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feat(router): add deadband for route switching #114

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Merged
encodeous merged 1 commit into from
May 17, 2026
Merged

feat(router): add deadband for route switching #114

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6 changes: 3 additions & 3 deletions core/router_algo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -556,7 +556,7 @@ func ComputeRoutes(s *state.RouterState, r Router) {
continue
}
}
if ShouldSwitch(oldRoute, newRoute) {
if ShouldSwitch(oldRoute, newRoute, s.RouterTunables) {
newTable[prefix] = newRoute
}
}
Expand Down Expand Up @@ -671,11 +671,11 @@ func SolveStarvation(router *state.RouterState, r Router) {
// requests are expected to actually reach the source.)
}

func ShouldSwitch(curRoute state.SelRoute, newRoute state.SelRoute) bool {
func ShouldSwitch(curRoute state.SelRoute, newRoute state.SelRoute, tunable *state.RouterTunables) bool {
// TODO: Investigate stable routing heuristics
curMetric := float64(curRoute.Metric)
newMetric := float64(newRoute.Metric)
if newMetric > curMetric {
if newMetric*tunable.LinkSwitchDeadband > curMetric {
return false
}
return true
Expand Down
12 changes: 6 additions & 6 deletions core/router_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -157,7 +157,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
// / | FD(A) = 1
// S |1
// \ | D(B) = 2
// 2 \| FD(B) = 2
// 3 \| FD(B) = 2
// B

h := &RouterHarness{}
Expand All @@ -172,7 +172,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
}

AS := AddLink(rs, NewMockEndpoint("A", 1))
_ = AddLink(rs, NewMockEndpoint("B", 2))
_ = AddLink(rs, NewMockEndpoint("B", 3))

// A's advertised routes
h.NeighUpdate(rs, "A", "S", nodeToPrefix("S"), 0, 1)
Expand All @@ -182,7 +182,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
// B's advertised routes
h.NeighUpdate(rs, "B", "B", nodeToPrefix("B"), 0, 0)
h.NeighUpdate(rs, "B", "A", nodeToPrefix("A"), 0, 1)
h.NeighUpdate(rs, "B", "S", nodeToPrefix("S"), 0, 2)
h.NeighUpdate(rs, "B", "S", nodeToPrefix("S"), 0, 3)

ComputeRoutes(rs, h)
a := h.GetActions()
Expand All @@ -193,7 +193,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
)
assert.Equal(t, `10.0.0.1/32 via (nh: A, router: A, prefix: 10.0.0.1/32, seqno: 0, metric: 1)
10.0.0.19/32 via (nh: S, router: S, prefix: 10.0.0.19/32, seqno: 0, metric: 0)
10.0.0.2/32 via (nh: B, router: B, prefix: 10.0.0.2/32, seqno: 0, metric: 2)`, rs.StringRoutes())
10.0.0.2/32 via (nh: A, router: B, prefix: 10.0.0.2/32, seqno: 0, metric: 2)`, rs.StringRoutes())

// check feasibility distances
assert.Equal(t, state.FD{Seqno: 0, Metric: 1}, rs.Sources[state.Source{NodeId: "A", Prefix: nodeToPrefix("A")}])
Expand All @@ -206,7 +206,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
// | FD(A) = 1
// S |1
// \ | D(B) = 2
// 2 \| FD(B) = 2
// 3 \| FD(B) = 2
// B

RemoveLink(rs, AS)
Expand Down Expand Up @@ -244,7 +244,7 @@ func TestRouterNet2S_SolveStarvation(t *testing.T) {
},
FD: state.FD{
Seqno: 1,
Metric: 3,
Metric: 4,
},
}
a.AssertContains(t, BroadcastUpdateRoute(pr))
Expand Down
14 changes: 8 additions & 6 deletions state/tunables.go
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Expand Up @@ -23,9 +23,10 @@ type RouterTunables struct {
// MinimumConfidenceWindow is the minimum number of samples before we lower the ping
MinimumConfidenceWindow int

GcDelay time.Duration
LinkDeadThreshold time.Duration
RouteExpiryTime time.Duration
GcDelay time.Duration
LinkDeadThreshold time.Duration
RouteExpiryTime time.Duration
LinkSwitchDeadband float64 // We will switch to a new feasible route if: metric(new) * LinkSwitchDeadband <= metric(old)

// client configuration
ClientKeepaliveInterval time.Duration
Expand Down Expand Up @@ -75,9 +76,10 @@ func DefaultRouterTunables() RouterTunables {
OutlierPercentage: 0.05,
MinimumConfidenceWindow: int(time.Second * 15 / probeDelay),

GcDelay: time.Millisecond * 1000,
LinkDeadThreshold: 5 * probeDelay,
RouteExpiryTime: 5 * routeUpdateDelay,
GcDelay: time.Millisecond * 1000,
LinkDeadThreshold: 5 * probeDelay,
RouteExpiryTime: 5 * routeUpdateDelay,
LinkSwitchDeadband: 1.1,

ClientKeepaliveInterval: 3 * probeDelay,
ClientDeadThreshold: 6 * probeDelay, // 2 * ClientKeepaliveInterval
Expand Down
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