--- 1/draft-ietf-dhc-relay-agent-flags-02.txt 2007-05-01 22:12:05.000000000 +0200 +++ 2/draft-ietf-dhc-relay-agent-flags-03.txt 2007-05-01 22:12:05.000000000 +0200 @@ -1,19 +1,19 @@ DHC K. Kinnear Internet-Draft M. Normoyle Intended status: Standards Track M. Stapp -Expires: August 2, 2007 Cisco Systems, Inc. - January 29, 2007 +Expires: October 25, 2007 Cisco Systems, Inc. + April 23, 2007 DHCPv4 Relay Agent Flags Suboption - draft-ietf-dhc-relay-agent-flags-02.txt + draft-ietf-dhc-relay-agent-flags-03.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that @@ -24,21 +24,21 @@ and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on August 2, 2007. + This Internet-Draft will expire on October 25, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This memo defines a new suboption of the DHCP relay agent information option that allows the DHCP relay to specify flags for the forwarded packet. One flag is defined to indicate whether the DHCP relay @@ -47,22 +47,22 @@ based on whether their request was originally broadcast or unicast. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 3 3. The Flags Suboption . . . . . . . . . . . . . . . . . . . . . . 4 4. DHCP Relay Agent Behavior . . . . . . . . . . . . . . . . . . . 4 5. DHCP Server Behavior . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 - 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 + 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 8 1. Introduction Any time a client's DHCP packet is broadcast, a local DHCP relay will process its request and forward it on to the DHCP server. When the @@ -80,21 +80,24 @@ a locally connected network, or a unicast packet from a DHCP Relay Agent which has forwarded on a packet broadcast from a DHCP client connected to a network local to the DHCP Relay Agent. In some situations, DHCP Clients may unicast their DHCPREQUEST/RENEW packets to the DHCP Relay Agent, which will forward the packet on to the DHCP server. In these cases, the DHCP server cannot tell whether the packet was broadcast or unicast by the DHCP client, and so it may be unable to process the DHCP client packets in the manner that it would if it knew whether the original DHCP packet was broadcast or - unicast. + unicast. For example, a server might be willing to NAK a client in + the REBINDING state based on a determination that the client's + address does not match its location in the network, but might not be + willing to do so if the client is in the RENEWING state. The purpose of the suboption described in this document is to allow the DHCP relay to specify flags for the forwarded packet. These flags can be used to describe DHCP client attributes that are useful to the DHCP server, but can only be detected by the local DHCP relay. The DHCP server can use the information provided by the DHCP relay to improve its processing algorithms. One flag is defined to indicate whether the DHCP relay received the packet via a unicast or broadcast packet. This allows the DHCP @@ -133,50 +136,64 @@ U: UNICAST flag unicast = 1 broadcast = 0 MBZ: MUST BE ZERO (reserved for future use) 4. DHCP Relay Agent Behavior - A DHCP relay agent MUST include this suboption in every Relay Agent - Information Option [RFC3046] it adds to a forwarded DHCP request. In - this way, the DHCP server can distinguish a request forwarded from a - DHCP relay agent which does not support the relay-agent-flags - suboption from a request forwarded by a DHCP relay agent which - supports the relay-agent-flags suboption and which received the - request that is being forwarded in a broadcast packet. + A DHCP relay agent that claims to conform to this specification MUST + include this suboption in every Relay Agent Information Option + [RFC3046] it adds to a forwarded DHCP request. In this way, the DHCP + server can distinguish a request forwarded from a DHCP relay agent + that does not support the relay-agent-flags suboption from a request + forwarded by a DHCP relay agent that supports the relay-agent-flags + suboption and which received the request that is being forwarded in a + broadcast packet. To put this another way, A DHCP relay agent which supports the relay- agent-flags suboption MUST always include it in every relay-agent- information-option that it inserts into packets which it forwards on to the DHCP server, whether the packet it is forwarding was received as a broadcast or as a unicast. This is because the DHCP server will be dealing with DHCP relay agents that support the relay-agent-flags suboption as well as DHCP relay agents that do not support the relay- agent-flags suboption. 5. DHCP Server Behavior This option provides additional information to the DHCP server. The DHCP server MAY use this information to make processing decisions regarding the DHCP Client's packet which it is processing. For instance, knowledge of the broadcast or unicast reception of a packet - by a DHCP relay agent is important when making the processing - decisions required to implement Load Balancing [RFC3074]. + by a DHCP relay agent could be used when making the processing + decisions required to implement Load Balancing [RFC3074]. A load- + balancing server may be willing to respond to a REBINDING client, but + the server cannot determine the client's state without this + additional indication. The option length is one octet. If the DHCP server receives a relay- agent-flags suboption that is longer than one octet, it MUST evaluate the first octet. + Note to implementors: In specifying the behavior of new flags bits in + the future, careful attention must be paid to compatibility with + earlier implementations. If additional flags values are defined in + the future, it will not always be possible to distinguish between + messages from relay agents who understand the new value and set its + value to 'zero', and relay agents who are simply setting a series of + unassigned bits to 'zero'. It would be a mistake to specify + significant behavior changes based on 'zero' values of flags + specified in the future. + 6. Security Considerations Message authentication in DHCP for intradomain use where the out-of- band exchange of a shared secret is feasible is defined in [RFC3118]. Potential exposures to attack are discussed in section 7 of the DHCP protocol specification in [RFC2131]. The DHCP Relay Agent option depends on a trusted relationship between the DHCP relay agent and the server, as described in section 5 of [RFC3046]. While the introduction of fraudulent relay-agent options