draft-ietf-dhc-fqdn-opt-01.txt   draft-ietf-dhc-fqdn-opt-02.txt 
Network Working Group Yakov Rekhter, Cisco Systems Network Working Group Yakov Rekhter, cisco Systems
INTERNET DRAFT Ralph Droms, Bucknell University INTERNET DRAFT Ralph Droms, Bucknell University
Obsoletes: draft-ietf-dhc-fqdn-opt-00.txt April 1996 Obsoletes: draft-ietf-dhc-fqdn-opt-01.txt March 1997
Expires October 1996 Expires September 1997
An option for FQDNs in DHCP options An option for FQDNs in DHCP options
<draft-ietf-dhc-fqdn-opt-01.txt> <draft-ietf-dhc-fqdn-opt-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
skipping to change at page 1, line 43 skipping to change at page 1, line 43
rather than Fully Qualified Domain Names (FQDN). Use of IP addresses rather than Fully Qualified Domain Names (FQDN). Use of IP addresses
constrains the DHCP client to use the addresses that were in use at constrains the DHCP client to use the addresses that were in use at
the time the client received its configuration information; these the time the client received its configuration information; these
addresses may change over time, (e.g., a server may be assigned a new addresses may change over time, (e.g., a server may be assigned a new
IP address), so that the IP addresses used by the client may become IP address), so that the IP addresses used by the client may become
invalid. invalid.
An alternative to passing IP addresses is to pass FQDNs instead of An alternative to passing IP addresses is to pass FQDNs instead of
(numeric) IP addresses. Doing this allows to defer binding between a (numeric) IP addresses. Doing this allows to defer binding between a
particular network entity (e.g., a server) and its IP address until particular network entity (e.g., a server) and its IP address until
run time. As stated in [Carpenter:95], "Deferring the binding avoids run time. As stated in [Carpenter:96], "Deferring the binding avoids
the risk of changed mapping between IP addresses and specific network the risk of changed mapping between IP addresses and specific network
entities (due to changing addressing information). Moreover, entities (due to changing addressing information). Moreover,
reliance on FQDNs (rather than IP addresses) also localizes to the reliance on FQDNs (rather than IP addresses) also localizes to the
DNS the changes needed to deal with changing addressing information DNS the changes needed to deal with changing addressing information
due to renumbering." due to renumbering."
DRAFT An option for FQDNs in DHCP options April 1996 DRAFT An option for FQDNs in DHCP options March 1997
This document defines a new DHCP option that allows the use of FQDNs This document defines a new DHCP option that allows the use of FQDNs
instead of IP addresses in DHCP options. instead of IP addresses in DHCP options.
Definitions 1. FQDN Option
The following defines the format of the FQDN option. The FQDN option allows the use of FQDNs rather than IP addresses in
DHCP options. The FQDN option contains other DHCP options, which
then carry FQDNs rather than IP addresses as data.
The code for the FQDN option is 89. The Len field gives the total
length of all of the DHCP options contained in the FQDN option. The
Code, Len, Subcode and Sublen are all one octet long. The FQDN field
is variable length.
For each subcode carried in the FQDN option, the IP address in the
option represented by the subcode is replaced by a FQDN.
The Sublen field shall be set to the length (in octets) of the FQDN
carried in the option. The FQDN field carries the FQDN itself.
+----------+----------+ +----------+----------+
| Code | Length | | Code | Len |
+----------+----------+---------+-----------+-------------------- +----------+----------+---------+-----------+--------------------
|Subcode |Sublength | FQDN | Subcode | Sublen | FQDN
+----------+----------+---------+-----------+-------------------- +----------+----------+---------+-----------+--------------------
.................. ..................
+----------+----------+---------+-----------+-------------------- +----------+----------+---------+-----------+--------------------
|Subcode |Sublength | FQDN | Subcode | Sublen | FQDN
+----------+----------+---------+-----------+-------------------- +----------+----------+---------+-----------+--------------------
The option consists of a Code and Length fields followed by a 1.1 DHCP options containing a list of parameters
variable number of <subcode, sublength, FQDN> triples.
The code, length, subcode, and sublength fields are all one octet
long. The FQDN field is of variable length.
The code value for this option is TBD.
The length field specifies the total length (in octets) of all the
triples carried in the option.
For each subcode carried in the FQDN option, the IP address in the More that one triple with a given subcode may appear within a single
option represented by the subcode is replace by a FQDN. FQDN option. The FQDNs contained in triples with the same subcode
should be treated as a list of parameters for the DHCP option
represented by the subcode.
The sublength field shall be set to the length (in octets) of the Because FQDNs are variable length, lists of FQDNs cannot be encoded
FQDN carried in the option. The FQDN field carries the FQDN itself. in DHCP options within the FQDN option. DHCP Options that can carry
a list of IP addresses should be coded as multiple subcodes in the
FQDN option, to differentiate among the variable-length FQDNs.
More that one triple with a given subcode may appear within a single DRAFT An option for FQDNs in DHCP options March 1997
FQDN option. Options that can carry a list of IP addresses should be
coded as multiple subcodes in the FQDN option, to differentiate among
the variable-length FQDNs.
This option only allows the use of FQDNs for options that have been This option only allows the use of FQDNs for options that have been
elsewhere defined to carry IP addresses. elsewhere defined to carry IP addresses.
DRAFT An option for FQDNs in DHCP options April 1996 1.2 Example
Example
The following illustrates how the FQDN option could be used to carry The following illustrates how the FQDN option could be used to carry
FQDNs for 2 LPR Servers with FQDNs lpr1.xxx.org and lpr2.yy.org, and FQDNs for 2 LPR Servers with FQDNs lpr1.xxx.org and lpr2.yy.org, and
one Network Information Server with FQDN nis.zzzz.org. one Network Information Server with FQDN nis.zzzz.org.
+---+---+ +---+---+
|xx |41 | |xx |41 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|41 |12 | n | i | s | . | z | z | z | z | . | o | r | g | |41 |12 | n | i | s | . | z | z | z | z | . | o | r | g |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 9 |12 | l | p | r | 1 | . | x | x | x | . | o | r | g | | 9 |12 | l | p | r | 1 | . | x | x | x | . | o | r | g |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 9 |11 | l | p | r | 2 | . | y | y | . | o | r | g | | 9 |11 | l | p | r | 2 | . | y | y | . | o | r | g |
+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+
Security Considerations 2. Security Considerations
Security issues are not discussed in this document. Security issues are not discussed in this document.
References 3. References
[Carpenter:95] Carpenter, B., Rekhter, Y., "Renumbering considered [Carpenter:96] Carpenter, B., Rekhter, Y., "Renumbering needs work",
unavoidable", Internet Draft RFC1900, February 1996.
[DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541, [DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541,
October 1993 October 1993.
Acknowledgements 4. Acknowledgments
To be supplied. The authors gratefully acknowledge the input and review of the
Dynamic Host Configuration working group. They also thank cisco
Systems and Bucknell University for their support in the development
of this document.
DRAFT An option for FQDNs in DHCP options April 1996 DRAFT An option for FQDNs in DHCP options March 1997
Author Information 5. Author Information
Yakov Rekhter Yakov Rekhter
cisco Systems, Inc. cisco Systems, Inc.
170 Tasman Dr. 170 Tasman Dr.
San Jose, CA 95134 San Jose, CA 95134
Phone: (914) 528-0090 Phone: (914) 528-0090
email: yakov@cisco.com email: yakov@cisco.com
Ralph Droms Ralph Droms
Computer Science Department Computer Science Department
 End of changes. 

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