What causes "packet is older than packet group start" in livekit/livekit?

None needed — stale packets are intentionally excluded from the estimate.

packet is older than packet group start

Error message

packet is older than packet group start

What it means

A PacketGroup tracks packets starting from a minimum sequence number; a packet with a sequence number below that start is stale relative to the group and rejected with errOldPacket rather than being counted in bandwidth calculations.

Source

Thrown at pkg/sfu/bwe/sendsidebwe/packet_group.go:30

// See the License for the specific language governing permissions and
// limitations under the License.

package sendsidebwe

import (
	"errors"
	"time"

	"github.com/livekit/protocol/logger"
	"github.com/livekit/protocol/utils"
	"go.uber.org/zap/zapcore"
)

// -------------------------------------------------------------

var (
	errGroupFinalized = errors.New("packet group is finalized")
	errOldPacket      = errors.New("packet is older than packet group start")
)

// -------------------------------------------------------------

type PacketGroupConfig struct {
	MinPackets        int           `yaml:"min_packets,omitempty"`
	MaxWindowDuration time.Duration `yaml:"max_window_duration,omitempty"`
}

var (
	defaultPacketGroupConfig = PacketGroupConfig{
		MinPackets:        30,
		MaxWindowDuration: 500 * time.Millisecond,
	}
)

// -------------------------------------------------------------

View on GitHub (pinned to ee45c3f0b1)

Solutions

None needed — stale packets are intentionally excluded from the estimate.
If frequent, investigate packet reordering or feedback delay in the network path.
Upgrade LiveKit for group-rollover refinements in send-side BWE.
Monitor alongside 'packet group is finalized' logs to spot boundary churn.

Defensive patterns

Strategy: try-catch

Try / catch

if err := opg.Add(pi, sendDelta, recvDelta, isLost); err != nil {
  if errors.Is(err, errOldPacket) { return /* stale, skip */ }
  if errors.Is(err, errGroupFinalized) { /* start new group */ }
}

Prevention

Ignore errOldPacket — stale packets must not affect estimates.
Sequence packet feedback monotonically before feeding the detector.
Avoid replaying buffered deltas after group rollover.
Correlate with errGroupFinalized logs to detect boundary churn.

When it happens

Trigger: onPacketReceived delivering a transport-cc packet whose sequence number precedes the current group's minSequenceNumber — typically after group rollover or when processing buffered/delayed feedback.

Common situations: Reordered packet arrival across group boundaries; delayed send/recv delta reports being fed after a new group started; burst catch-up after a processing stall.

Related errors

AI-assisted analysis of livekit/livekit@ee45c3f0b1 (2026-09-02). Data as JSON: /api/errors/e15124736c71661a. Report an issue: GitHub.