Two-Tier Resource Management Designed after the Internet’s two-tier routing hierarchy Separate packet forwarding from admission and resource allocation control Resource allocation adjustments can be made on much larger time scales Bandwidth Broker (BB) acts as resource manager for each domain Neighboring BBs communicate to allocate resources for each aggregate traffic class crossing domain borders according to relatively stable, long-lived SLAs between domains BB instructs its border (edge) routers to do aggregate shaping/policing End-to-end QoS is concatenation of QoS across originating, transit and receiving domains

Inter-Domain Protocol BB informs its egress border router (ER) to shape traffic according to SLA with neighbor domain When ER detects an increase in traffic volume to neighbor domain, it notifies its BB specifying address of neighbor ingress router (IR) BB contacts the neighbor BB to increase its allocation Neighbor BB asks its IR if there are sufficient internal resources IR uses its own intra-domain resource allocation protocol If enough resources, IR notifies its BB and adjusts its policer parameters Reply sent back to requesting BB, which informs its IR to update its shaper parameters

Resource Allocation Requests If current rate r from ER exceeds w * L (w <= 1), ER asks for increase BB asks for I * r (I > 1) I * r > L ==> I * w * L > L ==> I * w > 1 Lower w means larger spikes in traffic can be absorbed and longer delays in re-negotiation can be tolerated Higher I reduces the frequency of increase requests If r <= l * L (l < 1), ER asks for decrease BB keeps a hysteresis counter H, decremented by one each time ER asks for decrease When H = 0, BB sends decrease request of D * L (D <= 1) to neighbor BB Decreases happen only when traffic is consistently lower than the allocation D close to 1 means gradual decreases

Estimation Process Estimate r over a measurement window T If a newly computed average load over S < T is larger than r, set r to this value At end of T, set r to highest average load for any S period Decreasing S makes process more sensitive to bursts Increasing T increases the amount of history remembered

Intra-Domain Resource Allocation At source domain, source host sends RSVP PATH message toward flow’s receiver host First-hop router intercepts PATH message and informs BB of source host BB checks if enough resources on border link to downstream domain If OK, BB informs IR to send PATH message and ER replies with RESV message to reserve local resources Source’s traffic profile is advertised out of band at application level If OK, BB informs IR to send PATH message to receiver Receiver sends RESV to allocate local resources

Allocation in Transit Domains Each IR measures amount of traffic toward each ER Use RSVP to allocate resources for each IR-ER pair O(N^2) state, where N is number of edge routers Given each border router participates in BGP, it knows the ER that corresponds to a particular destination Based on rate to each ER, IR sends PATH message and ER responds with RESV When BB sends increase request to IR, how should this increase distributed among all ER’s? Assume newly admitted traffic will follow same distribution as current traffic, IR can send PATH messages with increase requests in same proportion ER responds with RESV to allocate local resources If assumption not true, notify BB