Hi nanog,
When we build MAN (Metropolitan Area Network), we're basically enable the ip layer communication
between millions of end system - taking into account the number of family, business building PCs,etc.
Recall the scarcity of IPv4 address, I wonder how this huge ip address demand was met in US ?
In my mind, we have the following choices:
1. Build the MAN into a private address network, a class A network 10.x.x.x will be sufficient for
most metropolitan. But the cons is: need PAT/NAT to access public Internet, and that leads to
the potential performance bottleneck.
2. Just wondering, can we use a distributed DHCP system? In this scenario, we can almost convert
the address consuming MAN into a 10 to 1 (or 20 to 1) address pool, which achieve nearly the same
address utilization efficiency of dialup address pool. Cons: don't know the scalability of DHCP, any
comments?
3. Build the MAN into a IPv6 network, and use address conversion at the interconnection point between
v4 and v6. Just an idea, feeling that conversion efficiency between v4-v6 should be better than
NAT/PAT, any support comments?
thanks !
Yu Ning
Recall the scarcity of IPv4 address, I wonder how this huge ip address demand was met in US ?
More than 50% of the IPv4 address space is not yet
allocated, so they aren't so scarce. APNIC should be able
to provide sufficient address space -- but you will need to
give them a plan for your network to explain why you need
so much address space.
In my mind, we have the following choices:
1. Build the MAN into a private address network, a class A network 10.x.x.x will be sufficient for
most metropolitan. But the cons is: need PAT/NAT to access public Internet, and that leads to
the potential performance bottleneck.
One could build the MAN using private addresses, but put
customers in public global addresses, which would mean no need
for NAT/PAT.
As I said above, you should be able to get enough address
space from APNIC by providing documentation for your planned
network.
3. Build the MAN into a IPv6 network, and use address conversion at the interconnection point between
v4 and v6. Just an idea, feeling that conversion efficiency between v4-v6 should be better than
NAT/PAT, any support comments?
Conversion efficiency will not be any different and you
would still need to get enough IPv6 address space.
You should probably start by talking with APNIC about
getting enough IPv4 address space to meet your planned network.
That is the simplest and lowest cost approach.
Best wishes,
Ran Atkinson
rja@extremenetworks.com
Senior Scientist
Extreme Networks
Herndon, VA, USA
In my mind, we have the following choices:
1. Build the MAN into a private address network, a class A network 10.x.x.x will be sufficient for
most metropolitan. But the cons is: need PAT/NAT to access public Internet, and that leads to
the potential performance bottleneck.
Build the network on sequential /24's in the 192.168.x.x range. Makes
routing easier. Using 10.x.x.x addresses leads to people messing up
netmasks and broadcasting all over the network. I've done two city wide
networks this way and it looks good in theory but sucks in practical
applications.
Then, as you need 'public' IP's you can route smaller subnets of public
addresses throughout this network. This also keeps your public servers
limited to ones you know about.. (at least some).
DHCP? You have got to be kidding for a MAN.
Networking philosophy opinions are like bellybuttons, we all have them, we
all like our own, other peoples look funny, and most of them smell bad.
Scarcity? You are aware of how much IPv4 space is reserved for China
and its neighbors, yes? 
-adam
Hint 1: Check a Chinese census.
Hint 2: With the positioning of net 127, it's hard to get a clear shot
at a unallocated /2 prefix 