(MS-SGSN-GGSN) GPRS Interfaces in 2G network

Here, we illustrate the GPRS interfaces between the MS, the SGSN, and the GGSN in 2G network in both 'control plan', and 'data plan'.

  • The 'control plan' is where the signaling messages are passing.
  • While the 'data plan' is where user data is passing.

User Plan interfaces in 2G

Below diagram shows the interfaces exist between the MS and the GGSN in user plan in 2G network,

The BSS means 'Base Station Subsystem'. And it contains the BSC and the BTS.

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MS - GGSN user plan GPRS interfaces in 2G

MS - GGSN user plan GPRS interfaces in 2G

Gn interface

  • SGSNs and GGSNs use the 'Gn interface' in the communication between each other.
  • In case the SGSNs exist in different PLMN than the GGSNs, this interface name will be the 'Gp interface'
  • The protocol stack for Gn/Gp interface shows that it uses TCP/IP in the network packet routing  between different nodes.
  • While, it uses the GTP-U protocol 'GPRS Tunneling Protocol' in the application layer.
  • GTP-U refers to 'GPRS Tunneling Protocol for the user plane', it tunnels user data between the SGSNs and the GGSNs in the user plan.

Gb interface

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  • It is the interface between the BSC and the SGSN. The protocols in this interface are,

Network Service (NS)

  • Responsible for end-to-end communication between the SGSN and the BSC.

BSSGP

  • 'BSS GPRS Protocol', it provides routing,  and QoS related information between the BSC and the SGSN

LLC

  • 'Logical Link Control', it controls logical links between an MS and the SGSN.

SNDCP

  • 'Subnetwork Dependent Convergence Protocol', it controls the transfer of user plan data between the MS and the SGSN.

Um interface

  • The Um interface is the interface between the MS and the BSS.

RLC

  • 'Radio Link Control', it controls the logical links between the MS and the BSS over the radio interface.

Control Plan interfaces in 2G

Below graph shows the control plan interfaces between the MS and the SGSN in in 2G,

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MS - SGSN control plan GPRS interfaces in 2G

MS - SGSN control plan GPRS interfaces in 2G

Gb interface

  • It is the same as the Gb interface in user plan, except the application layer between the SGSN and the MS. The application layer here will use 'GMM/SM' protocol instead of SNDCP.

GMM/SM

The protocol responsible for Mobility Management (MM) and Session Management (SM) functionality between the MS and the SGSN.

Um interface

It is the same as the Um interface in user plan, instead of using 'GMM/SM' from the MS side instead of 'SNDCP'.