From a presentation on the new IPv6 support in Sametime 8.0.2.

What IPv6 is about

- IPv4 has been in use ever since the public internet is around
- Addresses in IPv4 consist of 32 bits
- This allows a virtual number of up to 4G different addresses
- There are probably much more computers than addresses
- To accommodate this number, NAT has been used so far
- NAT has its weaknesses (some application protocols need the NAT gateway to parse and re-construct their messages)
- Addresses in IPv6 consist of 128 bits
- This allows a virtual number of up to 256EE (>3e+38) addresses
- In addition to the address size, other features, mainly security related are added in IPv6 as an integral part of the IP layer

Not covered in this article
- Configuring Domino
- Configuring LDAP, DNS and other organizational servers
- Configuring HTTP servers, proxies and reverse proxies
- Configuring operating systems to support IPv6

Main challenges
- Parsing IPv6 colon notation
- IP addresses as message parameters VP (Sametime) protocol
- Hosts with multiple IP addresses
- Resolving a name to a single IP address
- Server config in dual vs. separate stack platforms
- Mux config in dual vs. separate stack platforms

IPv6 colon notation
- Reminder: IPv4 addresses consist of 32 bits, represented by 4 segments of 8 bit decimal numbers, separated by dots, For example: 9.148.202.87
- Addresses consist of 128 bits, represented by 8 segments of 16-bit hexadecimal numbers, separeted by colons, For example, 2001:0:0:0:20c:29ff:fe89:4232
- One sequence of zero segments can be condensed to a double colon, the above address = 2001::20c:29ff:fe89:4232
- IPv4-friendly notation: the last 32 bits of an IPv6 address can be given in IPv4 dotted notation,
For example: the above address = 2001::20c:29ff:254.137.66.50
- IPv4 addresses can be represented in IPv6 notation using the ::ffff:0:0/96 address class, For example: 9.148.202.87 = ::ffff:9.148.202.87
NOTE: These are actual IPv4 addresses, even though they can be represented in IPv6 notation

IP addresses as message parameters
in VP (Sametime) protocol
- Sametime passes IP addresses as parameters in quite a few protocol messages
- A few messages pass the address as its string representation
- In most messages it is passed as a raw 32 bit (4 bytes) value
- NG (new generation) address representation in VP protocol:

type (1 byte) followed by value (number of bytes determined by type).
Types: 0=Invalid (no value), 1=IPv4 (+4 bytes), 2=IPv6 (+16 bytes)

- For the sake of protocol backward compatibility, NG messages were added as new messages rather than modifying the existing ones
- Since old (pre-ST8.0.2) components do not support the new NG messages, IPv6 is only supported when all components (servers, clients, muxes, SAs, GWs, etc.) are ST8.0.2 or above.

Hosts with multiple IP addresses
- Servers identify themselves by IP addresses
- Other servers and standalone muxes identify the servers by their IP addresses
- The traditional way to “guess” the local IP address is to resolve the local hostname to a single address
- Since IPv6 support in the OS usually creates multiple addresses, the difficulties typical to multiple IP addresses are more common when IPv6 is enabled
- Legacy related sametime.ini settings, For example: VPMX_IP, VPS_LOCALHOST
- Recommended sametime.ini setting since ST8.0: UCM_LOCAL_IP
- Use UCM_LOCAL_IP with VPS_HOST
- Correct addresses, same type

Resolving a name to a single IP addresses
- When a name resolves to a single address, it’s easy
- When a name resolves to multiple addresses Sametime code chooses one
- Native (C++) components choose the address with the lowest numeric value, preferring IPv4 addresses
- Java components choose the first address in the list, preferring IPv4 addresses
- To override the default IPv4/6 preference in native components: UCM_RESOLVE_PREFERRED_IP_VER in sametime.ini
- To override the default IPv4/6 preference in Java components: java.net.preferIPv6Addresses in system properties

Server config in dual and separate stack OS
- Since the server is recognized by other servers and muxes by its IP address, it must communicate with them through that address
- The idea of UDN presented in the spec was supposed to change this (servers to be identified by their UDN rather than IP address) but proved too big a change
- In order for a server to accept SA connections in addresses other than its main one (for SAs that don’t care about server ID), the VPS_BIND_IP setting can be used
- Only one address or name may be specified in VPS_BIND_IP
- In mixed stack platforms, configure the server to accept SA connections on both IPv4 and IPv6 by setting VPS_BIND_IP=::
- In separate stack platforms, the server can only accept SA connections over one of IPv4 or IPv6, not both

Mux config in dual and separate stack OS
- By default, Mux serves clients on all IPv4 addresses available to it
- In order for Mux to serve on IPv6, the default should be overridden
- The Admin pages > Connectivity page
- The sametime.ini settings:
VPMX_DISABLE_CONFIGURATION_UPDATE,
VPMX_HOSTNAME, VPMX_PORT,
VPHMX_HOSTNAME, VPHMX_PORT
- Use a comma separated list for multiple values, For example: VPMX_HOSTNAME=::,0.0.0.0
- Dual stack platforms - ::,0.0.0.0 vs. 0.0.0.0,::
- Standalone Mux and these settings

Known limitations
- Mixing of IPv6 with pre-ST8.0.2 is not supported (backward compatibility only while IPv6 is not used). You have to first gradually shift your whole infrastructure and clients to ST8.0.2, and only then enable IPv6.
- Sametime IPv6 is not supported with Domino 7. This partially derives from incomplete IPv6 support in JRE 1.4.
- Serving on link-local addresses (fe80::/16) is not supported on Linux. You may be able to rely on link-local addresses, but the product does not support their use out of the box.

Best Practices – pure IPv6
- Make sure the DNS and LDAP servers are configured to serve over IPv6
- Make sure all server and client machines are set up properly to use the IPv6 DNS servers
- Configure Domino and Sametime meeting server on the server machine to use IPv6
- Use the UCM_RESOLVE_PREFERRED_IP_VER (sametime.ini) and java.net.preferIPv6Addresses (Java system properties) settings to prefer IPv6
- If the host name on the server machines resolves to more than 1 address, use the UCM_LOCAL_IP and VPS_HOST settings
- Configure Mux to serve on :: (or specific IPv6 addresses) only

Best Practices – mixed IPv6/IPv4
- Make sure the DNS and LDAP servers are configured to serve over IPv6 and IPv4
- Make sure all server and client machines are set up properly to use accessible DNS servers
- Make sure IPv4 DNS servers return IPv4 addresses only (to avoid confusing existing applications)
- Configure Domino and Sametime meeting server on the server machine to use IPv6 and IPv4
- Use the UCM_RESOLVE_PREFERRED_IP_VER (sametime.ini) and java.net.preferIPv6Addresses (Java system properties) settings to prefer IPv4
- If the host name on the server machines resolves to more than 1 address, use the UCM_LOCAL_IP and VPS_HOST settings, choosing the IPv4 addresses
- Configure Mux to serve on ::,0.0.0.0 (or specific addresses)

Troubleshooting
- Consider the whole Sametime community network (servers, muxes, GWs, clients, etc.)
- If IPv6 is used, make sure all components are ST8.0.2 or later
- Check communityConfig.txt on each server to verify the addresses this server uses
- Check sametime.log, sametime.ini and stconfig.nsf to verify the addresses muxes use
- Check the DNS servers and DNS configuration of server machines
- System tools such as ipconfig/ifconfig and netstat can help getting an idea about the IP addresses in use
- System tools such as dig, nslookup or ping can help checking how names resolve to addresses, and weather remote addresses are accessible
- System tools such as telnet and netcat can help checking whether a specific port in a local or remote host is accessible

Validation
- All host names and IP addresses used in sametime.ini and stconfig.nsf are accessible through ping and resolve immediately
- All server processes are up
- No unexplained “rejecting” or “logged out” messages are present in sametime.log
- Use of netstat shows all servers and muxes are listening on the correct addresses
- Use of netstat show all servers are connected to each other and muxes are connected to the correct servers
- Users can login and use the basic functionality
- Users connected through IPv4 and IPv6 can see each other (if a mixed configuration)
- Uses logged in to different servers (and in mixed protocols, if a mixed configuration) can see each other

Available Documentation
- Sametime 8.0.2 documentation (http://publib.boulder.ibm.com/infocenter/sametime/v8r0/index.jsp)
- IPv6.org http://www.ipv6.org
- RFC 2373, RFC 2732 and other documents in http://www.faqs.org
- Domino 8.0.x documentation on IPv6
- DNS and LDAP documentation on IPv6
- OS vendor documentation on networking and IPv6