Meeting the ever-increasing demand for high-speed connectivity is a challenge that every service provider is trying to accomplish, mostly through the deployment of 4G-LTE (News - Alert) networks. Unfortunately, the usage caps and high costs associated with these next-generation networks is a turn-off for some users who have begun relying more on local Wi-Fi networks to stay connected.
Noticing this trend, Alcatel-Lucent (News - Alert) (ALU) as part of its lightRadio ™ wireless broadband portfolio has developed a comprehensive lightRadio Wi-Fi solution that enables service providers to leverage Wi-Fi as an access technology and help them expand their service coverage—all while maintaining customer visibility over their network. With its low cost and use of unlicensed spectrum, Wi-Fi can be a key differentiator in helping wireless and wireline operators launch new services and meet user demand.
When deploying the lightRadio solution, service providers can employ one of two main approaches to connecting end user devices to an integrated Wi-Fi/cellular network:
- Thin Pipe Tunneling
- Fat Pipe Tunneling
These two models were recently discussed in detail in an Alcatel-Lucent application note.
Thin Pipe Tunneling
In a thin pipe tunneling approach, each piece of user equipment (UE) creates an encrypted IP Security (IPsec) tunnel (one for each service) that connects back to the evolved Packet Data Gateway (News - Alert) (ePDG), which then terminates the Wi-Fi-attached UE thin-pipe IPsec sessions.
Alcatel-Lucent points out that the thin pipe tunneling approach inherently provides several challenges:
- Thin pipes can't address the installed base of handsets and other Wi-Fi devices due to the fact that IPsec is not widely supported on today's UEs.
- The user experience can be negatively affected by the latency created when establishing an IPsec session, especially for short sessions.
- IPsec encryption/decryption drains battery life.
- Each packet on the Wi-Fi network creates additional overhead as well as new requirements to support packet fragmentation on the WLAN interfaces.
Fat Pipe Tunneling
Fat pipe tunneling, meanwhile, creates a tunnel between the access point (AP) and the WLAN Gateway, where the AP is responsible for mapping the UE data to that tunnel. As discussed last week, the Alcatel-Lucent 7750 SR, an industry-leading IP service edge router, serves as the WLAN Gateway.
Alcatel-Lucent is a strong proponent of this model because it provides "flexibility, scalability and no new UE requirements," meaning that – unlike thin pipe tunneling – it can address the installed base of UEs.
In addition, the fat pipe model prevents data loss by securing traffic on a hop-by-hop basis. With a thin pipe model, data must be secured end-to-end in IPsec from the UE to the ePDG. The fat pipe approach is also compatible with corporate VPN access, enabling end-to-end encryption.
The three main fat pipe tunneling access methods include:
- Bridged VLAN
- Bridged tunnel
- Routed tunnel
Alcatel-Lucent feels that bridged tunneling with Layer 2 over GRE (L2oGRE) – or Layer 2 virtual private network (VPN) over GRE (L2VPNoGRE) – is the most effective approach.
One key benefit of this method is that the Layer 2 stack is completely agnostic, meaning it can support both IPv4 and IPv6 transmissions. In contrast, a routed tunneling approach requires a complete IPv4 and IPv6 dual stack in the network or the implementation of 4to6/6to4 transition mechanisms. Alcatel says its solution supports both approaches, but stresses that Layer 2 bridged tunneling is "more elegant and scalable."
Additional benefits of Layer 2 fat pipe tunneling include support for wholesale Layer 2 WLAN services – something routed tunneling can't do – and the use of Layer 2-aware Network Address Translation (NAT), which "greatly simplifies Wi-Fi IP address management," says Alcatel-Lucent.
As is so often the case in the deployment of next generation networks (be they wired or wireless) the devil really is in the details and plumbing matters. This is evident in what needs to be considered for connecting end user devices to integrated Wi-Fi/cellular networks as 4G LTE market growth accelerates.
Edited by Peter Bernstein