bind/doc/misc/migration

Copyright (C) 2000, 2001  Internet Software Consortium.
See COPYRIGHT in the source root or http://isc.org/copyright.html for terms.

                   BIND 8 to BIND 9 Migration Notes

BIND 9 is designed to be mostly upwards compatible with BIND 8, but
there is still a number of caveats you should be aware of when
upgrading an existing BIND 8 installation to use BIND 9.


1. Configuration File Compatibility

1.1. Unimplemented Options and Changed Defaults

BIND 9.1 supports most, but not all of the named.conf options of BIND 8.
For a complete list of implemented options, see doc/misc/options.

If your named.conf file uses an unimplemented option, named will log a
warning message.  A message is also logged about each option whose
default has changed unless the option is set explicitly in named.conf.

The default of the "transfer-format" option has changed from
"one-answer" to "many-answers".  If you have slave servers that do not
understand the many-answers zone transfer format (e.g., BIND 4.9.5 or
older) you need to explicitly specify "transfer-format one-answer;" in
either the options block or a server statement.

1.2. Handling of Configuration File Errors

In BIND 9, named refuses to start if it detects an error in
named.conf.  Earlier versions would start despite errors, causing the
server to run with a partial configuration.  Errors detected during
subsequent reloads do not cause the server to exit.

Errors in master files never cause the server to exit.

1.3. Logging

The set of logging categories in BIND 9 is different from that
in BIND 8.  If you have customized your logging on a per-category
basis, you need to modify your logging statement to use the
new categories.

Another difference is that the "logging" statement only takes effect
after the entire named.conf file has been read.  This means that when
the server starts up, any messages about errors in the configuration
file are always logged to the default destination (syslog) when the
server first starts up, regardless of the contents of the "logging"
statement.  In BIND 8, the new logging configuration took effect
immediately after the "logging" statement was read.

1.4. Notify messages and Refesh queries

The source address and port for these is now controlled by
"notify-source" and "transfer-source", respectively, rather that
query-source as in BIND 8.

1.5. Multiple Classes.

Multiple classes have to be put into explicit views for each class.

2. Zone File Compatibility

2.1. Strict RFC1035 Interpretation of TTLs in Zone Files

BIND 8 allowed you to omit all TTLs from a zone file, and used the
value of the SOA MINTTL field as a default for missing TTL values.

BIND 9 enforces strict compliance with the RFC1035 and RFC2308 TTL
rules.  The default TTL is the value specified with the $TTL
directive, or the previous explicit TTL if there is no $TTL directive.
If there is no $TTL directive and the first RR in the file does not
have an explicit TTL field, the error message "no TTL specified" is
logged and loading the zone file fails.

To avoid problems, use a $TTL directive in each zone file.

2.2. Periods in SOA Serial Numbers Deprecated

Some versions of BIND allow SOA serial numbers with an embedded
period, like "3.002", and convert them into integers in a rather
unintuitive way.  This feature is not supported by BIND 9; serial
numbers must be integers.

2.3. Handling of Unbalanced Quotes

TXT records with unbalanced quotes, like 'host TXT "foo', were not
treated as errors in some versions of BIND.  If your zone files
contain such records, you will get potentially confusing error
messages like "unexpected end of file" because BIND 9 will interpret
everything up to the next quote character as a literal string.

2.4. Handling of Line Breaks

Some versions of BIND accept RRs containing line breaks that are not
properly quoted with parentheses, like the following SOA:

	@	IN SOA	ns.example. hostmaster.example.
			( 1 3600 1800 1814400 3600 )

This is not legal master file syntax and will be treated as an error
by BIND 9.  The fix is to move the opening parenthesis to the first
line.

2.5. Unimplemented BIND 8 Extensions

$GENERATE: The "$$" construct for getting a literal $ into a domain
name is deprecated.  Use \$ instead.

3. Interoperability Impact of New Protocol Features

3.1. EDNS0

BIND 9 uses EDNS0 (RFC2671) to advertise its receive buffer size.  It
also sets an EDNS flag bit in queries to indicate that it wishes to
receive DNSSEC responses; this flag bit usage is not yet standardized,
but we hope it will be.

Most older servers that do not support EDNS0, including prior versions
of BIND, will send a FORMERR or NOTIMP response to these queries.
When this happens, BIND 9 will automatically retry the query without
EDNS0.

Unfortunately, there exists at least one non-BIND name server
implementation that silently ignores these queries instead of sending
an error response.  Resolving names in zones where all or most
authoritative servers use this server will be very slow or fail
completely.  We have contacted the manufacturer of the name server in
case, and they are working on a solution.

3.2. Zone transfers

Outgoing zone transfers now use the "many-answers" format by default.
This format is not understood by certain old versions of BIND 4.  
You can work around this problem using the option "transfer-format
one-answer;", but since these old versions all have known security
problems, the correct fix is to upgrade the slave servers.

Some BIND 9 users have reported interoperability problems with zone
transfers to Microsoft DNS servers that were solved by specifying
"transfer-format one-answer;", but we are still lacking detailed
information about this issue.


4. Unrestricted Character Set

BIND 9 does not restrict the character set of domain names - it is
fully 8-bit clean in accordance with RFC2181 section 11.

It is strongly recommended that hostnames published in the DNS follow
the RFC952 rules, but BIND 9 will not enforce this restriction.

Historically, some applications have suffered from security flaws
where data originating from the network, such as names returned by
gethostbyaddr(), are used with insufficient checking and may cause a
breach of security when containing unexpected characters; see
<http://www.cert.org/advisories/CA-96.04.corrupt_info_from_servers.html>
for details.  Some earlier versions of BIND attempt to protect these
flawed applications from attack by discarding data containing
characters deemed inappropriate in host names or mail addresses, under
the control of the "check-names" option in named.conf and/or "options
no-check-names" in resolv.conf.  BIND 9 provides no such protection;
if applications with these flaws are still being used, they should
be upgraded.


5. Server Administration Tools

The "ndc" program has been replaced by "rndc", which is capable of
remote operation.  Unlike ndc, rndc requires a configuration file; 
see the man pages in bin/rndc/rndc.1 and bin/rndc/rndc.conf.5 for
details.  Some of the ndc commands are still unimplemented in rndc.


6. No Information Leakage between Zones

BIND 9 stores the authoritative data for each zone in a separate data
structure, as recommended in RFC1035 and as required by DNSSEC and
IXFR.  When a BIND 9 server is authoritative for both a child zone and
its parent, it will have two distinct sets of NS records at the
delegation point: the authoritative NS records at the child's apex,
and a set of glue NS records in the parent.

BIND 8 was unable to properly distinguish between these two sets of NS
records and would "leak" the child's NS records into the parent,
effectively causing the parent zone to be silently modified: responses
and zone transfers from the parent contained the child's NS records
rather than the glue configured into the parent (if any).  In the case
of children of type "stub", this behavior was documented as a feature,
allowing the glue NS records to be omitted from the parent
configuration.

Sites that were relying on this BIND 8 behavior need to add any
omitted glue NS records, and any necessary glue A records, to the
parent zone.

Although stub zones can no longer be used as a mechanism for injecting
NS records into their parent zones, they are still useful as a way of
directing queries for a given domain to a particular set of name
servers.


$Id: migration,v 1.29 2001/04/25 17:35:10 gson Exp $