draft-ietf-dnsext-dnsproxy-04.txt   draft-ietf-dnsext-dnsproxy-05.txt 
DNSEXT R. Bellis DNSEXT R. Bellis
Internet-Draft Nominet UK Internet-Draft Nominet UK
Intended status: BCP April 15, 2009 Intended status: BCP April 23, 2009
Expires: October 17, 2009 Expires: October 25, 2009
DNS Proxy Implementation Guidelines DNS Proxy Implementation Guidelines
draft-ietf-dnsext-dnsproxy-04 draft-ietf-dnsext-dnsproxy-05
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 17, 2009. This Internet-Draft will expire on October 25, 2009.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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Support for UDP packet sizes exceeding the WAN MTU depends on the Support for UDP packet sizes exceeding the WAN MTU depends on the
gateway's algorithm for handling fragmented IP packets. Several gateway's algorithm for handling fragmented IP packets. Several
methods are possible: methods are possible:
1. fragments are dropped 1. fragments are dropped
2. fragments are forwarded individually as they're received 2. fragments are forwarded individually as they're received
3. complete packets are reassembled on the gateway, and then re- 3. complete packets are reassembled on the gateway, and then re-
fragmented (if necessary) as they're forwarded to the client fragmented (if necessary) as they're forwarded to the client
Method 1 above will cause compatibility problems with EDNS0 unless Method 1 above will cause compatibility problems with EDNS0 unless
the DNS client is configured to advertise an EDNS0 buffer size the DNS client is configured to advertise an EDNS0 buffer size
limited to 28 octets less than the MTU. Note that RFC 2671 does limited to the WAN MTU less the size of the IP header. Note that RFC
recommend that the path MTU should be taken into account when using 2671 does recommend that the path MTU should be taken into account
EDNS0. when using EDNS0.
Also, whilst the EDNS0 specification allows for a buffer size of up Also, whilst the EDNS0 specification allows for a buffer size of up
to 65535 octets, most common DNS server implementations do not to 65535 octets, most common DNS server implementations do not
support a buffer size above 4096 octets. support a buffer size above 4096 octets.
Therefore (irrespective of which of the methods above is in use) Therefore (irrespective of which of the methods above is in use)
proxies SHOULD be capable of forwarding UDP packets up to a payload proxies SHOULD be capable of forwarding UDP packets up to a payload
size of at least 4096 octets. size of at least 4096 octets.
NB: in theory IP fragmentation may also occur if the LAN MTU is NB: in theory IP fragmentation may also occur if the LAN MTU is
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instead of dropping the packet completely. instead of dropping the packet completely.
7. IANA Considerations 7. IANA Considerations
This document requests no IANA actions. This document requests no IANA actions.
8. Change Log 8. Change Log
NB: to be removed by the RFC Editor before publication. NB: to be removed by the RFC Editor before publication.
draft-ietf-dnsproxy-05
Removed specific reference to 28 byte IP headers (from Mark
Andrews)
draft-ietf-dnsproxy-04 - post WGLC draft-ietf-dnsproxy-04 - post WGLC
Introduction expanded Introduction expanded
Section 5.2 - changed SHOULD to MUST Section 5.2 - changed SHOULD to MUST
Section 4.5 - changed SHOULD to MUST (Alex Bligh) Section 4.5 - changed SHOULD to MUST (Alex Bligh)
Editorial nits (from Andrew Sullivan, Alfred Hones) Editorial nits (from Andrew Sullivan, Alfred Hones)
Clarificaton on end-user vs device administrator (Alan Barrett, Clarificaton on end-user vs device administrator (Alan Barrett,
Paul Selkirk) Paul Selkirk)
draft-ietf-dnsproxy-03 draft-ietf-dnsproxy-03
Editorial nits and mention of LAN MTU (from Alex Bligh) Editorial nits and mention of LAN MTU (from Alex Bligh)
 End of changes. 5 change blocks. 
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