-network information.
[RFC3118] and [RFC3315] describe many of the threats in using DHCP.
[RFC3118] and [RFC3315] each provide a solution; the Authentication
Option for DHCPv4 and DHCPv6 (respectively). However, neither of
these options are in active use and therefore are not a viable
mitigation option. DHCP itself is inherently insecure and thus link-
layer confidentiality and integrity protection SHOULD be employed to
reduce the risk of disclosure and tampering.
It is possible for a rogue DHCP relay agent to insert or overwrite
with incorrect Access-Network-Identifier options for malicious
purposes. A DHCP client can also pose as a rogue DHCP relay agent by
sending incorrect Access-Network-Identifier options. While the
introduction of fraudulent DHCP relay agent information options can
be prevented by a perimeter defense that blocks these options unless
the DHCP relay agent is trusted, a deeper defense using the
authentication sub-option for the DHCPv4 Relay-Agent-Information
Option [RFC4030] SHOULD be deployed as well. Administrators SHOULD
configure DHCP servers that use this option to communicate with their
relay agents using IPsec, as described in Section 21.1 of [RFC3315].
The information elements that this document is exposing are the
client's access-network information. These pertain to the access
network to which the client is attached, such as Access-Technology
Type (e.g., WLAN, Ethernet, etc.), Access-Point Identity (Name,
BSSID), and Operator-Identifier and Operator-Realm. In deployments
where this information cannot be secured using IPsec [RFC4301] or
other security protocols, administrators SHOULD disable the
capability specified in this document on the DHCP entities.
10. References
10.1. Normative References
[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>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<http://www.rfc-editor.org/info/rfc2131>.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, DOI 10.17487/RFC3046, January 2001,
<http://www.rfc-editor.org/info/rfc3046>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>.
10.2. Informative References
[ANI] "Interoperability Specification (IOS) for High Rate Packet
Data (HRPD) Radio Access Network Interfaces with Session
Control in the Access Network", 3GPP2 A.S0008-C v4.0,
April 2011.
[RFC3118] Droms, R., Ed. and W. Arbaugh, Ed., "Authentication for
DHCP Messages", RFC 3118, DOI 10.17487/RFC3118, June 2001,
<http://www.rfc-editor.org/info/rfc3118>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC4030] Stapp, M. and T. Lemon, "The Authentication Suboption for
the Dynamic Host Configuration Protocol (DHCP) Relay Agent
Option", RFC 4030, DOI 10.17487/RFC4030, March 2005,
<http://www.rfc-editor.org/info/rfc4030>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<http://www.rfc-editor.org/info/rfc5213>.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010,
<http://www.rfc-editor.org/info/rfc5844>.
[RFC6757] Gundavelli, S., Ed., Korhonen, J., Ed., Grayson, M.,
Leung, K., and R. Pazhyannur, "Access Network Identifier
(ANI) Option for Proxy Mobile IPv6", RFC 6757,
DOI 10.17487/RFC6757, October 2012,
<http://www.rfc-editor.org/info/rfc6757>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<http://www.rfc-editor.org/info/rfc6991>.
[SMI] IANA, "PRIVATE ENTERPRISE NUMBERS, SMI Network Management
Private Enterprise Codes", March 2016,
<https://www.iana.org/assignments/enterprise-numbers>.
[TS23003] 3GPP, "Numbering, addressing and identification", 3GPP
TS 23.003 13.4.0, December 2015.
[TS23203] 3GPP, "Policy and charging control architecture", 3GPP
TS 23.203 13.6.0, December 2015.
[TS23402] 3GPP, "Architecture enhancements for non-3GPP accesses",
3GPP TS 23.402 13.4.0, December 2015.
Acknowledgements
The authors would like to thank Kim Kinnear, Ted Lemon, Gaurav
Halwasia, Hidetoshi Yokota, Sheng Jiang, and Francis Dupont for their
valuable input. Also, thank you to Tomek Mrugalski for a thorough
review of the document.
Authors' Addresses
Shwetha Bhandari
Cisco Systems
Cessna Business Park, Sarjapura Marathalli Outer Ring Road
Bangalore, KARNATAKA 560 087
India
Phone: +91 80 4426 0474
Email: shwethab@cisco.com
Sri Gundavelli
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
United States
Email: sgundave@cisco.com
Mark Grayson
Cisco Systems
11 New Square Park
Bedfont Lakes, FELTHAM TW14 8HA
England
Email: mgrayson@cisco.com
Bernie Volz
Cisco Systems
1414 Massachusetts Ave
Boxborough, MA 01719
United States
Email: volz@cisco.com
Jouni Korhonen
Broadcom Limited
3151 Zanker Rd
San Jose, CA 95134
United States
Email: jouni.nospam@gmail.com