Aspi Siganporia
Aspi Siganporia is director of engineering at Google. From 1990-2006, he worked at various start-up and established networking companies in the Silicon Valley such as Netsys and Cisco Systems. Aspi received his BTech degree in electrical engineering from IIT Mumbai in 1982, and his MS degree in computer science from the University of Louisiana in 1986.
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Authored Publications
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BwE: Flexible, Hierarchical Bandwidth Allocation for WAN Distributed Computing
Björn Carlin
C. Stephen Gunn
Enrique Cauich Zermeno
Jing Ai
Mathieu Robin
Nikhil Kasinadhuni
Sushant Jain
ACM SIGCOMM 2015 (to appear)
Preview abstract
WAN bandwidth remains a constrained resource that is economically infeasible to substantially overprovision. Hence,it is important to allocate capacity according to service priority and based on the incremental value of additional allocation in particular bandwidth regions. For example, it may be highest priority for one service to receive 10Gb/s of bandwidth but upon reaching such an allocation, incremental priority may drop sharply favoring allocation to other services. Motivated by the observation that individual flows with fixed priority may not be the ideal basis for bandwidth allocation, we present the design and implementation of Bandwidth Enforcer (BwE), a global, hierarchical bandwidth allocation infrastructure. BwE supports: i) service-level bandwidth allocation following prioritized bandwidth functions where a service can represent an arbitrary collection of ows, ii) independent allocation and delegation policies according to user-defined hierarchy, all accounting for a global view of bandwidth and failure conditions, iii) multi-path forwarding common in traffic-engineered networks, and iv) a central administrative point to override (perhaps faulty) policy during exceptional conditions. BwE has delivered more service-efficient bandwidth utilization and simpler management in production for multiple years.
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BwE: Flexible, Hierarchical Bandwidth Allocation for WAN Distributed Computing
Sushant Jain
Nikhil Kasinadhuni
Enrique Cauich Zermeno
C. Stephen Gunn
Jing Ai
Björn Carlin
Mathieu Robin
Amin Vahdat
Sigcomm '15, Google Inc (2015)
Preview abstract
WAN bandwidth remains a constrained resource that is economically infeasible to substantially overprovision. Hence, it is important to allocate capacity according to service priority and based on the incremental value of additional allocation. For example, it may be the highest priority for one service to receive 10Gb/s of bandwidth but upon reaching such an allocation, incremental priority may drop sharply favoring allocation to other services. Motivated by the observation that individual flows with fixed priority may not be the ideal basis for bandwidth allocation, we present the design and implementation of Bandwidth Enforcer (BwE), a global, hierarchical bandwidth allocation infrastructure. BwE supports: i) service-level bandwidth allocation following prioritized bandwidth functions where a service can represent an arbitrary collection of flows, ii) independent allocation and delegation policies according to user-defined hierarchy, all accounting for a global view of bandwidth and failure conditions, iii) multi-path forwarding common in traffic-engineered networks, and iv) a central administrative point to override (perhaps faulty) policy during exceptional conditions. BwE has delivered more service-efficient bandwidth utilization and simpler management in production for multiple years.
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LatLong: Diagnosing Wide-Area Latency Changes for CDNs
Yaping Zhu
Benjamin Helsley
Jennifer Rexford
IEEE Transactions on Network and Service Management, 9 (2012) (to appear)
Preview abstract
Minimizing user-perceived latency is crucial for Content Distribution Networks (CDNs) hosting interactive services. Latency may increase for many reasons, such as interdomain routing changes and the CDN's own load-balancing policies. CDNs need greater visibility into the causes of latency increases, so they can adapt by directing traffic to different servers or paths. In this paper, we propose techniques for CDNs to diagnose large latency increases, based on passive measurements of performance, traffic, and routing. Separating the many causes from the effects is challenging. We propose a decision tree for classifying
latency changes, and determine how to distinguish traffic shifts from increases in latency for existing servers, routers, and paths. Another challenge is that network operators group related clients to reduce measurement and control overhead, but the clients in a region may use multiple servers and paths during a measurement interval. We propose metrics that quantify the latency contributions
across sets of servers and routers. Analyzing a month of data from Google's CDN, we find that nearly 1% of the
daily latency changes increase delay by more than 100 msec. More than 40% of these increases coincide with interdomain routing changes, and more than one-third involve a shift in traffic to different servers. This is the first work to diagnose latency problems in a large, operational CDN from purely passive measurements. Through case studies of individual events, we identify research challenges for measuring and managing wide-area latency for CDNs.
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