LTE is a 4G Mobile Specification for Multimedia.
It has come a long way since the first generation in 79!
Data and voice networks were completely separated since their creation.
Mobile networks were in very early stages of development, and the first commercially automated cellular network (the 1G) was launched in Japan by NTT in 1979, initially in the metropolitan area of Tokyo.
In the 80s, data networks were using packet switching technology like X.25 and voice networks were using circuit switching networks with PABX.
UUCP was a popular protocol to interconnect UNIX systems. It was not a piece of cake to manage and was basically an asynchronous communication. The Internet was mostly used by universities and by the research community. I remember requesting the forms to get access to the Internet for my company and I recall that you had to sign a form admitting that you would not use the Internet for any commercial purpose!
At the end of the 80s, data and voice networks started their convergence.
With the 90s, some digital lines replaced the circuit switched analog technology. ISDN became the best of the switched circuit for telephony and expensive network access, and also used as backup for leased lines.
At that time, there was a battle for the technology that would support data, voice, video and any real-time traffic. Since X.25 could not support this convergence, many people were introducing ATM as the solution.
The network infrastructure, with the minimum speed of 155 Mbps for the trunk lines, and even more required by ATM, were not yet widely available. There was the same problem with the ATM switches which were still very expensive devices, as the ASIC to work with the 53 bytes cells were not yet widely available components.
Waiting for ATM wide availability, frame-relay, a lightweight version of X.25 was the interim solution to fill in the gap with X.25. Frame-relay was the first network that was really able to support both data and voice traffic. Voice over frame relay became very popular thanks to FRF.12 fragmentation. CISCO was a very active member of both the ATM forum and frame-relay forum.
At this time, no one or very few would have bet on VoIP! The ATM scientists were sure that they were on the right path for the future of converged networks and the VoIP supporters were not taken seriously. The IBM choice was to replace the token-ring with ATM 25Mbps for LAN access. IBM was also promoting SNA LU6.2 with APPN for peer-to-peer applications. This was the last IBM attempt to sell SNA as the solution for networking. After this they just followed everybody with TCP/IP.
Also happening at the same time, IPv4 addresses were increasingly consumed and many people were looking for the IPv4 successor. CLNS from the OSI protocols with its NSAP address up to 20 bytes, 160 bits long was the best candidate. Digital adopted OSI for DECNET Phase V. ISIS, its routing protocol, the OSI version of OSPF became very popular with the ISPs, as it was an integrated routing protocol capable to concurrently build CLNS and IP routing tables. Novell ported ISIS to announce IPX routes and SAP services and called this protocol NLSP.
The IETF was still working on IPv6 at this time and RFC2460 was only published in 1998. In the meantime, NAT was keeping the Internet business growing.
In 1998 I was very proud to teach the 5 day CISCO ATM Training, CATM. It was so much fun but at the end of each session I was talking with some students convinced that the future would be Gigabit Ethernet and IP! They were feeling that ATM was too complex and LANE will not scale. They were right but ATM with its UNI, PNNI, LANE, NHRP and all the rest was such a pleasure for a geek that I was also very enthusiastic about it! In the next room, a colleague was teaching the IPv6 course and for me IPv6 was pure Science Fiction!
It was also at the end of the 90s that Cisco introduced TAG Switching which became MPLS after standardization. Most service providers started to study the migration to a new MPLS backbones, as MPLS-VPN enabled sharing a PE with many customers instead of having a dedicated router for each customer.
It is only in 2001, that 3G (Third Generation) was launched, again in Japan by NTT DoCoMo on the WCDMA standard. 3G was the first standard allowing web surfing the Internet from a mobile phone providing access to multimedia content.
No one was using ATM for voice, video or data as planned, but ATM was still popular with service providers. Service providers had two layers of Networks: A WAN backbone allowing them to configure ATM, frame-relay or even X.25 links for customer access or some higher speed links to build their MPLS backbone.
But also at this time, people were starting to realize that ATM looked better on paper than in the real life! ATM was hitting its first big scalability issues. Some big LANE sites were collapsing under the traffic, because the BUS was not able to replicate the broadcast and multicast.
Soon it became obvious that ATM would not work with multi-gigabit networks and VoIP was now considered as the solution for converged networks. ATM was slowly replaced everywhere by all-IP networks with POS or faster, and faster Ethernet links running 10Mbps, 100Mbps, 1Gbps, 10Gbps and now 100Gbps!
In the very early 2k, John Chambers predicted than in about 10 years, people would not pay for voice traffic anymore. This is exactly what happened in France with ADSL and later with fiber. Most people pay a flat rate for Internet access, television and unlimited telephone over IP, now including mobile too.
IPv6 became a reality at the end of the 90s. Mobility support for IPv6 (rfc3775, June 2004) enhanced the IPv4 version and permitted an IPv6 node to roam across any IPv6 subnets without changing its address. The mobile node always seems to be connected to its home link while the user is actually visiting many subnets. This is the condition needed to keep transport connections up without having to restart the application when you move!
With more and more connected people, smartphones, improved support of mobility and more, IPv6 became the key for the next generation of mobile networks. 4G and Long Term Evolution (LTE) rely on IPv6 to provide enough addresses, and to support mobility.
LTE is a 4G mobile specification for multimedia application designed to provide multi-megabit bandwidth, more efficient use of the radio networks, latency reduction and improved mobility.
LTE aims at providing:
- Up to 300 Mbit/s in the downlink
- 75 Mbit/s in the uplink
- one-way latency less than 5 ms between terminal and base station
- handover in less than 1 RTT
- reduced cost in network deployment
In the heart of LTE is mobile support for IPv6 and more precisely Proxy Mobile IPv6 (rfc5213). A proxy mobility agent performs signaling on behalf of a mobile device (MN) attached to the network.
Two new network functions are defined in PMIPv6:
- The Local Mobility Anchor (LMA)
– Provides the home agent function within a PMIPv6 domain, being the topological anchor point for the mobile node’s care-of address.
- The Mobile Access Gateway (MAG)
– A function of an access router responsible for triggering the mobility-related signaling on behalf of the attached mobile device.
LTE Initialization is following:
- The MN enters the PMIPv6 domain and attach to an access-link.
- The MAG verifies the MN Identity and Authorizations.
- If OK, the MAG helps the MN to get all the configuration: address, default gateway,…
- The MN considers the PMIPv6 domain as a link
- The MN sends a RS (Router Solicitation) to the MAG.
- For updating the LMA about the MN location, the MAG sends a PBU (Proxy Binding Update) to the MN’s LMA.
- The LMA sends a PBA (Proxy Binding Acknowledgement) including the MN home network prefixes. It creates the Binding Cache entry and sets up its endpoint of the bi-directional tunnel to the MAG.
- The MAG sends a RA: Router Advertisement to the MN. The MAG can emulate the MN’s Home Link
- The MN can be configured using SLAAC or DHCPv6
- Then the MAG keeps an eye on the Mobile Node and trigger the mobility-related signaling on behalf of the Mobile Node. It is as simple as that!
PBA/PBU Signaling must be protected with IPSec! Data Protection is Optional
Cisco, today, offers a mobile gateway on its 7600 series routers by way of the Service and Application Module for IP (SAMI). But they will not be LTE gateway capable until LTE specific software is available for it. Whatever the case is, Cisco calls themselves LTE Ready, though their SAMI is incomplete solution.
About the author:
Fred Bovy, CCIE # 3013, is a Fast Lane Instructor and Networking Expert consultant with more than 20 years of experience. For the past 10 years, Fred has been working on IPv6 and Service Provider issues. As an IPv6 IOS dev-test Engineer for Cisco, Fred developed a strong expertise with features like 6PE, 6VPE, Netflow for IPv6 and SEND, and performed dev-testing for all these features. Fred wrote the test plans and the TCL Scripts for automating the features testing, and has a deep, code-level understanding of IPv6. In the classroom, Fred inspires his students by bringing in his extensive experience with designing, optimizing and troubleshooting IPv6 for Service Providers and Enterprises.