IPv6 FAQ

Deepak Jain deepak at ai.net
Fri Aug 8 17:53:23 CDT 2008


According to: http://www.netbsd.org/docs/network/ipv6/

     * Larger IP address space. IPv4 uses only 32 bits for IP address 
space, which allows only 4 billion nodes to be identified on the 
Internet. 4 billion may look like a large number; however, it is less 
than the human population on the earth! IPv6 allows 128 bits for IP 
address space, allowing 340282366920938463463374607431768211456 (three 
hundred forty undecillion) nodes to be uniquely identified on the 
Internet. A larger address space allows true end to end communication, 
without NAT or other short term workarounds against the IPv4 address 
shortage. (These days NAT is a headache for new protocol deployment and 
has scalability issues; we really need to decommission NAT networks for 
the Internet to grow further).
     * Deploy more recent technologies. After IPv4 was specified 20 
years ago, we saw many technical improvements in networking. IPv6 
includes a number of those improvements in its base specification, 
allowing people to assume these features are available everywhere, 
anytime. "Recent technologies" include, but are not limited to, the 
following:
           o Autoconfiguration. With IPv4, DHCP exists but is optional. 
A novice user can get into trouble if they visit another site without a 
DHCP server. With IPv6, a "stateless host autoconfiguration" mechanism 
is mandatory. This is much simpler to use and manage than IPv4 DHCP. 
RFC2462 has the specification for it.
           o Security. With IPv4, IPsec is optional and you need to ask 
the peer if it supports IPsec. With IPv6, IPsec support is mandatory. By 
mandating IPsec, we can assume that you can secure your IP communication 
whenever you talk to IPv6 devices.
           o Friendly to traffic engineering technologies. IPv6 was 
designed to allow better support for traffic engineering like diffserv 
or intserv (RSVP). We do not have a single standard for traffic 
engineering yet, so the IPv6 base specification reserves a 24-bit space 
in the header field for those technologies and is able to adapt to 
coming standards better than IPv4.
           o Multicast. Multicast is mandatory in IPv6, which was 
optional in IPv4. The IPv6 base specifications themselves extensively 
use multicast.
           o Better support for ad-hoc networking. Scoped addresses 
allow better support for ad-hoc (or "zeroconf") networking. IPv6 
supports anycast addresses, which can also contribute to service 
discoveries.
           o and more.
     * A cure to routing table growth. The IPv4 backbone routing table 
size has been a big headache to ISPs and backbone operators. The IPv6 
addressing specification restricts the number of backbone routing 
entries by advocating route aggregation. With the current IPv6 
addressing specification, we will see only 8192 routes on the 
default-free zone.
     * Simplified header structures. IPv6 has simpler packet header 
structures than IPv4. It will allow future vendors to implement hardware 
acceleration for IPv6 routers easier.
     * Allows flexible protocol extensions. IPv6 allows more flexible 
protocol extensions than IPv4 does, by introducing a protocol header 
chain. Even though IPv6 allows flexible protocol extensions, IPv6 does 
not impose overhead to intermediate routers. It is achieved by splitting 
headers into two flavors: the headers intermediate routers need to 
examine, and the headers the end nodes will examine. This also eases 
hardware acceleration for IPv6 routers.
     * Smooth transition from IPv4. There were number of transition 
considerations made during the IPv6 discussions. Also, there are large 
number of transition mechanisms available. You can pick the most 
suitable one for your site.
     * Follows the key design principles of IPv4. IPv4 was a very 
successful design, as proven by the ultra large-scale global deployment. 
IPv6 is "new version of IP", and it follows many of the design features 
that made IPv4 very successful. This will also allow smooth transition 
from IPv4 to IPv6.
     * and more.



What I'd like to say is that someone here is playing fast and loose with 
"mandatory" and "required" (or its true for same definitions of 
mandatory or required). A couple of these jumped out at me like, "Only 
8192 routes on the DFZ" and other things.

Rather than jumping down someone's throat here, are these assumptions 
rampant (or even accurate)? We came across this as we were trying to 
enhance our own Ops groups documents to share with customers, and well, 
I don't think we want to share this. ;)

Deepak




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