Notes From Usenix Nsdi Eighteen Kickoff Twenty-Four Lx Minutes Menses
I have got been attending USENIX NSDI, 1 of the premier conferences on networking, at Seattle, WA. Here are simply about notes from the outset day, Monday, Apr 9.
The best newspaper is awarded to "NetChain: Scale-Free Sub-RTT Coordination" by Xin Jin, Johns Hopkins University; Xiaozhou Li, Barefoot Networks; Haoyu Zhang, Princeton University; Nate Foster, Cornell University; Jeongkeun Lee, Barefoot Networks; Robert Soulé, Università della Svizzera italiana; Changhoon Kim, Barefoot Networks; Ion Stoica, UC Berkeley.
The community respect (best newspaper whose code too dataset made publicly available) went to "Stateless Datacenter Load-balancing amongst Beamer" past times Vladimir Olteanu, Alexandru Agache, Andrei Voinescu, too Costin Raiciu, University Politehnica of Bucharest.
NSDI makes all papers available publicly. So if whatever of the papers hither involvement you, you tin download too read the paper.
Congestion command today done via end-to-end protocols. The switches are dumb. What if they were smarter? That would provide benefits for the terminate host too fairness, etc.
But, smart switches are challenging to realize for high-speed networks. In high-speed networks, it is difficult to
The operate implements imitation fair queuing (fair queueing without per menstruation queues) inwards high-speed switches. The approach is based on approximate fair queueing: simulate a chip past times chip circular robin scheme amongst cardinal approximations
The approximate menstruation counters are stored using a variation of count-min sketch. The results exhibit the approximate fair queueing is achieved via 12-14 queues. Evaluation also shows that approximate fair queuing leads to 4-8x improvement inwards menstruation completion times.
This operate received the best newspaper award. And it is also on the distributed coordination expanse I am interested in, thence I have got a relatively long coverage of this work.
Conventional wisdom says coordination is expensive. Netchain aims to provide lighting fast coordination enabled past times programmable switches. Some applications of the coordination service tin endure configuration management, grouping membership, locking, barrier synchronization.
Right at 1 time these are done over a coordination service running Paxos, which is frequently implemented over a strongly-consistent, fault-tolerant key-value store. Can nosotros practice amend inwards price of latency too throughput?
The chance for using in-network coordination is that distributed coordination is communication-heavy rather than computation-heavy. The thought is to run coordination inwards the switches using consensus. The pattern goals are to accomplish high-throughput too potent consistency.
How practice they build a strongly consistent fault-tolerant in-network (which way inwards the switches) keyvalue store? They utilization the chain replication protocol. That is, at that topographic point is a master copy configurator managing the chain configuration too the storage nodes on the chain that replicate the key-values.
The in-network (that is, on the switch) key-value storage builds on the SOSP 17 newspaper titled "NetCache: Balancing Key-Value Stores amongst Fast In-Network Caching" which leverages register arrays inwards the switches.
There is a work of possible out-of-order delivery betwixt the consecutive switches inwards the chain, which tin Pb to inconsistency. The presentation says they solve that amongst serialization amongst sequence lay out too dropping the out of lodge packet. The onus is on the customer to retry when its asking doesn't acquire a reply inwards time.
Of course of teaching the complicated component hither is for treatment a switch failure. Chain replication technique for recovery is adapted, thence that the master copy configurator (which is Paxos maintained) tin reconfigure the switch past times removing the crashed node. But too thence to proceed the fault-tolerance, subsequently a novel node needs to endure added. The newspaper says the master copy outset copies the state to the newly added 1 too and thence add together that to the chain. Of course, at that topographic point is a catching-up work of the newly added switch if the previous node proceed getting too inserting novel items. There needs to endure simply about blocking to coordinate it, in all probability via 2-phase commit. I apace scanned the paper, too didn't run into this discussed.
The newspaper has a TLA+ specification in the extended arxiv version. I checked the TLA+ model, too it assumes copying state to the novel switch is done atomically, which seems to endure an over-simplification of what needs to endure implemented inwards reality.
The operate is evaluated over 4 barefoot tofino switches too 4 commodity servers. I retrieve the presenter said that upto 100K key-value pairs could endure stored on 8Mb storage available on the switches. Compared to Zookeeper, the solution was able to render 3 orders of magnitude improvement inwards throughput too 1 lodge of magnitude improvement inwards read latency too 2 lodge of magnitude inwards write latency.
The presented concluded amongst asking what form of novel applications could endure enabled past times faster coordination service available at the datacenters. I am even thence unclear what subRTT way inwards the title, but I volition read the newspaper too write a longer review later.
Neha presented this paper, too pulled it off without using the give-and-take blockchain fifty-fifty once.
Verification provided past times distributed ledgers should non hateful everything is inwards the open. The companies require some privacy to proceed simply about occupation concern strategies too positions secret. On the other likewise much secrets is also a bad thing, at that topographic point needs to endure some auditability to foreclose bad actors.
zkLedger provides practical privacy too consummate auditing.
A big challenge hither is that a bad utilization instrumentalist banking corporation could omit transactions. zkledger jointly addresses the privacy too auditability requirements past times keeping an entry for every banking corporation inwards every transaction. To shroud values, zkLedger uses Pedersen commitments. The cardinal insight is that the auditor audits every transaction. zkLedger also uses an interactive map/reduce prototype over the ledger amongst non-interactive zero-knowledge proofs (NIZKs) to compute measurements that become beyond sums.
The abstract of the newspaper provides a skillful summary, thence hither it is:
Banks create digital property transactions that are visible alone to the organizations political party to the transaction, but are publicly verifiable. An auditor sends queries to banks, for illustration "What is the outstanding amount of a sure as shooting digital property on your remainder sheet?" too gets a response too cryptographic assurance that the response is correct. zkLedger has ii of import benefits over previous work. First, zkLedger provides fast, rich auditing amongst a novel proof scheme using Schnorr-type non-interactive zero-knowledge proofs. Unlike zk-SNARKs, our techniques practice non require trusted setup too alone rely on widely-used cryptographic assumptions. Second, zkLedger provides completeness; it uses a columnar ledger structure thence that banks cannot shroud transactions from the auditor, too participants tin utilization rolling caches to hit too verify answers quickly. We implement a distributed version of zkLedger that tin hit provably right answers to auditor queries on a ledger amongst a hundred K transactions inwards less than 10 milliseconds.
This operate aims to render accurate timestamping equally a primitive (with 10 nanosec accuracy) inwards datacenters at scale. Tightly-synchronized clocks have got applications inwards distributed systems specially for distributed databases, such equally spanner too cockroachdb.
The scheme they develop, Huygens, convey NIC timestamps (which is supported past times most electrical current generation NICs), too doesn't require specialized switches similar PTP. Other than the NIC timestamping support, Huygens is software based.
Huygens leverages iii cardinal ideas. First, coded probes are used for identifying too rejecting impure probe information which endure queuing delays. To reveal this, Huygens shipping 2 consecutive probe packets amongst known gap: 10microsecond (NIC timestamping) too checks the gap betwixt them on the receiving end. Only the probes amongst the original 10 microsecond gap are accepted equally pure, since they most probable have got experienced null queueing delays. Since the queues are changing fast, it is really unlikely both of the consecutive packets were dependent champaign to same nonzero queueing delay.
Second, Huygens processes the purified information amongst Support Vector Machines, a widely-used too powerful classifier, to accurately approximate one-way propagation times. (Huygens assume delay betwixt ii servers are symmetric.)
Finally, to reveal too right synchronization errors fifty-fifty further, Huygens exploits the network outcome that a grouping of pair-wise synchronized clocks must endure transitively synchronized.
One of the questions asked was most the high probing charge per unit of measurement employed past times this work. Another inquiry was most if this could endure extended to WAN? The presenter mentioned 10 microsecond accuracy inwards a WAN experiment, but I wonder if it is due to Google datacenters having somebody too high-speed links.
One really interesting inquiry was if this could endure used for measuring the temperature inwards datacenters? This is a non bad question, non a crazy one. High temperature way local clock starts to run slower, too at that topographic point is a predictable linear relationship. So if you lot have got tightly synchronized clocks, you lot tin stair out the drift from ideal too infer temperature increase/decrease.
I volition read too summarize this newspaper later, since I am interested inwards mechanisms too applications of clock synchronization inwards distributed systems. After our operate on hybrid logical clocks (HLC), nosotros had built a distributed monitoring system, Retroscope, using HLC.
I had provided a summary of this operate before inwards my blog. Please run into that.
The papers presented were:
The papers presented were:
The afternoon too especially tardily afternoon isn't actually non bad for listening to conference talks. To follow talks 1 needs to expend a lot of mental effort, because the deliveries are done really quickly. Moreover the context changes drastically from speak to talk, too that is also depleting attention.
I wonder, if at to the lowest degree the tardily afternoons are amend spent amongst panels, or to a greater extent than lively too less concentration-demanding activities.
I have got heard of this mass on these topics "When: The Scientific Secrets of Perfect Timing" past times Daniel Pink. I conception to banking corporation check that book.
Pre-session announcements
NSDI has twoscore papers accepted out of 255 papers. There was a refer of k reviews done for the conference. That is a lot of reviews past times really highly qualified people. It is a shame those reviews are non shared openly, those reviews could endure actually useful for the community to larn from, too providing them may also expose if at that topographic point were whatever sub-par reviews. There is a motility for opened upwards review process, too I hope it catches on at a wider scale.The best newspaper is awarded to "NetChain: Scale-Free Sub-RTT Coordination" by Xin Jin, Johns Hopkins University; Xiaozhou Li, Barefoot Networks; Haoyu Zhang, Princeton University; Nate Foster, Cornell University; Jeongkeun Lee, Barefoot Networks; Robert Soulé, Università della Svizzera italiana; Changhoon Kim, Barefoot Networks; Ion Stoica, UC Berkeley.
The community respect (best newspaper whose code too dataset made publicly available) went to "Stateless Datacenter Load-balancing amongst Beamer" past times Vladimir Olteanu, Alexandru Agache, Andrei Voinescu, too Costin Raiciu, University Politehnica of Bucharest.
NSDI makes all papers available publicly. So if whatever of the papers hither involvement you, you tin download too read the paper.
First session
The outset session was on novel hardware. The master copy theme hither was to run into how nosotros tin acquire the functioning hardware solutions offering amongst the programmability of software solutions. I render curt summaries of the presentations of ii papers. The session also included ii other papers titled "PASTE: A Network Programming Interface for Non-Volatile Main Memory" too "Azure Accelerated Networking: SmartNICs inwards the Public Cloud Microsoft".Approximating fair queueing on reconfigurable switches
The newspaper is past times Naveen Kr. Sharma too Ming Liu, University of Washington; Kishore Atreya, Cavium; Arvind Krishnamurthy, University of Washington.Congestion command today done via end-to-end protocols. The switches are dumb. What if they were smarter? That would provide benefits for the terminate host too fairness, etc.
But, smart switches are challenging to realize for high-speed networks. In high-speed networks, it is difficult to
- maintain a sorted bundle buffer
- store per-flow counters
- access too modify electrical current circular number.
The operate implements imitation fair queuing (fair queueing without per menstruation queues) inwards high-speed switches. The approach is based on approximate fair queueing: simulate a chip past times chip circular robin scheme amongst cardinal approximations
The approximate menstruation counters are stored using a variation of count-min sketch. The results exhibit the approximate fair queueing is achieved via 12-14 queues. Evaluation also shows that approximate fair queuing leads to 4-8x improvement inwards menstruation completion times.
NetChain: Scale-Free Sub-RTT Coordination
The newspaper is past times Xin Jin, Johns Hopkins University; Xiaozhou Li, Barefoot Networks; Haoyu Zhang, Princeton University; Nate Foster, Cornell University; Jeongkeun Lee, Barefoot Networks; Robert Soulé, Università della Svizzera italiana; Changhoon Kim, Barefoot Networks; Ion Stoica, UC Berkeley.This operate received the best newspaper award. And it is also on the distributed coordination expanse I am interested in, thence I have got a relatively long coverage of this work.
Conventional wisdom says coordination is expensive. Netchain aims to provide lighting fast coordination enabled past times programmable switches. Some applications of the coordination service tin endure configuration management, grouping membership, locking, barrier synchronization.
Right at 1 time these are done over a coordination service running Paxos, which is frequently implemented over a strongly-consistent, fault-tolerant key-value store. Can nosotros practice amend inwards price of latency too throughput?
The chance for using in-network coordination is that distributed coordination is communication-heavy rather than computation-heavy. The thought is to run coordination inwards the switches using consensus. The pattern goals are to accomplish high-throughput too potent consistency.
How practice they build a strongly consistent fault-tolerant in-network (which way inwards the switches) keyvalue store? They utilization the chain replication protocol. That is, at that topographic point is a master copy configurator managing the chain configuration too the storage nodes on the chain that replicate the key-values.
The in-network (that is, on the switch) key-value storage builds on the SOSP 17 newspaper titled "NetCache: Balancing Key-Value Stores amongst Fast In-Network Caching" which leverages register arrays inwards the switches.
There is a work of possible out-of-order delivery betwixt the consecutive switches inwards the chain, which tin Pb to inconsistency. The presentation says they solve that amongst serialization amongst sequence lay out too dropping the out of lodge packet. The onus is on the customer to retry when its asking doesn't acquire a reply inwards time.
Of course of teaching the complicated component hither is for treatment a switch failure. Chain replication technique for recovery is adapted, thence that the master copy configurator (which is Paxos maintained) tin reconfigure the switch past times removing the crashed node. But too thence to proceed the fault-tolerance, subsequently a novel node needs to endure added. The newspaper says the master copy outset copies the state to the newly added 1 too and thence add together that to the chain. Of course, at that topographic point is a catching-up work of the newly added switch if the previous node proceed getting too inserting novel items. There needs to endure simply about blocking to coordinate it, in all probability via 2-phase commit. I apace scanned the paper, too didn't run into this discussed.
The newspaper has a TLA+ specification in the extended arxiv version. I checked the TLA+ model, too it assumes copying state to the novel switch is done atomically, which seems to endure an over-simplification of what needs to endure implemented inwards reality.
The operate is evaluated over 4 barefoot tofino switches too 4 commodity servers. I retrieve the presenter said that upto 100K key-value pairs could endure stored on 8Mb storage available on the switches. Compared to Zookeeper, the solution was able to render 3 orders of magnitude improvement inwards throughput too 1 lodge of magnitude improvement inwards read latency too 2 lodge of magnitude inwards write latency.
The presented concluded amongst asking what form of novel applications could endure enabled past times faster coordination service available at the datacenters. I am even thence unclear what subRTT way inwards the title, but I volition read the newspaper too write a longer review later.
Second session
The instant session was on distributed systems, my favorite topic. I have got brief summaries of the iii papers presented inwards this session.zkLedger: Privacy-Preserving Auditing for Distributed Ledgers
This newspaper is past times Neha Narula, MIT Media Lab; Willy Vasquez, University of Texas at Austin; Madars Virza, MIT Media Lab.Neha presented this paper, too pulled it off without using the give-and-take blockchain fifty-fifty once.
Verification provided past times distributed ledgers should non hateful everything is inwards the open. The companies require some privacy to proceed simply about occupation concern strategies too positions secret. On the other likewise much secrets is also a bad thing, at that topographic point needs to endure some auditability to foreclose bad actors.
zkLedger provides practical privacy too consummate auditing.
A big challenge hither is that a bad utilization instrumentalist banking corporation could omit transactions. zkledger jointly addresses the privacy too auditability requirements past times keeping an entry for every banking corporation inwards every transaction. To shroud values, zkLedger uses Pedersen commitments. The cardinal insight is that the auditor audits every transaction. zkLedger also uses an interactive map/reduce prototype over the ledger amongst non-interactive zero-knowledge proofs (NIZKs) to compute measurements that become beyond sums.
The abstract of the newspaper provides a skillful summary, thence hither it is:
Banks create digital property transactions that are visible alone to the organizations political party to the transaction, but are publicly verifiable. An auditor sends queries to banks, for illustration "What is the outstanding amount of a sure as shooting digital property on your remainder sheet?" too gets a response too cryptographic assurance that the response is correct. zkLedger has ii of import benefits over previous work. First, zkLedger provides fast, rich auditing amongst a novel proof scheme using Schnorr-type non-interactive zero-knowledge proofs. Unlike zk-SNARKs, our techniques practice non require trusted setup too alone rely on widely-used cryptographic assumptions. Second, zkLedger provides completeness; it uses a columnar ledger structure thence that banks cannot shroud transactions from the auditor, too participants tin utilization rolling caches to hit too verify answers quickly. We implement a distributed version of zkLedger that tin hit provably right answers to auditor queries on a ledger amongst a hundred K transactions inwards less than 10 milliseconds.
Exploiting a Natural Network Effect for Scalable, Fine-grained Clock Synchronization
This newspaper is past times Yilong Geng, Shiyu Liu, too Zi Yin, Stanford University; Ashish Naik, Google Inc.; Balaji Prabhakar too Mendel Rosenblum, Stanford University; Amin Vahdat, Google Inc.This operate aims to render accurate timestamping equally a primitive (with 10 nanosec accuracy) inwards datacenters at scale. Tightly-synchronized clocks have got applications inwards distributed systems specially for distributed databases, such equally spanner too cockroachdb.
The scheme they develop, Huygens, convey NIC timestamps (which is supported past times most electrical current generation NICs), too doesn't require specialized switches similar PTP. Other than the NIC timestamping support, Huygens is software based.
Huygens leverages iii cardinal ideas. First, coded probes are used for identifying too rejecting impure probe information which endure queuing delays. To reveal this, Huygens shipping 2 consecutive probe packets amongst known gap: 10microsecond (NIC timestamping) too checks the gap betwixt them on the receiving end. Only the probes amongst the original 10 microsecond gap are accepted equally pure, since they most probable have got experienced null queueing delays. Since the queues are changing fast, it is really unlikely both of the consecutive packets were dependent champaign to same nonzero queueing delay.
Second, Huygens processes the purified information amongst Support Vector Machines, a widely-used too powerful classifier, to accurately approximate one-way propagation times. (Huygens assume delay betwixt ii servers are symmetric.)
Finally, to reveal too right synchronization errors fifty-fifty further, Huygens exploits the network outcome that a grouping of pair-wise synchronized clocks must endure transitively synchronized.
One of the questions asked was most the high probing charge per unit of measurement employed past times this work. Another inquiry was most if this could endure extended to WAN? The presenter mentioned 10 microsecond accuracy inwards a WAN experiment, but I wonder if it is due to Google datacenters having somebody too high-speed links.
One really interesting inquiry was if this could endure used for measuring the temperature inwards datacenters? This is a non bad question, non a crazy one. High temperature way local clock starts to run slower, too at that topographic point is a predictable linear relationship. So if you lot have got tightly synchronized clocks, you lot tin stair out the drift from ideal too infer temperature increase/decrease.
I volition read too summarize this newspaper later, since I am interested inwards mechanisms too applications of clock synchronization inwards distributed systems. After our operate on hybrid logical clocks (HLC), nosotros had built a distributed monitoring system, Retroscope, using HLC.
SnailTrail: Generalizing Critical Paths for Online Analysis of Distributed Dataflows
This newspaper is past times Moritz Hoffmann, Andrea Lattuada, John Liagouris, Vasiliki Kalavri, Desislava Dimitrova, Sebastian Wicki, Zaheer Chothia, too Timothy Roscoe, ETH Zurich.I had provided a summary of this operate before inwards my blog. Please run into that.
Third session
The 3rd department was on traffic management. I am non actually a networking guy, but I listened to these to acquire simply about to a greater extent than agreement on what is going on inwards this domain.The papers presented were:
- "Balancing on the Edge: Transport Affinity without Network State",
- "Stateless Datacenter Load-balancing amongst Beamer",
- "Larry: Practical Network Reconfigurability inwards the Data Center", and
- "Semi-Oblivious Traffic Engineering: The Road Not Taken"
Fourth session
The 4th session was on network component virtualization too hardware.The papers presented were:
- Metron: NFV Service Chains at the True Speed of the Underlying Hardware
- G-NET: Effective GPU Sharing inwards NFV Systems
- SafeBricks: Shielding Network Functions inwards the Cloud
MAD questions
Really, you lot read this far into this long post, too even thence await me to write simply about MAD questions? Ok, hither is simply one, thence that my hope is non broken.The afternoon too especially tardily afternoon isn't actually non bad for listening to conference talks. To follow talks 1 needs to expend a lot of mental effort, because the deliveries are done really quickly. Moreover the context changes drastically from speak to talk, too that is also depleting attention.
I wonder, if at to the lowest degree the tardily afternoons are amend spent amongst panels, or to a greater extent than lively too less concentration-demanding activities.
I have got heard of this mass on these topics "When: The Scientific Secrets of Perfect Timing" past times Daniel Pink. I conception to banking corporation check that book.
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