draft-ietf-dhc-pv4-reconfigure-03.txt   draft-ietf-dhc-pv4-reconfigure-04.txt 
Submitted to DHC Working Group Peter De Schrijver Submitted to DHC Working Group Peter De Schrijver
INTERNET DRAFT Yves T'Joens INTERNET DRAFT Yves T'Joens
<draft-ietf-dhc-pv4-reconfigure-03.txt> Christian Hublet <draft-ietf-dhc-pv4-reconfigure-04.txt> Christian Hublet
Alcatel Alcatel
April 2001 April 2001
Expires September, 2001 Expires September, 2001
DHCP reconfigure extension DHCP reconfigure extension
Status of this memo Status of this memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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Abstract Abstract
This draft defines extensions to DHCP [DHCP] to allow dynamic This draft defines extensions to DHCP [DHCP] to allow dynamic
reconfiguration of a single host triggered by the DHCP server (eg. a reconfiguration of a single host triggered by the DHCP server (eg. a
new IP address). This is achieved by introducing a unicast DHCP new IP address). This is achieved by introducing a unicast FORCERENEW
FORCERENEW message which forces the client to the RENEW state. The message which forces the client to the RENEW state. The behaviour for
behaviour for hosts using the DHCP INFORM message to obtain hosts using the DHCP INFORM message to obtain configuration
configuration information is also described. information is also described.
1. Introduction 1. Introduction
The procedures as described within this draft allow the dynamic The procedures as described within this draft allow the dynamic
reconfiguration of individual hosts. reconfiguration of individual hosts.
1.1 Conventions 1.1 Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. DHCP force renew 2. DHCP force renew
This section describes the DHCP force renew extension. This section describes the FORCERENEW message extension.
2.1 Terminology 2.1 Terminology
DHCP client : host to be reconfigured using DHCP. DHCP client : host to be reconfigured using DHCP.
DHCP server : server which configured the DHCP client. DHCP server : server which configured the DHCP client.
2.2 Force renew procedures 2.2 Force renew procedures
The DHCP server sends a force renew message to the client. The client The DHCP server sends a unicast FORCERENEW message to the client.
will change its state to the RENEW state. The client will then try to Upon receipt of the unicast FORCERENEW message, the client will
renew its lease according to normal DHCP procedures. If the server change its state to the RENEW state, and will then try to renew its
wants to assign a new IP address to the client, it will reply to the lease according to normal DHCP procedures. If the server wants to
DHCP REQUEST with a DHCP NAK. The client will then go back to the assign a new IP address to the client, it will reply to the DHCP
init state and broadcast a DHCP DISCOVER message. The server can now REQUEST with a DHCP NAK. The client will then go back to the init
state and broadcast a DHCP DISCOVER message. The server can now
assign a new IP address to the client by replying with a DHCP OFFER. assign a new IP address to the client by replying with a DHCP OFFER.
If the force renew message is lost, the DHCP server will not receive If the FORCERENEW message is lost, the DHCP server will not receive a
a DHCP REQUEST from the client and it should retransmit the DHCP DHCP REQUEST from the client and it should retransmit the FORCERENEW
FORCERENEW message using an exponential backoff algorithm. Depending message using an exponential backoff algorithm. Depending on the
on the bandwidth of the network between server and client, the server bandwidth of the network between server and client, the server should
should choose a delay. This delay grows exponentially as choose a delay. This delay grows exponentially as retransmissions
retransmissions fail. The amount of retransmissions should be fail. The amount of retransmissions should be limited.
limited.
The procedures described above assume the server to send a unicast
FORCERENEW message to the client. Receipt of a multicast FORCERENEW
message by the client should be silently discarded.
It can be that a client has obtained a network address through some It can be that a client has obtained a network address through some
other means (e.g., manual configuration) and has used a DHCPINFORM other means (e.g., manual configuration) and has used a DHCPINFORM
request to obtain other local configuration parameters. Such clients request to obtain other local configuration parameters. Such clients
should respond to the receipt of DHCP FORCERENEW message with a new should respond to the receipt of a unicast FORCERENEW message with a
DHCP INFORM request so as to obtain a potential new set of local new DHCP INFORM request so as to obtain a potential new set of local
configuration parameters. configuration parameters.
2.3 Rationale 2.3 Rationale
This approach has a number of advantages. It does not require new This approach has a number of advantages. It does not require new
states to be added to the DHCP client implementation. This minimizes states to be added to the DHCP client implementation. This minimizes
the amount of code to be changed. It also allows lease RENEWAL to be the amount of code to be changed. It also allows lease RENEWAL to be
driven by the server, which can be used to optimize network usage or driven by the server, which can be used to optimize network usage or
DHCP server load. DHCP server load.
skipping to change at page 3, line 35 skipping to change at page 3, line 38
| +--+----+DHCPFORCE +---+---+ +----+---+ | +--+----+DHCPFORCE +---+---+ +----+---+
+----------------->+ Bound +---------->+ Renew +--------->+ Rebind | +----------------->+ Bound +---------->+ Renew +--------->+ Rebind |
+--+-+--+T1 expires +-+-+---+T2 expires+----+---+ +--+-+--+T1 expires +-+-+---+T2 expires+----+---+
^ /DHCPREQUEST | | /broadcast | ^ /DHCPREQUEST | | /broadcast |
DHCPACK to leasing | | DHCPREQUEST | DHCPACK to leasing | | DHCPREQUEST |
| server | | | | server | | |
+----------------------------------------+ +----------------------------------------+
4. Message layout 4. Message layout
Field DHCPFORCERENEW The FORCERENEW message makes use of the normal DHCP message layout
----- --------------- with the introduction of a new DHCP message type. DHCP option 53
'op' BOOTREPLY (DHCP message type) is extended with a new value : DHCPFORCERENEW
'htype' (From "Assigned Numbers" RFC) (TBD)
'hlen' (Hardware address length in octets)
'hops' 0
'xid' selected by server
'secs' 0
'ciaddr' 0
'yiaddr' 0
'siaddr' 0
'flags' 0
'giaddr' 0
'chaddr' client's hardware address
'sname' 0
'file' 0
'options' options
DHCP option 53 (DHCP message type) is extended with a new value :
DHCPFORCERENEW (TBD)
5. IANA Considerations 5. IANA Considerations
The new value for DHCP option 53 (DHCP message type) to indicate a The new value for DHCP option 53 (DHCP message type) to indicate a
DHCPFORCERENEW message is TBD. DHCPFORCERENEW message is TBD.
6. Security Considerations 6. Security Considerations
As in some network environments DHCPFORCERENEW can be used to snoop As in some network environments FORCERENEW can be used to snoop and
and spoof traffic, the DHCPFORCERENEW message MUST be authenticated spoof traffic, the FORCERENEW message MUST be authenticated using the
using the procedures as described in [DHCP-AUTH]. procedures as described in [DHCP-AUTH]. FORCERENEW messages failing
the authentication should be silently discarded by the client.
7. References 7. References
[DHCP] R.Droms, "Dynamic Host Configuration Protocol", RFC 2131, [DHCP] R.Droms, "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[DHCP-AUTH] R. Droms et al., "Authentication for DHCP Messages", [DHCP-AUTH] R. Droms et al., "Authentication for DHCP Messages",
RFCxxxx, yyyy 2001. RFCxxxx, yyyy 2001.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
8. Acknowledgements 8. Acknowledgements
The authors would like to thank David Allen, Nortel, for the The authors would like to thank David Allan, Nortel, for the
contribution to these procedures. constructive comments to these procedures.
9. Contacts 9. Contacts
Peter De Schrijver Peter De Schrijver
Alcatel Network Strategy Group Alcatel Network Strategy Group
Francis Wellesplein 1, 2018 Antwerp, Belgium Francis Wellesplein 1, 2018 Antwerp, Belgium
Phone : +32 3 240 8569 Phone : +32 3 240 8569
E-mail : peter.de_schrijver@alcatel.be E-mail : peter.de_schrijver@alcatel.be
Yves T'joens Yves T'joens
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