IPv6: the New Y2K Problem for Backhaul

in Blog, Backhaul, IPv6, LTE

First introduced by Vint Cerf and Bob Kahn in 1974 and now evolved into its fourth version, the Internet Protocol (IPv4) has spread as the main packet switching technology worldwide. Inventions give response to requirements and needs typical of the era in which they are introduced, and the dynamic evolution of today’s society sets ever-shorter expiry dates for these inventions. Several organizations around the world, such as Asia Pacific Network Information Center (APNIC) and National Telecommunications and Information Administration (NTIA) in the US, have recently warned that IPv4 could reach the end of its lifecycle by late 2011, just as it is set to finally win the battle against circuit switching technologies.

The adoption of IP as the basis for new mobile technologies is exhausting IP addresses, since each single device on an IP network needs at least one address to exchange IP packets (or datagrams as they are technically named). The problem gets even worse if we consider M2M applications will cause the number of mobile devices to surge. This IP address exhaustion was already envisioned years ago, when IPv6 was developed as a solution. This new version of the protocol extends the IP address size from 32 bit to 128 bit, increasing the available pool from 4 billion to 340 undecillion (3.4×1038) addresses.

IPv6 is not directly compatible with IPv4: IPv4-only and IPv6-only nodes cannot communicate with each other. However both IP versions can share the same network simultaneously, with three main options generally proposed to implement this coexistence: dual stack (all nodes are given both IPv4 and IPv6 addresses); Network Address Translation (NAT, a single IPv4 address is shared among several nodes); and tunneling (IPv6 packets carried inside IPv4 packets at first and vice versa later).

Maravedis was surprised to learn that, according to the key wireless backhaul vendors interviewed for our recent report, “Wireless Backhaul Market from an All-IP Perspective,” they are not being asked by operators to provide IPv6 capability sooner than in a future upgrade. Considering operators usually want to minimize maintenance on backhaul links after installation, I do not understand why they are risking performance problems when forced to migrate to IPv6. LTE deployment is a good opportunity to upgrade to IPv6, although only a handful of operators are addressing this, such as Comcast, Verizon Wireless, China Telecom, and China Mobile.

Since the trend is to deploy layer-2 Ethernet backhaul, how can layer-3 migration to IPv6 affect the situation? IP migration is relevant to Ethernet backhaul in both management and data planes. In the management plane, each backhaul device requires one IP address in order to be configured and monitored. Remote control of network devices is not a secondary need for operators, since they could see their whole network go down if they were unable to properly manage it. Of the three migration options presented above, dual stack is the only one that requires additional functionality to be embedded into backhaul equipment, since the remaining two (NAT and tunneling) are done with external network nodes and would be consequently transparent in terms of backhaul.

On the other hand, influence of IPv6 on the data plane is not as evident, since IP packets are just the payload for Ethernet backhaul links (they do not implement IP routing). However, implementation of QoS features requires backhaul equipment to look at certain IP packet fields in order to prioritize services. Since datagram fields are differently organized by both versions of the protocol, QoS mechanisms designed for IPv4 are not directly reusable with IPv6 traffic. Furthermore, if IPv6 on IPv4 tunneling is used, the system must somewhat translate priority information from IPv6 header to the IPv4 so that QoS is preserved. 

Although it seems that we are facing a new version of the Y2K-scenario, we remain confident that mobile operators will react in time to reduce its potential affect to a similarly low impact as we saw back in the original scenario in 2000.

MARAVEDIS is a leading analyst firm focusing on 4G and broadband wireless technologies and markets. 

Author: By Esteban Monturus, Market Analyst - Europe & Backhaul 

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