VectorCore SGW

VectorCore SGW is an LTE Serving Gateway implementation with separate SGW-C and SGW-U processes. It follows a CUPS design: SGW-C handles GTPv2-C and PFCP control-plane procedures, while SGW-U handles GTP-U forwarding with an eBPF dataplane.

Components

• sgw-c: SGW Control Plane
• sgw-u: SGW User Plane
• sgwctl: configuration validation and runtime inspection tool

Current Feature Set

• CUPS split between SGW-C and SGW-U.
• S11 GTPv2-C toward the MME.
• S5/S8-C GTPv2-C toward the PGW.
• Sxa PFCP between SGW-C and SGW-U.
• S1-U and S5/S8-U GTP-U forwarding on SGW-U.
• eBPF/XDP dataplane for GTP-U TEID match, rewrite, redirect, punt, and drop.
• PFCP-driven PDR/FAR installation and removal on SGW-U.
• Default bearer Create Session, Modify Bearer, Delete Session, and Release Access Bearers handling.
• PGW-initiated Create Bearer handling for dedicated bearers.
• Piggybacked GTPv2-C message handling.
• Multi-PDN and multi-UE bearer ownership isolation by S11 context and EBI.
• GTPv2-C retransmission response caching.
• GTPv2-C transaction collision handling with configurable strict/permissive policy.
• Dynamic GTPv2-C Echo probing and peer health tracking for observed MME and PGW peers, including RTT, missed Echo counters, Recovery IE restart tracking, API visibility, Prometheus metrics, and down-peer procedure warnings.
• PGW restart and S5/S8-C path-failure manager with PGW-to-session indexing, affected-session marking, API visibility, Prometheus metrics, and configurable warning/blocking policy for procedures toward a down PGW.
• MME restoration and Network Triggered Service Restoration handling with MME path/restart tracking, APN/QCI/ARP preserve/delete policy, optional delete-policy cleanup, DDN triggering, DDN Ack/Failure handling, Modify Bearer completion, API visibility, and Prometheus metrics.
• Downlink Data Notification throttling and priority paging controls with per-MME token buckets, per-UE suppression, high-priority IMS/QCI/ARP bypass, MME low-priority throttling enforcement, bounded delayed DDN queue, optional Stop Paging after DDN Ack, API visibility, and Prometheus metrics.
• Static outer IP DSCP marking for SGW-C GTP-C, SGW-C PFCP, SGW-U PFCP, and SGW-U forwarded GTP-U.
• QCI-aware GTP-U outer DSCP marking in SGW-U using operator-configured QCI-to-DSCP mappings.
• 3GPP Release 15 NSA/DCNR awareness for GTPv2-C Secondary RAT Usage Data Report IE capture, owner-scoped session storage, S5/S8-C forwarding, API visibility, and Prometheus counters.
• Recovery counter support.
• JSON API listeners for SGW-C and SGW-U runtime state.
• Prometheus metrics listeners.
• YAML configuration with strict unknown-field rejection.

Build Requirements

• Linux.
• Go 1.26.2 or newer compatible Go toolchain.
• make.
• clang and libbpf development headers for eBPF object generation.
• Kernel/eBPF support for XDP attachment.
• Runtime privileges for SGW-U to attach eBPF programs to network interfaces.

The eBPF bindings are generated with github.com/cilium/ebpf/cmd/bpf2go through go generate.

Build

make clean
make

This builds:

bin/sgw-c
bin/sgw-u
bin/sgwctl

Useful targets:

make test
make vet
make verify
make install
make uninstall

Default install paths:

/opt/vectorcore/bin/sgw-c
/opt/vectorcore/bin/sgw-u
/opt/vectorcore/bin/sgwctl
/opt/vectorcore/etc/sgw-c.yaml
/opt/vectorcore/etc/sgw-u.yaml

Run

Validate configuration:

./bin/sgw-c -c configs/sgw-c.yaml -validate
./bin/sgw-u -c configs/sgw-u.yaml -validate
./bin/sgwctl validate -sgwc configs/sgw-c.yaml -sgwu configs/sgw-u.yaml

Start SGW-U:

./bin/sgw-u -d -c configs/sgw-u.yaml

Start SGW-C:

./bin/sgw-c -d -c configs/sgw-c.yaml

Start SGW-U before SGW-C so the PFCP peer is available when SGW-C starts.

CLI Flags

sgw-c:

-c string      path to SGW-C YAML config
               default: /etc/vectorcore/sgw/sgw-c.yaml
-d             enable debug console logging
-validate      load and validate config, then exit
-v             print version and exit

sgw-u:

-c string      path to SGW-U YAML config
               default: /etc/vectorcore/sgw/sgw-u.yaml
-d             enable debug console logging
-validate      load and validate config, then exit
-v             print version and exit

sgwctl:

validate       validate SGW-C and/or SGW-U config files
dry-run        alias for validate
health         show SGW-C health
sessions       list SGW-C sessions
bearers        list SGW-C sessions with bearer details
pfcp           show SGW-C and SGW-U PFCP association status
gtpc-peers     show SGW-C GTP-C peer health
pgw-failures   show SGW-C PGW path and restart state
recovery       show SGW-C checkpoint and recovery status
bearer-inactivity show SGW-C bearer inactivity cleanup status
idle-downlink show SGW-C idle downlink status and SGW-U GTP-U counters
bpf            show SGW-U BPF map state

Validation example:

./bin/sgwctl validate -sgwc configs/sgw-c.yaml -sgwu configs/sgw-u.yaml

SGW-C Configuration

Default file: configs/sgw-c.yaml

Configuration layout and migration

The canonical SGW-C schema separates transport from optional behavior:

• gtpc: contains S11/S5-C bindings, S11 retransmission timers, transaction handling, and GTP peer health.
• pfcp: contains the local endpoint, heartbeat settings, and SGW-U peers.
• features: contains NSA/DCNR, PGW failure handling, MME restoration, DDN control, idle-downlink notification, session recovery, and bearer-inactivity cleanup.
• qos:, logging:, api:, metrics:, and shutdown: remain independent top-level concerns.

This is a backward-incompatible schema change. Parsing is strict: the former top-level s11: block, feature blocks under gtpc:, flat feature settings, and policy reason: fields are rejected. Validate migrated files with sgw-c -validate or sgwctl validate before deployment.

Old:

gtpc:
  mme_restoration:
    preserve:
      - apn: "ims"
        reason: "preserve IMS PDN for network triggered service restoration"

s11:
  t3_response_seconds: 3
  n3_requests: 5

New:

gtpc:
  s11:
    bind: "sgwinterface"
    timers:
      t3_response_seconds: 3
      n3_requests: 5

features:
  mme_restoration:
    policy:
      preserve:
        # Preserve IMS PDNs for network-triggered service restoration.
        # Generated reason: mme-restoration-preserve-apn-ims
        - apn: "ims"

Policy reasons are generated internally; operators should put human rationale in YAML comments. Codes use <feature>-<action>-<matchers> with matcher fields ordered as APN, QCI, ARP range, bearer type, and idle timeout. Values are lowercased and sanitized. Examples include ddn-high-priority-apn-ims, mme-restoration-delete-apn-internet-qci-9, and bearer-inactivity-cleanup-dedicated-idle-300. Generated codes continue to appear in logs, APIs, session state, and recovery checkpoints. Procedural reasons such as per-mme-rate-limit remain unchanged.

Top-level sections:

sgwc:
  node_id: "sgw-c-1"
  plmn:
    mcc: "311"
    mnc: "435"
  state_dir: "/var/lib/vectorcore-sgw"
  control_plane_ip: "10.90.250.59"

interfaces:
  control:
    sgwinterface:
      listen: "10.90.250.59:2123"

gtpc:
  s11:
    bind: "sgwinterface"
    timers:
      t3_response_seconds: 3
      n3_requests: 5
  s5c:
    bind: "sgwinterface"
  transactions:
    create_bearer_retry_guard:
      enabled: true
    collision_handling:
      mode: "strict"
      active_procedure_timeout_seconds: 120
  peer_health:
    enabled: true
    timers:
      echo_interval_seconds: 30
      echo_timeout_seconds: 3
    thresholds:
      suspect_after_missed: 2
      down_after_missed: 3
      degraded_rtt_ms: 500
    probe:
      mme: true
      pgw: true
    warn_on_down_peer_procedure: true

pfcp:
  local_addr: "127.0.0.1:8805"
  heartbeat:
    interval_seconds: 10
    timeout_seconds: 30
  sgwu:
    - name: "sgw-u-1"
      node_id: "sgw-u-1"
      addr: "127.0.0.2:8805"

features:
  nsa_dcnr:
    enabled: true
    forward_secondary_rat_usage_reports: true
  pgw_failure_handling:
    enabled: true
    detection:
      mark_sessions_on_path_down: true
      mark_sessions_on_restart: true
    actions:
      block_new_procedures_to_down_pgw: false
      notify_mme_on_pgw_restart: false
  mme_restoration:
    enabled: true
    detection:
      mark_sessions_on_path_down: true
      mark_sessions_on_restart: true
    actions:
      enforce_delete_policy: true
      trigger_ddn: true
      cleanup_timeout_seconds: 30
      default_action: "preserve"
    policy:
      preserve:
        - apn: "ims"
        - qci: 1
        - arp:
            priority_min: 1
            priority_max: 3
      delete:
        - apn: "internet"
          qci: 9
  ddn:
    enabled: true
    rate_limit:
      per_mme_per_second: 50
      per_mme_burst: 100
      per_ue_suppression_seconds: 10
    low_priority_throttling:
      honor_mme_throttling: true
      throttle_seconds: 30
      high_priority_bypass: true
    delayed_queue:
      max_entries: 1000
      max_entries_per_mme: 200
      max_age_seconds: 30
    stop_paging:
      enabled: false
      on_ddn_ack: false
    policy:
      high_priority:
        - apn: "ims"
        - qci: 1
        - arp:
            priority_min: 1
            priority_max: 3
      low_priority:
        - apn: "internet"
          qci: 9
  idle_downlink_notification:
    enabled: false
    actions:
      trigger_ddn: true
    conditions:
      require_release_access_drop: true
    throttling:
      report_throttle_seconds: 10
    policy:
      high_priority:
        - apn: "ims"
        - qci: 1
        - arp:
            priority_min: 1
            priority_max: 3
      suppress:
        - apn: "internet"
          qci: 9
  session_recovery:
    enabled: false
    storage:
      backend: "sqlite"
      sqlite_path: "/opt/vectorcore/data/sgwc-db"
    startup:
      restore: true
      reconcile: true
    checkpoint_interval_seconds: 5
  bearer_inactivity:
    enabled: false
    timers:
      check_interval_seconds: 30
      dedicated_bearer_idle_seconds: 300
      pending_bearer_timeout_seconds: 60
      default_bearer_idle_seconds: 0
    conditions:
      require_no_recent_control_activity: true
    actions:
      delete_default_bearers: false
    policy:
      preserve:
        - apn: "ims"
          qci: 5
          bearer_type: "default"
        - qci: 1
      cleanup:
        - bearer_type: "dedicated"
          idle_seconds: 300

qos:
  outer_marking:
    enabled: true
    gtpc:
      enabled: true
      dscp: 40
    pfcp:
      enabled: true
      dscp: 40

logging:
  level: info
  file: /var/log/vectorcore/sgw/sgw-c.log

api:
  listen: "127.0.0.1:8080"

metrics:
  listen: "127.0.0.1:9090"

shutdown:
  timeout_seconds: 5

SGW-C options:

Path	Purpose
sgwc.node_id	SGW-C node identifier.
sgwc.plmn.mcc	MCC for the local PLMN.
sgwc.plmn.mnc	MNC for the local PLMN.
sgwc.state_dir	Directory for persisted runtime state such as the recovery counter.
sgwc.control_plane_ip	IP advertised in SGW-C control-plane F-TEIDs.
interfaces.control.<name>.listen	UDP listen address for a named control interface.
gtpc.s11.bind	Named control interface used for S11.
gtpc.s11.timers.t3_response_seconds	GTPv2-C retransmission timeout for unanswered S11 requests.
gtpc.s11.timers.n3_requests	Maximum S11 retransmission count before transaction failure.
gtpc.s5c.bind	Named control interface used for S5/S8-C.
gtpc.transactions.create_bearer_retry_guard.enabled	Enables repeated Create Bearer retry guard.
gtpc.transactions.collision_handling.mode	GTPv2-C transaction collision policy. strict rejects unsafe overlaps. permissive only relaxes bearer-scoped overlaps when one side has no decoded EBI scope.
gtpc.transactions.collision_handling.active_procedure_timeout_seconds	Timeout for stale active GTPv2-C procedure state. Default 120.
gtpc.peer_health.enabled	Enables SGW-C GTPv2-C peer health tracking and Echo probing.
gtpc.peer_health.timers.echo_interval_seconds	GTPv2-C Echo probe interval. Default 30.
gtpc.peer_health.timers.echo_timeout_seconds	GTPv2-C Echo response timeout. Default 3.
gtpc.peer_health.thresholds.suspect_after_missed	Consecutive missed Echo threshold for suspect state. Default 2.
gtpc.peer_health.thresholds.down_after_missed	Consecutive missed Echo threshold for down state. Default 3.
gtpc.peer_health.thresholds.degraded_rtt_ms	RTT threshold for degraded state. Default 500.
gtpc.peer_health.probe.mme	Enables Echo probing for observed MME GTP-C peers.
gtpc.peer_health.probe.pgw	Enables Echo probing for observed PGW GTP-C peers.
gtpc.peer_health.warn_on_down_peer_procedure	Logs a warning when a procedure starts toward a peer currently marked down.
features.nsa_dcnr.enabled	Enables Release 15 NSA/DCNR awareness in SGW-C.
features.nsa_dcnr.forward_secondary_rat_usage_reports	Forwards S11 Secondary RAT Usage Data Report IEs to the owner PGW session on S5/S8-C Modify Bearer.
features.pgw_failure_handling.enabled	Enables PGW restart/path-failure session marking.
features.pgw_failure_handling.detection.mark_sessions_on_path_down	Marks sessions indexed to a PGW when that PGW transitions down or back up.
features.pgw_failure_handling.detection.mark_sessions_on_restart	Marks sessions indexed to a PGW when that PGW's Recovery IE restart counter changes.
features.pgw_failure_handling.actions.block_new_procedures_to_down_pgw	If true, rejects new PGW-owned S5/S8-C procedures toward a PGW currently marked down. Default false, warning-only.
features.pgw_failure_handling.actions.notify_mme_on_pgw_restart	Reserved for future TS 29.274 PGW Restart Notification support. Must be false in this release.
features.mme_restoration.enabled	Enables MME restoration/NTSR handling.
features.mme_restoration.detection.mark_sessions_on_path_down	Marks sessions indexed to an MME when that MME transitions down or back up.
features.mme_restoration.detection.mark_sessions_on_restart	Marks sessions indexed to an MME when that MME's Recovery IE restart counter changes.
features.mme_restoration.actions.enforce_delete_policy	Enforces delete-policy sessions with S5/S8-C Delete Session and PFCP cleanup. PGW rejection retains local state.
features.mme_restoration.actions.trigger_ddn	Sends S11 Downlink Data Notification for preserved sessions during NTSR.
features.mme_restoration.actions.cleanup_timeout_seconds	Timeout for restoration cleanup and DDN send operations. Default 30.
features.mme_restoration.actions.default_action	Policy action for unmatched sessions. preserve or delete. Default preserve.
features.mme_restoration.policy.preserve[]	Preserve rules matched by APN, QCI, and/or ARP priority range. Preserve rules win over delete rules.
features.mme_restoration.policy.delete[]	Delete rules matched by APN, QCI, and/or ARP priority range.
features.ddn.enabled	Enables DDN throttling and priority paging decisions.
features.ddn.rate_limit.per_mme_per_second	Per-MME DDN token refill rate. Default 50.
features.ddn.rate_limit.per_mme_burst	Per-MME DDN token bucket burst size. Default 100.
features.ddn.rate_limit.per_ue_suppression_seconds	Suppresses duplicate non-high-priority DDNs for the same UE within this window. Default 10.
features.ddn.low_priority_throttling.honor_mme_throttling	Applies MME-provided DDN Ack low-priority throttling to future low-priority DDN decisions.
features.ddn.low_priority_throttling.throttle_seconds	Fallback low-priority throttle duration when the MME throttling IE lacks a usable duration. Default 30.
features.ddn.low_priority_throttling.high_priority_bypass	Allows high-priority DDNs to bypass an empty per-MME token bucket.
features.ddn.delayed_queue.max_entries	Global bound for delayed DDN queue entries. Default 1000.
features.ddn.delayed_queue.max_entries_per_mme	Per-MME bound for delayed DDN queue entries. Default 200.
features.ddn.delayed_queue.max_age_seconds	Maximum age for queued delayed DDN work. Default 30.
features.ddn.stop_paging.enabled	Enables Stop Paging support. Default false until ISR lab validation.
features.ddn.stop_paging.on_ddn_ack	If true, sends Stop Paging after accepted DDN Ack when restoration state proves it is eligible. Requires enabled=true.
features.ddn.policy.high_priority[]	High-priority DDN rules matched by APN, QCI, and/or ARP priority range.
features.ddn.policy.low_priority[]	Low-priority DDN rules matched by APN, QCI, and/or ARP priority range.
features.idle_downlink_notification.enabled	Enables idle downlink packet reporting/DDN trigger flow. Default false until live lab validation is complete.
features.idle_downlink_notification.actions.trigger_ddn	Allows SGW-C to send S11 DDN for accepted idle downlink reports.
features.idle_downlink_notification.throttling.report_throttle_seconds	Per bearer/session idle downlink report throttle. Default 10.
features.idle_downlink_notification.conditions.require_release_access_drop	Limits idle downlink reports to DROP state caused by Release Access Bearers. Default true.
features.idle_downlink_notification.policy.high_priority[]	Idle downlink report rules eligible for DDN, matched by APN, QCI, and/or ARP priority range. Defaults include IMS, QCI 1, and high ARP.
features.idle_downlink_notification.policy.suppress[]	Idle downlink report rules suppressed by policy. Defaults suppress low-priority internet QCI 9.
features.session_recovery.enabled	Enables SGW-C session checkpoint/recovery. Default false until restore/reconcile phases are complete.
features.session_recovery.storage.backend	Checkpoint backend. sqlite is the supported local restart-recovery backend; Redis/etcd are reserved for future HA.
features.session_recovery.storage.sqlite_path	SQLite checkpoint DB path.
features.session_recovery.startup.restore	Reload checkpointed SGW-C session state at startup. Restored sessions must reconcile before becoming active.
features.session_recovery.startup.reconcile	Reconcile restored sessions against SGW-U PFCP/eBPF state at startup. Requires restore=true.
features.session_recovery.checkpoint_interval_seconds	Minimum periodic checkpoint cadence for dirty sessions. Default 5.
features.bearer_inactivity.enabled	Enables bearer inactivity tracking/cleanup. Default false while activity detection and cleanup execution are phased in.
features.bearer_inactivity.timers.check_interval_seconds	Periodic inactivity scan interval. Default 30.
features.bearer_inactivity.timers.dedicated_bearer_idle_seconds	Default idle threshold for dedicated bearers. Default 300.
features.bearer_inactivity.timers.pending_bearer_timeout_seconds	Timeout for pending bearer procedures before they can be considered stale. Default 60.
features.bearer_inactivity.timers.default_bearer_idle_seconds	Default-bearer idle threshold. 0 disables default-bearer inactivity cleanup.
features.bearer_inactivity.actions.delete_default_bearers	Allows default-bearer inactivity cleanup when explicitly paired with a positive default-bearer idle timeout. Default false.
features.bearer_inactivity.conditions.require_no_recent_control_activity	Requires no recent bearer/session control activity before cleanup eligibility. Default true.
features.bearer_inactivity.policy.preserve[]	Preserve rules matched by APN, QCI, bearer type, and/or ARP priority range. Preserve rules are intended to protect IMS signaling, QCI 1, and high-priority sessions.
features.bearer_inactivity.policy.cleanup[]	Cleanup rules matched by bearer type/APN/QCI/ARP. Phase 1 only validates policy; later phases execute cleanup.
pfcp.local_addr	SGW-C PFCP local address.
pfcp.heartbeat.interval_seconds	PFCP heartbeat interval.
pfcp.heartbeat.timeout_seconds	PFCP heartbeat timeout.
pfcp.sgwu[].name	SGW-U peer name.
pfcp.sgwu[].node_id	SGW-U peer node ID.
pfcp.sgwu[].addr	SGW-U PFCP address.
qos.outer_marking.enabled	Enables outer IP DSCP marking.
qos.outer_marking.gtpc.enabled	Enables DSCP marking on SGW-C GTP-C sockets.
qos.outer_marking.gtpc.dscp	GTP-C DSCP value, range 0-63. Default 40.
qos.outer_marking.pfcp.enabled	Enables DSCP marking on SGW-C PFCP sockets.
qos.outer_marking.pfcp.dscp	PFCP DSCP value, range 0-63. Default 40.
logging.level	Log level.
logging.file	Log file path.
api.listen	SGW-C HTTP API listen address.
metrics.listen	SGW-C metrics listen address.
shutdown.timeout_seconds	Graceful shutdown timeout.

Required SGW-C fields include sgwc.node_id, sgwc.plmn.mcc, sgwc.plmn.mnc, gtpc.s11.bind, gtpc.s5c.bind, pfcp.local_addr, and at least one pfcp.sgwu entry.

SGW-C exposes runtime state through its HTTP API listener:

Endpoint	Purpose
/health	SGW-C health response.
/sessions	SGW-C session list.
/sessions/{session_id}	Detailed SGW-C session and bearer state, including PGW failure, MME restoration, and DDN control decision fields.
/gtpc/peers	Observed GTP-C peer health and Recovery IE state.
/gtpc/pgw-failures	PGW path/restart state and affected session counts.
/gtpc/mme-restorations	MME restoration/path/restart state and affected session counts.
/gtpc/ddn-control	DDN throttling, priority paging, token, throttle, delay, suppress, and per-UE state.
/gtpc/idle-downlink	Idle downlink report/DDN status counters.
/pfcp/associations	SGW-C PFCP association state.
/recovery/status	SGW-C checkpoint backend, restore counts, peer Recovery IE restore counts, and current recovery summary.

SGW-U API endpoints include:

Endpoint	Purpose
/sessions	SGW-U PFCP sessions with PDR/FAR state.
/pfcp/associations	SGW-U PFCP association state with SGW-C peers.
/bpf/rules	SGW-U eBPF forwarding rules and per-rule counters.
/gtpu/counters	SGW-U userspace GTP-U counters, including idle downlink hits.

SGW-C exports the following control-plane metrics on its Prometheus listener:

Metric	Purpose
sgwc_gtpv2c_collision_rejections_total	Count of rejected overlapping GTPv2-C procedures by action, policy, active procedure, new procedure, and owner.
sgwc_gtpv2c_collision_stale_expired_total	Count of stale active-procedure records expired before a new collision decision.
sgwc_gtpc_peer_state	One-hot peer health state gauge by role, peer, and state.
sgwc_gtpc_peer_echo_rtt_seconds	Last GTPv2-C Echo RTT by role and peer.
sgwc_gtpc_peer_echo_sent_total	Count of GTPv2-C Echo Requests sent by role and peer.
sgwc_gtpc_peer_echo_responses_total	Count of GTPv2-C Echo Responses received by role and peer.
sgwc_gtpc_peer_echo_timeouts_total	Count of GTPv2-C Echo timeouts by role and peer.
sgwc_gtpc_peer_restarts_total	Count of Recovery IE restart-counter changes by role and peer.
sgwc_pgw_path_state	One-hot PGW path/restart state gauge by PGW and state.
sgwc_pgw_affected_sessions	Current count of sessions affected by PGW path/restart state.
sgwc_pgw_restarts_total	Count of PGW Recovery IE restart-counter changes handled by SGW-C.
sgwc_pgw_path_down_total	Count of PGW path-down transitions handled by SGW-C.
sgwc_mme_restoration_state	One-hot MME restoration/path/restart state gauge by MME and state.
sgwc_mme_restoration_affected_sessions	Current count of sessions affected by MME restoration state.
sgwc_mme_restarts_total	Count of MME Recovery IE restart-counter changes handled by SGW-C restoration.
sgwc_mme_path_down_total	Count of MME path-down transitions handled by SGW-C restoration.
sgwc_ddn_control_tokens	Current per-MME DDN control token count.
sgwc_ddn_control_sent_total	Count of DDN sends allowed by DDN control per MME.
sgwc_ddn_control_delayed_total	Count of DDN delay decisions per MME.
sgwc_ddn_control_suppressed_total	Count of DDN suppress decisions per MME.
sgwc_ddn_control_high_priority_bypassed_total	Count of high-priority DDN bypass sends per MME.
sgwc_ddn_control_low_priority_throttle_active	Gauge showing whether MME low-priority DDN throttling is active.
sgwc_ddn_control_ue_sent_total	Count of DDN sends allowed by DDN control per UE.
sgwc_ddn_control_ue_delayed_total	Count of DDN delay decisions per UE.
sgwc_ddn_control_ue_suppressed_total	Count of DDN suppress decisions per UE.
sgwc_checkpoint_enabled	Gauge showing whether SGW-C session checkpointing is enabled.
sgwc_checkpoint_sessions_loaded	Session snapshots loaded from checkpoint storage at startup.
sgwc_checkpoint_sessions_restored	Session snapshots restored at startup.
sgwc_checkpoint_peer_snapshots_loaded	Peer Recovery IE snapshots loaded at startup.
sgwc_checkpoint_gtpc_peers_restored	MME/PGW Recovery IE snapshots restored at startup.
sgwc_checkpoint_pfcp_peers_restored	SGW-U Recovery Time Stamp snapshots restored at startup.
sgwc_checkpoint_flushes_total	Checkpoint writer flush attempts.
sgwc_checkpoint_flush_failures_total	Checkpoint writer flush failures.
sgwc_checkpoint_session_saves_total	Session snapshots saved by the checkpoint writer.
sgwc_checkpoint_session_deletes_total	Session snapshots deleted by the checkpoint writer.
sgwc_checkpoint_peer_saves_total	Peer Recovery IE snapshots saved by the checkpoint writer.
sgwc_recovery_sessions	Current SGW-C sessions by recovery/session state.
sgwc_pfcp_reconciliation_sessions	Current SGW-C sessions by PFCP reconciliation state.
sgwc_pfcp_repair_plan_sessions	Current SGW-C sessions by PFCP repair plan action.
sgwc_nsa_secondary_rat_usage_reports_captured_total	Count of Release 15 Secondary RAT Usage Data Report IEs captured on S11 by APN and source procedure.
sgwc_nsa_secondary_rat_usage_reports_forwarded_total	Count of Release 15 Secondary RAT Usage Data Report IEs forwarded on S5/S8-C by APN and resulting cause.

Additional transaction collision behavior and validation notes are in docs/gtpv2c-transaction-collision.md.

GTPv2-C peer health behavior and validation notes are in docs/gtpc-peer-health.md.

PGW restart and path-failure behavior and validation notes are in docs/pgw-restart-path-failure.md.

MME restoration/NTSR behavior and live validation notes are in docs/mme-ntsr-lab-validation.md.

DDN throttling and priority paging validation notes are in docs/ddn-control-phase8-validation.md.

Bearer inactivity cleanup behavior and live validation notes are in docs/bearer-inactivity-lab-validation.md.

NSA/DCNR Secondary RAT report behavior and validation notes are in docs/5g-nsa-dcnr-awareness.md.

SGW-U Configuration

Default file: configs/sgw-u.yaml

Top-level sections:

sgwu:
  node_id: "sgw-u-1"

pfcp:
  listen: "127.0.0.2:8805"
  allowed_sgwc:
    - "127.0.0.1"

interfaces:
  user:
    sgwinterface:
      ifname: "eth0"
      listen: "10.90.250.59:2152"

gtpu:
  s1u:
    bind: "sgwinterface"
  s5u:
    bind: "sgwinterface"

qos:
  outer_marking:
    enabled: true
    gtpu:
      enabled: true
      dscp: 0
    pfcp:
      enabled: true
      dscp: 40
  qci_marking:
    enabled: true
    override_default_gtpu: true
    default_gtpu_dscp: 0
    unknown_teid_dscp: 0
    trust_inner_dscp: false
    qci_to_dscp:
      1: 46
      2: 34
      3: 26
      4: 26
      5: 40
      6: 18
      7: 26
      8: 0
      9: 0

dataplane:
  driver_mode: "xdp-generic"
  unknown_teid: "punt"
  attach_on_start: true
  cleanup_on_exit: true
  map_max_entries: 65536

logging:
  level: info
  file: /var/log/vectorcore/sgw/sgw-u.log

api:
  listen: "127.0.0.1:8081"

metrics:
  listen: "127.0.0.1:9091"

shutdown:
  timeout_seconds: 5

SGW-U options:

Path	Purpose
sgwu.node_id	SGW-U node identifier.
pfcp.listen	SGW-U PFCP listen address.
pfcp.allowed_sgwc[]	SGW-C control addresses allowed to use PFCP.
interfaces.user.<name>.ifname	Linux interface used by a named user-plane interface.
interfaces.user.<name>.listen	GTP-U local address for that named user-plane interface.
gtpu.s1u.bind	Named user-plane interface used for S1-U.
gtpu.s5u.bind	Named user-plane interface used for S5/S8-U.
qos.outer_marking.enabled	Enables outer IP DSCP marking.
qos.outer_marking.gtpu.enabled	Enables DSCP marking on forwarded GTP-U outer IPv4 headers.
qos.outer_marking.gtpu.dscp	GTP-U outer DSCP value, range 0-63. Default 0.
qos.outer_marking.pfcp.enabled	Enables DSCP marking on SGW-U PFCP sockets.
qos.outer_marking.pfcp.dscp	PFCP DSCP value, range 0-63. Default 40.
qos.qci_marking.enabled	Enables QCI-aware GTP-U outer DSCP marking for known bearer rules.
qos.qci_marking.override_default_gtpu	Uses QCI mapping instead of outer_marking.gtpu.dscp when bearer QCI metadata is available.
qos.qci_marking.default_gtpu_dscp	DSCP used when QCI marking is enabled but bearer QCI is missing or unmapped.
qos.qci_marking.unknown_teid_dscp	Reserved fallback DSCP setting for unknown TEID handling.
qos.qci_marking.trust_inner_dscp	Must be false; copying UE inner DSCP is not supported.
qos.qci_marking.qci_to_dscp	Operator QCI-to-DSCP map. QCI range 1-255, DSCP range 0-63. Defaults include QCI 1 to DSCP 46, QCI 5 to DSCP 40, QCI 9 to DSCP 0.
dataplane.driver_mode	XDP attach mode: xdp-generic, xdp-native, or xdp-offload.
dataplane.unknown_teid	Unknown TEID action: punt or drop.
dataplane.attach_on_start	Attach the eBPF dataplane during startup.
dataplane.cleanup_on_exit	Remove eBPF hooks during shutdown.
dataplane.map_max_entries	eBPF map capacity.
logging.level	Log level.
logging.file	Log file path.
api.listen	SGW-U HTTP API listen address.
metrics.listen	SGW-U metrics listen address.
shutdown.timeout_seconds	Graceful shutdown timeout.

Required SGW-U fields include sgwu.node_id, pfcp.listen, at least one pfcp.allowed_sgwc entry, gtpu.s1u.bind, and gtpu.s5u.bind.

S1-U and S5/S8-U listen addresses must use explicit IPv4 addresses, not 0.0.0.0.

Interfaces and Ports

Interface	Protocol	Default port
S11	GTPv2-C	UDP/2123
S5/S8-C	GTPv2-C	UDP/2123
Sxa	PFCP	UDP/8805
S1-U	GTP-U	UDP/2152
S5/S8-U	GTP-U	UDP/2152
SGW-C API	HTTP	TCP/8080
SGW-U API	HTTP	TCP/8081
SGW-C metrics	HTTP	TCP/9090
SGW-U metrics	HTTP	TCP/9091

Example Lab Configs

configs/interop/ contains lab templates for a two-node SGW-C/SGW-U deployment:

• configs/interop/sgw-c-lab.yaml
• configs/interop/sgw-u-lab.yaml

They set lab IP addresses, PFCP peer wiring, shared control-plane binding, and VM-friendly xdp-generic dataplane mode.