Mobile IP Working Group Jayshree Bharatia Internet Draft Kuntal Chowdhury Category: Standards Track Nortel Networks Expires on September 2002 March 2002 Mobile IPv4 Extension: Using DNS Servers Assigned by Home Agent 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 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 Abstract This draft provides an extension to Mobile IPv4 protocol where the Mobile Node (MN) obtains an information regarding DNS Servers from a home agent. This is achieved by defining a new extension of a Registration Reply message. 1 Introduction Currently, There is no explicit mechanism defined in [RFC3320] for assigning primary and secondary DNS servers in the IP network. In any case, the MN has to obtain information of the DNS Servers. This information can be passed to the MN by the IP network or it can be obtained by some other means like the use of DHCP etc. This draft basically considers a scenario where Mobile Node obtains DNS addresses from the IP network. In this proposal, both primary and secondary DNS servers are assigned by the Home Agent (HA) and their information is passed to the MN after successful Mobile IPv4 Registration procedure. This proposed solution is more generic and does not rely on the use of any specific link layer. Note that the scope of this document is to emphasize on the mechanism by which the information regarding DNS server addresses are relayed to MN. It does Bharatia,Chowdhury Expires September 2002 1 not include discussion of how DNS server addresses are obtained by the HA. Note that this draft does not preclude supporting this extension in the foreign network. If reverse tunneling is not supported and the HA does not return the DNS server address extensions in the Registration Reply message, then the FA may append DNS sever address extensions to the Registration Reply message before relaying the Registration Reply to the MN. But there might be some security issues involved with this option. 1.1 Glossary of Terms FA Foreign Agent HA Home Agent MN Mobile Node DNS Domain Name Server 2 Conventions used in this document 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. 3 Detailed Description of the Proposed Solution This draft provides a mechanism to convey DNS addresses from the HA to the MN. This information is passed to the MN during successful Mobile IP Registration procedure. The message flow of the solution is shown in figure 1. Upon successful Mobile IP Registration, the HA appends IP addresses of DNS servers in the Registration Reply message with new Mobile IP extension (defined in section 4). The MN receives this extension and sets the corresponding fields in the DNS lookup accordingly. MN FA HA -- -- -- 1. <----Agent Advertisement------ 2. -----Registration Request----> 3. ----Registration Request------------- 4. <---Registration Response------------ (w/ Extension for DNS) 5. <--Registration Response------ (w/ Extension for DNS) Figure 1-Exchanges of DNS Servers Information Figure 1 shows message exchanges between different Mobile IP entities. In this figure, steps 1-3 are normal message exchanges for Mobile IP support. Bharatia,Chowdhury Expires September 2002 2 Step 4: The HA appends Mobile IPv4 extension (discussed in section 4) for primary and secondary DNS servers. Step 5: The FA forwards the Registration Reply message to the MN. When MN receives this new Mobile IP extension, it sets the DNS lookup accordingly. 4 DNS Extension The Mobile IP extension for primary and secondary DNS servers shall have the following format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | DNS-Address_primary | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DNS-Address_primary (cont) | DNS-Address_secondary | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DNS-Address_secondary (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type DNS-IPV4-EXT-TYPE=TBD. This extension value will be assigned by IANA from the numbering space defined for Mobile IP Registration Reply extensions in [RFC3220] Length 10 DNS-Address_primary The DNS-Address_primary (4 octets) is the address of primary DNS server to be used by the MN. DNS-Address_secondary The DNS-Address_secondary (4 octets) is the address of secondary DNS server to be used by the MN. 5 IANA Considerations This draft defines a new Mobile IPv4 extension of type DNS-IPV4-EXT- TYPE as defined in section 4 of this document. The value will be defined by IANA from the numbering space defined for the Registration Reply in [RFC3220]. 6 Security Considerations There are no additional security aspects imposed by this document in addition to the one defined in [RFC3320]. 7 References [RFC3320] "IP Mobility Support for IPv4", RFC3320 8 Acknowledgments Authors like to thank Pete Wenzel, Tom Hussey and Glenn Morrow for their valuable input to this work 9 Author's Address Bharatia,Chowdhury Expires September 2002 3 Jayshree Bharatia Nortel Networks 2221, Lakeside Blvd, Richardson, TX-75082 Phone : 972-684-5767 jayshree@nortelnetworks.com Kuntal Chowdhury Nortel Networks 2221, Lakeside Blvd, Richardson, TX-75082 Phone : 972-685-7788 chowdury@nortelnetworks.com Bharatia,Chowdhury Expires September 2002 4