Friday, August 21, 2015

A Primer on IPv4 Scarcity

Philipp Richter (TU Berlin/ICSI) , Mark Allman (ICSI) , Randy Bush (Internet Initiative Japan) , Vern Paxson (UC Berkeley/ICSI)


The IPv4 scarcity became reality since today only about 2% IPv4 addresses are available. The authors tried to answers these questions.
What is IPv4 scarcity?
What factors affect it?
What challenges does it pose?
How are we dealing with it?
To answer these questions, the authors first outline the evolution in address space management as well as address space use patterns,  identifying key factors of the scarcity issues. Finally, they characterize the possible solution space to overcome these issues.

The authors started the evolution of IPv4 address management and checked the degree to which allocation reflects actual use. They categorize history of IPv4 address into three time phases. First is "Early Registration phase". In this time, Address blocks were allocated quite informally, which caused heavy internal fragmentation and waste of address space. Second phase is "Needs-Based Provision". The modern framework of Regional Internet Registries (RIRs) was established in this phase. The primary goal of this phase is the conservation of address space and to get address space, the requester justify their need for the address space. Last phase is "Depletion and Exhaustion Phase". In this phase, more strict allocation policies were applied due to the small last remaining blocks.

During these three phases, the address space are almost fully exhausted.  However, according to "Figure 4. Allocated and routed address blocks", Large amounts of address space are not routed. More specifically, address ranges assigned prior to the existence of the RIRs shows poor utilization, whereas the RIR-allocated ranges show higher utilization, which means that policies to allocate IPv4 are effective.




The scarcity of IPv4 address makes people to think IP address as a virtual resource. People thought IPs are "for free" for last 30 years, but now IPs are valuable resource and became goods exchanged on markets.So, IPv4 address space transfer arise via RIR transfer policies and transfers outside the RIRs and network operators have already started buying and selling address blocks. However, defining the boundaries of what exactly an address transfer is and what it is not is not straightforward. Thus, the authors mentioned IP block transfer is more careful and needs further research.

Finally, the authors consider three possible solution to overcome IPv4 scarcity. First is to use IPv6  address space more. Considering the number of possible addresses with IPv6, this is ultimate nature solution. However, there is an issue that IPv6 is not compatible with IPv4 and complex transition mechanisms between IPv6 and IPv4 are required. Second is to multiplex current IPv4 address space using address sharing techniques like Carrier-grade NAT (CGN). Final possible solution is more efficiently use of the current IPv4 address space. According to Figure 4, about a third of all Internet address blocks are not routed, and thus not in (at least public) use.  Making more efficient use of address space will require adapting address management policies, guidelines and technologies,  including the difficult (both technically and politically) problem of re-assigning already allocated address blocks.


Q1. In slide 23 page, Can you show a graph in slide 23 page as unit of IP address blocks?
A1. It is in backup slides

Q2. Is the same situation possible in IPv6?
A1. It is possible, but for IPv6, there is no informal allocation and waste of IP addresses like first phase of IPv4.

Q3. Given the price of transferring IP block in slide, do you have an evidence about price to buy ip address block?
A3. It is hard to find prices since only few data is publicsized.


Q4. There are many unrouted IP address. How did you guarantee whether they are used for private IP address or for protected IP address? How many these accounts for?
A4. True. Some companies or governments use them as this purpose.
I can not know exact number. However, I assume they are relatively small.