OmniSGW Operations Guide

OmniSGW - Serving Gateway (SGW)

by Omnitouch Network Services

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Table of Contents

1. Overview
2. Architecture
3. Network Interfaces
4. Key Concepts
5. Getting Started
6. Configuration
7. Web UI - Real-Time Operations Dashboard
8. Monitoring & Metrics
9. Detailed Documentation
10. Additional Resources
11. Contributing
12. Support

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Overview

OmniSGW is a high-performance Serving Gateway (SGW) implementation for 3GPP LTE Evolved Packet Core (EPC) networks, developed by Omnitouch Network Services. It manages the functions for UE mobility and bearer management, including:

• Session Management - Creating, modifying, and terminating UE (User Equipment) data sessions
• Mobility Coordination - Handling handovers between eNodeBs with data forwarding
• Bearer Management - Creating and modifying dedicated bearers for different QoS requirements
• Charging Information - Tracking session events for offline charging
• User Plane Coordination - Controlling the SGW-U (User Plane) for packet forwarding

What SGW-C Does

• Accepts session requests from MME via S11 interface (GTP-C)
• Coordinates with PGW-C for PDN connectivity via S5/S8 interface (GTP-C)
• Manages bearer lifecycle including creation, modification, and deletion
• Programs forwarding rules in SGW-U via Sxa interface (PFCP)
• Handles UE mobility by managing handovers between eNodeBs
• Provides downlink data paging for suspended sessions
• Tracks charging information for offline billing systems

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Architecture

Component Overview

Process Architecture

SGW-C is built on Elixir/OTP and uses a supervised process architecture:

• Application Supervisor - Top-level supervisor managing all components
• Protocol Brokers - Handle incoming/outgoing protocol messages (S11, S5/S8, Sxa)
• Session Processes - One GenServer per active UE session
• Registries - Track allocated resources (TEIDs, SEIDs, Charging IDs, etc.)
• PFCP Node Manager - Maintains PFCP associations with SGW-U peers

Each component is supervised and will automatically restart on failure, ensuring system reliability.

Real-time system health metrics can be monitored via the Web UI Application page:

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Network Interfaces

SGW-C implements three primary 3GPP interfaces:

S11 Interface (GTP-C v2)

Purpose: Control plane signaling between MME and SGW-C

Protocol: GTP-C Version 2 over UDP

Key Messages:

• Create Session Request/Response
• Delete Session Request/Response
• Modify Bearer Request/Response
• Create Bearer Request/Response
• Delete Bearer Request/Response
• Downlink Data Notification/Acknowledge

Configuration: See S11 Interface Documentation

Sxa Interface (PFCP)

Purpose: Control plane signaling between SGW-C and SGW-U

Protocol: PFCP (Packet Forwarding Control Protocol) over UDP

Key Messages:

• Association Setup Request/Response
• Session Establishment Request/Response
• Session Modification Request/Response
• Session Deletion Request/Response
• Session Report Request/Response
• Heartbeat Request/Response

Configuration: See PFCP/Sxa Interface Documentation

S5/S8 Interface (GTP-C v2)

Purpose: Control plane signaling between SGW-C and PGW-C for PDN connectivity

Protocol: GTP-C Version 2 over UDP

Key Messages:

• Create Session Request/Response
• Delete Session Request/Response
• Modify Bearer Request/Response
• Create Bearer Request/Response
• Delete Bearer Request/Response

Configuration: See S5/S8 Interface Documentation

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Key Concepts

UE Session

A UE Session represents an active mobile device connected to the network. Each session manages:

• IMSI (International Mobile Subscriber Identity) - Unique subscriber identifier
• GUTI (Globally Unique Temporary Identifier) - Temporary UE identifier from MME
• MSISDN - Mobile phone number
• TAI (Tracking Area Identifier) - Current location area
• Session TEIDs - Tunnel endpoint identifiers for S11 and S5/S8
• Active Bearers - List of associated data bearers

PDN Connection

A PDN (Packet Data Network) Connection represents a UE's data connection through a specific PGW-C. Each session has:

• APN (Access Point Name) - Identifies the external network
• Charging ID - Unique identifier for billing across SGW and PGW
• TEID (Tunnel Endpoint ID) - S5/S8 interface tunnel identifier
• SEID (Session Endpoint ID) - Sxa interface session identifier
• Default Bearer - Created with every PDN connection
• Dedicated Bearers - Additional bearers for specific QoS needs

Bearer Context

A bearer represents a traffic flow with specific QoS characteristics:

• Default Bearer - Created with every PDN connection for best-effort traffic
• Dedicated Bearers - Additional bearers for specific service requirements (voice, video, etc.)
• EBI (EPS Bearer ID) - Unique identifier for each bearer within a session
• QoS Parameters - QCI (QoS Class Identifier), ARP (Allocation & Retention Priority), bitrates (MBR, GBR)

PFCP Rules

The SGW-C programs the SGW-U with packet processing rules:

• PDR (Packet Detection Rule) - Matches packets (uplink/downlink)
• FAR (Forwarding Action Rule) - Specifies forwarding behavior
• QER (QoS Enforcement Rule) - Enforces bitrate limits
• BAR (Buffering Action Rule) - Controls packet buffering during handovers

See Sxa Interface Documentation for details.

Mobility & Handover

SGW-C supports UE mobility across eNodeBs:

• Intra-MME Handover - Handover within same MME (no SGW change)
• Inter-MME Handover - Handover between MMEs with SGW relocation
• Data Forwarding - Buffering and forwarding data during handover
• Tracking Area Update - UE re-registration when moving between areas

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Getting Started

Prerequisites

• Elixir ~1.16
• Erlang/OTP 26+
• Network connectivity to MME, SGW-U, and PGW-C
• Understanding of LTE EPC architecture

Verifying Operation

Check the logs for successful startup:

[info] Starting OmniSGW...
[info] Starting Metrics Exporter on 127.0.0.40:42068
[info] Starting S11 Broker on 127.0.0.10
[info] Starting S5/S8 Broker on 127.0.0.15
[info] Starting Sxa Broker on 127.0.0.20
[info] Starting PFCP Node Manager
[info] OmniSGW successfully started

Access metrics at http://127.0.0.40:42068/metrics (configured address).

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Configuration

All runtime configuration is defined in config/runtime.exs. The configuration is structured into several sections:

Configuration Overview

Quick Configuration Reference

Section	Purpose	Documentation
metrics	Prometheus metrics exporter	Monitoring Guide
s11	GTP-C interface to MME	S11 Config
s5s8	GTP-C interface to PGW-C	S5/S8 Config
sxa	PFCP interface to SGW-U	Sxa Config

See the Complete Configuration Guide for detailed information.

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Web UI - Real-Time Operations Dashboard

OmniSGW includes a built-in Web UI for real-time monitoring and operations, providing instant visibility into system status without needing command-line tools or metrics queries.

Accessing the Web UI

http://<omnisgw-ip>:<web-port>/

Available Pages:

Page	URL	Purpose	Refresh Rate
UE Sessions	/ue_sessions	View all active UE sessions and bearers	2 seconds
PFCP Sessions	/pfcp_sessions	View PFCP sessions with SGW-U	2 seconds
SGW-U Status	/sgwu_status	Monitor PFCP peer associations	2 seconds
Logs	/logs	Real-time log streaming	Live

Key Features

Real-Time Updates:

• All pages auto-refresh (no manual reload needed)
• Live data streaming from OmniSGW processes
• Color-coded status indicators (green/red)

Search & Filter:

• Search sessions by IMSI, GUTI, phone number
• Instant filtering without page reload

Expandable Details:

• Click any row to see complete session details
• Inspect all active bearers and QoS parameters
• View peer configuration and capabilities

No Authentication Required (Internal Use):

• Direct access from management network
• Designed for NOC/operations team use
• Bind to management IP only for security

Operational Workflows

Session Troubleshooting:

1. User reports connectivity issue
2. Open UE Sessions page
3. Search by IMSI or phone number
4. Verify session exists and has correct:
   - Tracking Area
   - Active bearers and their QoS
   - Tunnel endpoints established
   - Correct PGW-C association
5. If no session found → Check logs for rejection reason

System Health Check:

1. Open SGW-U Status page → Verify all SGW-U peers "Associated"
2. Open UE Sessions → Check active session count vs. capacity
3. Monitor bearer distribution across APNs

Capacity Monitoring:

• Glance at UE Sessions count
• Compare to licensed/expected capacity
• Identify peak usage times
• Monitor distribution by service type

Web UI vs. Metrics

Use Web UI for:

• Individual session and bearer details
• Real-time peer status
• Quick health checks
• Troubleshooting specific users
• Verifying configuration

Use Prometheus Metrics for:

• Historical trends
• Alerting and notifications
• Capacity planning graphs
• Performance analysis
• Long-term monitoring

Best Practice: Use both together - Web UI for immediate operations, Prometheus for trends and alerts.

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Monitoring & Metrics

In addition to the Web UI, OmniSGW exposes Prometheus-compatible metrics for monitoring:

Available Metrics

• Session Metrics

  • teid_registry_count - Active S11/S5S8 TEIDs
  • seid_registry_count - Active PFCP sessions
  • charging_id_registry_count - Active charging IDs
  • active_ue_sessions - Total active UE sessions
  • active_bearers - Total active bearers across all sessions

• Message Metrics

  • s11_inbound_messages_total - GTP-C messages received on S11
  • s5s8_inbound_messages_total - GTP-C messages received on S5/S8
  • sxa_inbound_messages_total - PFCP messages received
  • Message handling duration distributions

• Error Metrics

  • s11_inbound_errors_total - S11 protocol errors
  • s5s8_inbound_errors_total - S5/S8 protocol errors
  • sxa_inbound_errors_total - Sxa protocol errors

Accessing Metrics

Metrics are exposed via HTTP at the configured endpoint:

curl http://127.0.0.40:42068/metrics

See Monitoring & Metrics Guide for dashboard setup and alerting.

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Detailed Documentation

This section provides a comprehensive overview of all OmniSGW documentation. Documents are organized by topic and use case.

Documentation Structure

OmniSGW Documentation
├── OPERATIONS.md (This Guide)
│
└── docs/
    ├── Configuration & Setup
    │   ├── configuration.md          Complete runtime.exs reference
    │
    ├── Network Interfaces
    │   ├── sxa-interface.md          Sxa/PFCP (SGW-U communication)
    │   ├── s11-interface.md          S11 (MME communication)
    │   └── s5s8-interface.md         S5/S8 (PGW-C communication)
    │
    └── Operations
        ├── session-management.md     UE session lifecycle
        ├── bearer-management.md      Bearer operations
        ├── cdr-format.md             Offline charging records
        └── monitoring.md             Prometheus metrics & alerting

Documentation by Topic

🚀 Getting Started

Document	Description	Purpose
OPERATIONS.md	Main operations guide (this document)	Overview and quick start

⚙️ Configuration

Document	Description
configuration.md	Complete runtime.exs configuration reference

🔌 Network Interfaces

Document	Description
sxa-interface.md	PFCP/Sxa interface to SGW-U
s11-interface.md	GTP-C S11 interface to MME
s5s8-interface.md	GTP-C S5/S8 interface to PGW-C

📊 Operations & Monitoring

Document	Description
session-management.md	UE session lifecycle and operations
bearer-management.md	Bearer creation, modification, deletion
cdr-format.md	Offline charging data record format
monitoring.md	Prometheus metrics, Grafana dashboards, alerting

Reading Paths

For Network Operators

1. OPERATIONS.md - Overview (this document)
2. configuration.md - Setup
3. monitoring.md - Monitoring
4. session-management.md - Day-to-day operations

For Network Engineers

1. OPERATIONS.md - Architecture overview (this document)
2. sxa-interface.md - User plane control
3. s11-interface.md - Mobile management
4. s5s8-interface.md - PDN connectivity
5. session-management.md - Session lifecycle
6. bearer-management.md - Bearer operations

For Configuration & Deployment

1. configuration.md - Complete reference
2. monitoring.md - Set up monitoring

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Additional Resources

3GPP Specifications

Spec	Title
TS 29.274	GTP-C v2 (S11 and S5/S8 interfaces)
TS 29.244	PFCP (Sxa interface)
TS 32.251	Packet Switched domain charging
TS 32.298	CDR encoding
TS 23.401	EPC architecture