5G industry news

Packet routing for the other two corners

  • 2 minute read
  • Published by John Grant on 17 May 2018
  • Last modified 17 Dec 2018

The first implementations of 5G are concentrating on the "enhanced mobile broadband" corner of the 5G triangle, using new radio with the existing TCP/IP-based core network technology. But to serve the other two corners, and also address problems operators have had with the current system, a radical change to the way packets are routed is needed, and a group in ETSI, the Industry Specification Group for Next Generation Protocols (ISG NGP) is working on new technology targeted at 3GPP Release 17.

Many of the design decisions made when TCP/IP was first developed, some forty years ago, are no longer appropriate. Memory is no longer a scarce resource, so the network can keep more information about packet flows and less has to be carried in the packets themselves. Line speeds have increased more than processing speeds, so switches now have a data plane, implemented in hardware, to forward the packets, and a separate control plane, implemented in software, which makes the routing decisions; the forwarding process is controlled by a "routing table" which is written by the control plane.

There are two main features of the new technology that are different from the existing system. Firstly, packet headers are greatly simplified, containing only the packet size and a "label" which is a reference to the routing table entry; all other information is carried by control plane messages. These messages can carry much more information than could reasonably go into packet headers, allowing the system to be made much more secure and easier to manage. Where the Sockets API is used, the control plane messages are exchanged when the connect() call is made; with the more modern API proposed by the IETF TAPS group, it is when the Initiate or Rendezvous call is made.

Secondly, there is a separate service for continuous media including audio, video, and new services (such as tactile) proposed for 5G. This is synchronised so that it easily delivers the lowest possible latency, and on wired links the two services are multiplexed together with the traditional packet service using all the capacity that is not occupied by the synchronised service.

More details of ISG NGP and its technology are available here and a detailed technical presentation is here (PDF, 12MB). We also have an informal group within UK5G; click here to request access to its on-line Basecamp project.