What Does SGW and PGW Stand For?
In the context of LTE (Long Term Evolution) networks, SGW and PGW are two critical network elements that serve important roles in managing data traffic and user connections. Let me explain both of them to you in detail so you can understand their function and how they interact within the network.
SGW – Serving Gateway
SGW stands for Serving Gateway. It is a key component in the LTE architecture and is responsible for forwarding user data between the eNodeB (evolved NodeB, or base station) and the PGW (Packet Gateway). The SGW has multiple functions, but its primary role is to manage the user plane traffic, which refers to the data being sent or received by the user. In addition to forwarding traffic, the SGW is also involved in:
- Data Forwarding: It forwards the user data from the eNodeB to the PGW and vice versa.
- Mobility Management: The SGW supports mobility management by keeping track of the user’s location in the network. This is particularly important during handovers between different eNodeBs or even when transitioning between different tracking areas.
- Packet Routing: It routes packets between different parts of the LTE core network, ensuring that data reaches its correct destination.
PGW – Packet Gateway
PGW stands for Packet Gateway, and it acts as the gateway between the LTE network and external networks like the internet or other operator networks. The PGW is responsible for managing the bearer paths for user data, which includes setting up, maintaining, and terminating these paths. It plays a crucial role in the user plane by routing packets to/from the external networks and handling the IP addresses. Here’s what the PGW does:
- IP Address Allocation: The PGW assigns an IP address to the UE (User Equipment), allowing the device to communicate over the internet or other data networks.
- Traffic Policing and Charging: The PGW performs traffic policing, ensuring that data usage adheres to the allowed limits. It also collects information for billing and charging purposes.
- Bearer Binding and Management: It manages bearer resources and ensures the data is delivered based on the quality of service (QoS) requirements.
- Interworking with External Networks: The PGW serves as an interface to external IP networks, enabling connectivity to services like the internet, VPNs, and other private networks.
SGW and PGW Interaction
The SGW and PGW work together to provide seamless user data flow in the LTE network. When a user device sends or receives data, the information flows through both gateways:
- The SGW forwards data from the eNodeB to the PGW, and the PGW routes the data to its destination, such as the internet or another network.
- When the user moves to a different location, the SGW handles the mobility management aspect by keeping track of the user’s location. It ensures that the user’s data traffic continues to flow smoothly, even as the user moves between different eNodeBs or tracking areas.
- If the user’s data traffic needs to pass through an external IP network, the PGW ensures the traffic is correctly routed to/from the external network.
In short, while the SGW is responsible for handling the user plane traffic within the LTE network, the PGW connects the LTE network to external data networks, providing the necessary IP routing and connectivity. Together, these components enable the flow of user data and ensure that LTE devices can maintain their internet connectivity while on the move.