draft-ietf-dhc-relay-id-suboption-05.txt   draft-ietf-dhc-relay-id-suboption-06.txt 
DHC M. Stapp DHC M. Stapp
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: June 19, 2009 December 16, 2008 Intended status: Standards Track December 18, 2008
Expires: June 21, 2009
The DHCPv4 Relay Agent Identifier Suboption The DHCPv4 Relay Agent Identifier Suboption
draft-ietf-dhc-relay-id-suboption-05.txt draft-ietf-dhc-relay-id-suboption-06.txt
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Abstract Abstract
This memo defines a new Relay Agent Identifier suboption for the This memo defines a new Relay Agent Identifier suboption for the
Dynamic Host Configuration Protocol's (DHCP) Relay Agent Information Dynamic Host Configuration Protocol's (DHCP) Relay Agent Information
option. The suboption carries a value that uniquely identifies the option. The suboption carries a value that uniquely identifies the
relay agent device. The value may be administratively-configured or relay agent device. The value may be administratively-configured or
may be generated by the relay agent. The suboption allows a DHCP may be generated by the relay agent. The suboption allows a DHCP
relay agent to include the identifier in the DHCP messages it sends. relay agent to include the identifier in the DHCP messages it sends.
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Example Use-Cases . . . . . . . . . . . . . . . . . . . . . . . 3 3. Example Use-Cases . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Industrial Ethernet . . . . . . . . . . . . . . . . . . . . 3 3.1. Industrial Ethernet . . . . . . . . . . . . . . . . . . . . 3
3.2. Bulk Leasequery . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Bulk Leasequery . . . . . . . . . . . . . . . . . . . . . . 4
4. Suboption Format . . . . . . . . . . . . . . . . . . . . . . . 4 4. Suboption Format . . . . . . . . . . . . . . . . . . . . . . . 4
5. Relay Identifier Types . . . . . . . . . . . . . . . . . . . . 5 5. Relay Identifier Types . . . . . . . . . . . . . . . . . . . . 5
6. Generating a Relay Identifier . . . . . . . . . . . . . . . . . 5 6. Generating a Relay Identifier . . . . . . . . . . . . . . . . . 5
7. Identifier Stability . . . . . . . . . . . . . . . . . . . . . 5 7. Identifier Stability . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
1. Introduction 1. Introduction
The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131] The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131]
provides IP addresses and configuration information for IPv4 clients. provides IP addresses and configuration information for IPv4 clients.
It includes a relay agent capability, in which network elements It includes a relay agent capability, in which network elements
receive broadcast messages from clients and forward them to DHCP receive broadcast messages from clients and forward them to DHCP
servers as unicast messages. In many network environments, relay servers as unicast messages. In many network environments, relay
agents add information to the DHCP messages before forwarding them, agents add information to the DHCP messages before forwarding them,
using the Relay Agent Information option [RFC3046]. Servers that using the Relay Agent Information option [RFC3046]. Servers that
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supply information that a DHCP server could use as a client supply information that a DHCP server could use as a client
identifier. A straightforward way to form identifier information is identifier. A straightforward way to form identifier information is
to combine something that is unique within the scope of the network to combine something that is unique within the scope of the network
element, such as a port/slot value, with something that uniquely element, such as a port/slot value, with something that uniquely
identifies that network element, such as a Relay Agent Identifier. identifies that network element, such as a Relay Agent Identifier.
3.2. Bulk Leasequery 3.2. Bulk Leasequery
There has been quite a bit of recent interest in extending the DHCP There has been quite a bit of recent interest in extending the DHCP
Leasequery protocol [RFC4388] to accommodate some additional Leasequery protocol [RFC4388] to accommodate some additional
situations. There are two recent drafts ([draft-kinnear] and situations. There is a recent draft ([draft-kinnear]) proposing a
[draft-dtv]) proposing a variety of enhancements to the existing variety of enhancements to the existing Leasequery protocol. The
Leasequery protocol. [draft-dtv] describes a use-case where a relay draft describes a use-case where a relay agent queries DHCP servers
agent queries DHCP servers using the Relay Identifier to retrieve all using the Relay Identifier to retrieve all the leases allocated
the leases allocated through the relay device. through the relay device.
4. Suboption Format 4. Suboption Format
Format of the Relay Agent Identifier suboption: Format of the Relay Agent Identifier suboption:
0 1 2 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 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_RELAY_ID| length | type | | |SUBOPT_RELAY_ID| length | type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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field contains an ASCII string. field contains an ASCII string.
6. Generating a Relay Identifier 6. Generating a Relay Identifier
As described in Section 1, in some situations it may be useful for As described in Section 1, in some situations it may be useful for
network devices to generate identifiers themselves. Relay agents who network devices to generate identifiers themselves. Relay agents who
send the Relay Agent Identifier suboption using identifiers that are send the Relay Agent Identifier suboption using identifiers that are
not administratively-configured MUST be generated following the not administratively-configured MUST be generated following the
procedures in the DUID section of [RFC3315]. Relay agents who use procedures in the DUID section of [RFC3315]. Relay agents who use
generated identifiers SHOULD make the generated value visible to generated identifiers SHOULD make the generated value visible to
their administrators via their user-interface, through a log entry, their administrators via their user interface, through a log entry,
or through some other mechanism. or through some other mechanism.
7. Identifier Stability 7. Identifier Stability
If the relay identifier is to be meaningful it has to be stable. A If the relay identifier is to be meaningful it has to be stable. A
relay agent SHOULD use a single identifier type and value relay agent SHOULD use a single identifier type and value
consistently. The identifier used by a relay device SHOULD be consistently. The identifier used by a relay device SHOULD be
committed to stable storage, unless the relay device can regenerate committed to stable storage, unless the relay device can regenerate
the value upon reboot. the value upon reboot.
Implementors should note that the identifier needs to be present in Implementors should note that the identifier needs to be present in
all DHCP message types where its value is being used by the DHCP all DHCP message types where its value is being used by the DHCP
server. The relay agent may not be able to add the Relay Agent server. The relay agent may not be able to add the Relay Agent
Information option to all messages - such as RENEW messages sent as Information option to all messages - such as RENEW messages sent as
IP unicasts. In some deployments that might mean that the server has IP unicasts. In some deployments that might mean that the server has
to be willing to continue to associate the relay-identifier it has to be willing to continue to associate the relay identifier it has
last seen with a lease that is being RENEWed. Other deployments may last seen with a lease that is being RENEWed. Other deployments may
prefer to use the Server Identifier Override suboption [RFC5107] to prefer to use the Server Identifier Override suboption [RFC5107] to
permit the relay device to insert the Information option into all permit the relay device to insert the Information option into all
relayed messages. relayed messages.
Handling situations where a relay agent device is replaced is another
aspect of "stability". One of the use-cases for the relay identifier
is to permit a server to associate clients' lease bindings with the
relay device connected to the clients. If the relay device is
replaced, because it has failed or been upgraded, it may be desirable
for the new device to continue to provide the same relay identifier
as the old device. Implementors should be aware of this possibility,
and consider making it possible for administrators to configure the
identifier.
8. Security Considerations 8. Security Considerations
Security issues with the Relay Agent Information option and its use Security issues with the Relay Agent Information option and its use
by servers in address assignment are discussed in [RFC3046] and by servers in address assignment are discussed in [RFC3046] and
[RFC4030]. Relay agents who send the Relay Agent Identifier [RFC4030]. Relay agents who send the Relay Agent Identifier
suboption SHOULD use the Relay Agent Authentication suboption suboption SHOULD use the Relay Agent Authentication suboption
[RFC4030] to provide integrity protection. [RFC4030] to provide integrity protection.
9. IANA Considerations 9. IANA Considerations
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[RFC5107] Johnson, R., Kumarasamy, J., Kinnear, K., and M. Stapp, [RFC5107] Johnson, R., Kumarasamy, J., Kinnear, K., and M. Stapp,
"DHCP Server Identifier Override Suboption", RFC 5107, "DHCP Server Identifier Override Suboption", RFC 5107,
February 2008. February 2008.
[draft-kinnear] [draft-kinnear]
Kinnear, K., Volz, B., Russell, N., and M. Stapp, "Bulk Kinnear, K., Volz, B., Russell, N., and M. Stapp, "Bulk
DHCPv4 Lease Query DHCPv4 Lease Query
(draft-kinnear-dhc-dhcpv4-bulk-leasequery-*)", July 2008. (draft-kinnear-dhc-dhcpv4-bulk-leasequery-*)", July 2008.
[draft-dtv]
Rao, D., Joshi, B., and P. Kurapati, "DHCPv4 bulk lease
query (draft-dtv-dhc-dhcpv4-bulk-leasequery-*)",
July 2008.
Author's Address Author's Address
Mark Stapp Mark Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave. 1414 Massachusetts Ave.
Boxborough, MA 01719 Boxborough, MA 01719
USA USA
Phone: +1 978 936 0000 Phone: +1 978 936 0000
Email: mjs@cisco.com Email: mjs@cisco.com
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