Submitted to DHC Working Group Peter De Schrijver INTERNET DRAFT Yves T'Joens
<draft-ietf-dhc-pv4-reconfigure-02.txt><draft-ietf-dhc-pv4-reconfigure-03.txt> Christian Hublet Alcatel November 2000April 2001 Expires June,September, 2001 DHCP reconfigure extension Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months. Internet-Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet- Drafts as reference material or to cite them other than as a ``working draft'' or ``work in progress.'' The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txthttp://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directorieson ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au(Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this memo is unlimited. Abstract This draft defines extensions to DHCP [DHCP] to allow dynamic reconfiguration of a single host triggered by the DHCP server (eg. a new IP address). This is achieved by introducing a unicast DHCP FORCERENEW message which forces the client to the RENEW state. The behaviour for hosts using the DHCP INFORM message to obtain configuration information is also described. 1. Introduction The procedures as described within this draft allow the dynamic reconfiguration of individual hosts. 1.1 Conventions 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]. 2. DHCP force renew This section describes the DHCP force renew extension. 2.1 Terminology DHCP client : host to be reconfigured using DHCP. DHCP server : server which configured the DHCP client. 2.2 Force renew procedures The DHCP server sends a force renew message to the client. The client will change its state to the RENEW state. The client will then try to renew its lease according to normal DHCP procedures. If the server wants to assign a new IP address to the client, it will reply to the DHCP 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. If the force renew message is lost, the DHCP server will not receive a DHCP REQUEST from the client and it should retransmit the DHCP FORCERENEW message using an exponential backoff algorithm. Depending on the bandwidth of the network between server and client, the server should choose a delay. This delay grows exponentially as retransmissions fail. The amount of retransmissions should be limited. It can be that a client has obtained a network address through some other means (e.g., manual configuration) and has used a DHCPINFORM request to obtain other local configuration parameters. Such clients should respond to the receipt of DHCP FORCERENEW message with a new DHCP INFORM request so as to obtain a potential new set of local configuration parameters. 2.3 Rationale This approach has a number of advantages. It does not require new 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 driven by the server, which can be used to optimize network usage or DHCP server load. 3. Extended DHCP state diagram +--------+ +------+ | Init / | +-->+ Init +<---------------+-------------------+ | Reboot | | +--+---+ | | +---+----+ DHCPNAK/ -/Send DHCPDISCOVER | | | Restart | (broadcast) | | | | v v-------------+ | | -/Send DHCPREQUEST| +----+------+ DHCPOFFER/DHCPDECLINE | | (broadcast)| | Selecting |----------+ | | v | +----+------+ | | +---+----+ | DHCPOFFER/DHCPREQUEST | | | Reboot +---------+ (broadcast) | | +---+----+ v | | | +----+-------+ DHCPNAK /halt network | + Requesting | | lease expired DHCPACK/ +----+-------+ | | Record lease | | | set timers DHCPACK/Record lease | | | v Set T1 & T2 | | | +--+----+DHCPFORCE +---+---+ +----+---+ +----------------->+ Bound +---------->+ Renew +--------->+ Rebind | +--+-+--+T1 expires +-+-+---+T2 expires+----+---+ ^ /DHCPREQUEST | | /broadcast | DHCPACK to leasing | | DHCPREQUEST | | server | | | +----------------------------------------+ 4. Message layout Field DHCPFORCERENEW ----- --------------- 'op' BOOTREPLY 'htype' (From "Assigned Numbers" RFC) '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 The new value for DHCP option 53 (DHCP message type) to indicate a DHCPFORCERENEW message is TBD. 6. Security Considerations As in some network environments DHCPFORCERENEW can be used to snoop and spoof traffic, the DHCPFORCERENEW message MUST be authenticated using the procedures as described in [DHCP-AUTH]. 7. References [DHCP] R.Droms, "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [DHCP-AUTH] R. Droms et al., "Authentication for DHCP Messages", draft-ietf-dhc-authentication-14, July 2000, Work in progress.RFCxxxx, yyyy 2001. [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8. Acknowledgements The authors would like to thank David Allen, Nortel, for the contribution to these procedures. 9. Contacts Peter De Schrijver Alcatel Network Strategy Group Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 8569 E-mail : email@example.com Yves T'joens Alcatel Network Strategy Group Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 7890 E-mail : firstname.lastname@example.org Christian Hublet Alcatel Carrier Internetworking Division De Villermontstraat 28, 2550 Kontich, Belgium Phone : +32 3 450 3322 E-mail : Christian.Hublet@alcatel.be 8. 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