1. CGN vs PRR
STATEFUL vs STATELESS

2. What is state? Type 1) NAT binding
Customer ID + Internal IP address + port  external IP address + port
Type 2) Which customer “has” which port

3. Where is Type 1 State? CGN STATEFUL PRR STATELESS NAT local state NAT

4. Where is Type 2 State? Static Port Allocation
PRR allocates static port sets.
No log.
CGN allocates static port sets. No log.
CGN
COMPLETE
STATE
PRR SHARED STATE
Ask 1 port at a time: TCP-SYN / PCP
Static provisioning of n ports
NAT
local state
NAT
NAT
NAT
Local state
NAT
NAT

5. Where is Type 2 State? Dynamic Port Allocation
PRR expires port groups independently.
Coarse grain garbage collection.
CGN expires each port independently.
Fine grain garbage collection.
CGN
COMPLETE
STATE
PRR SHARED STATE
Distributed garbage collection algorithm
Ask 1 port at a time: TCP-SYN / PCP
Ask a group of n ports at a time
NAT
local state
NAT
NAT
NAT
PARTIAL SHARED STATE
NAT
NAT
Keep track of port usage Ask for more if need be, Release unused ports and/or blocks