SGSN and GGSN Dimensioning

In UMTS we continue to use SGSNs and Gateway GPRS Support Node
(GGSN) largely as they are used in standard General Packet Radio Service
(GPRS) and the dimensioning rules that apply in UMTS are similar to
those that apply in GPRS.
The dimensioning limits applicable to an SGSN are generally as follows:
■ Total number of simultaneously attached subscribers
■ Total number active PDP contexts
■ Total number of Gb or Iu-PS interfaces
■ Total number of routing areas
■ Total throughput
It is common to find that the real bottlenecks will involve the total number
of attached subscribers or the total throughput. Of course, the limitations
will vary from vendor to vendor, but typical values will range from
25,000 to 150,000 attached subscribers. As with any technology, these limits
tend to increase over time, so that much higher capacities will be available
in one or two year’s time.
For a GGSN, the typical limitations are the total throughput and the
number of simultaneous PDP contexts. Typical systems of today have limitations
in the order of 100,000 simultaneous PDP contexts, but we can
expect significant capacity enhancements over the coming years.