Author: liangzhu

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Papers Publications

new conference paper “LDplayer: DNS Experimentation at Scale” at ACM IMC 2018

We have published a new paper LDplayer: DNS Experimentation at Scale by Liang Zhu and John Heidemann, in the ACM Internet Measurements Conference (IMC 2018) in Boston, Mass., USA.

Figure 14a: Evaluation of server memory with different TCP timeouts and minimal RTT (<1 ms). Trace: B-Root-17a. Protocol: TLS

From the abstract:

DNS has evolved over the last 20 years, improving in security and privacy and broadening the kinds of applications it supports. However, this evolution has been slowed by the large installed base and the wide range of implementations. The impact of changes is difficult to model due to complex interactions between DNS optimizations, caching, and distributed operation. We suggest that experimentation at scale is needed to evaluate changes and facilitate DNS evolution. This paper presents LDplayer, a configurable, general-purpose DNS experimental framework that enables DNS experiments to scale in several dimensions: many zones, multiple levels of DNS hierarchy, high query rates, and diverse query sources. LDplayer provides high fidelity experiments while meeting these requirements through its distributed DNS query replay system, methods to rebuild the relevant DNS hierarchy from traces, and efficient emulation of this hierarchy on minimal hardware. We show that a single DNS server can correctly emulate multiple independent levels of the DNS hierarchy while providing correct responses as if they were independent. We validate that our system can replay a DNS root traffic with tiny error (± 8 ms quartiles in query timing and ± 0.1% difference in query rate). We show that our system can replay queries at 87k queries/s while using only one CPU, more than twice of a normal DNS Root traffic rate. LDplayer’s trace replay has the unique ability to evaluate important design questions with confidence that we capture the interplay of caching, timeouts, and resource constraints. As an example, we demonstrate the memory requirements of a DNS root server with all traffic running over TCP and TLS, and identify performance discontinuities in latency as a function of client RTT.

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Publications Technical Report

new technical report “LDplayer: DNS Experimentation at Scale (abstract with poster)”

We released a new technical report “LDplayer: DNS Experimentation at Scale (abstract with poster)”, ISI-TR-721, available at https://www.isi.edu/publications/trpublic/pdfs/ISI-TR-721.pdf.

The poster abstract and poster (included as part of the technical report) appeared at the poster session at the SIGCOMM 2017 in August 2017 in Los Angeles, CA, USA.

From the abstract:

In the last 20 years the core of the Domain Name System (DNS) has improved in security and privacy, and DNS use broadened from name-to-address mapping to a critical roles in service discovery and anti-spam. However, protocol evolution and expansion of use has been slow because advances must consider a huge and diverse installed base. We suggest that experimentation at scale can fill this gap. To meet the need for experimentation at scale, this paper presents LDplayer, a configurable, general-purpose DNS testbed. LDplayer enables DNS experiments to scale in several dimensions: many zones, multiple levels of DNS hierarchy, high query rates, and diverse query sources. To meet these requirements while providing high fidelity experiments, LDplayer includes a distributed DNS query replay system and methods to rebuild the relevant DNS hierarchy from traces. We show that a single DNS server can correctly emulate multiple independent levels of the DNS hierarchy while providing correct responses as if they were independent. We show the importance of our system to evaluate pressing DNS design questions, using it to evaluate changes in DNSSEC key size.

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Papers Publications

new conference paper “Measuring the Latency and Pervasiveness of TLS Certificate Revocation” in PAM 2016

The paper “Measuring the Latency and Pervasiveness of TLS Certificate Revocation” will appear at Passive and Active Measurements Conference in March 2016 in Heraklion, Crete, Greece  (available at http://www.isi.edu/~liangzhu/papers/Zhu16a.pdf)

From the abstract:

Today, Transport-Layer Security (TLS) is the bedrock of Internet security for the web and web-derived applications. TLS depends on the X.509 Public Key Infrastructure (PKI) to authenticate endpoint
identity. An essential part of a PKI is the ability to quickly revoke certificates, for example, after a key compromise. Today the Online Certificate Status Protocol (OCSP) is the most common way to quickly distribute revocation information. However, prior and current concerns about OCSP latency and privacy raise questions about its use. We examine OCSP using passive network monitoring of live traffic at the Internet uplink of a large research university and verify the results using active scans. Our measurements show that the median latency of OCSP queries is quite good: only 20 ms today, much less than the 291 ms observed in 2012. This improvement is because content delivery networks (CDNs) serve most OCSP traffic today; our measurements show 94% of queries are served by CDNs. We also show that OCSP use is ubiquitous today: it is used by all popular web browsers, as well as important non-web applications such as MS-Windows code signing.

The work in the paper is by Liang Zhu (USC/ISI), Johanna Amann (ICSI) and John Heidemann (USC/ISI). The active probe dataset in this paper is available upon request.

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Software releases

Digit tool for T-DNS privacy updated to match current internet-draft

Digit is our DNS client side tool that can perform DNS queries via different protocols such as UDP, TCP, TLS. This tool is primarily designed to evaluate the client side latency of using DNS over TCP/TLS.

IANA has allocated port 853 to use TLS/DTLS for DNS temporarily in the most recent version of Internet draft “DNS over TLS: Initiation and Performance Considerations” (draft-ietf-dprive-dns-over-tls-01).

To track the current specification, we have updated Digit to do direct TLS on port 853 by default, with TCP. STARTTLS and other protocols as options for comparison.

These changes are available as Digit-1.4.1 at https://ant.isi.edu/software/tdns/index.html.

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Papers Publications

new conference paper “Connection-Oriented DNS to Improve Privacy and Security” in Oakland 2015

The paper “Connection-Oriented DNS to Improve Privacy and Security” will appear at the 36th IEEE Symposium on Security and Privacy in May 2015 in San Jose, CA, USA  (available at http://www.isi.edu/~liangzhu/papers/Zhu15b.pdf)

From the abstract:end_to_end_model_n_7

The Domain Name System (DNS) seems ideal for connectionless UDP, yet this choice results in challenges of eavesdropping that compromises privacy, source-address spoofing that simplifies denial-of-service (DoS) attacks on the server and third parties, injection attacks that exploit fragmentation, and reply-size limits that constrain key sizes and policy choices. We propose T-DNS to address these problems. It uses TCP to smoothly support large payloads and to mitigate spoofing and amplification for DoS. T-DNS uses transport-layer security (TLS) to provide privacy from users to their DNS resolvers and optionally to authoritative servers. TCP and TLS are hardly novel, and expectations about DNS suggest connections will balloon client latency and overwhelm server with state. Our contribution is to show that T-DNS significantly improves security and privacy: TCP prevents denial-of-service (DoS) amplification against others, reduces the effects of DoS on the server, and simplifies policy choices about key size. TLS protects against eavesdroppers to the recursive resolver. Our second contribution is to show that with careful implementation choices, these benefits come at only modest cost: end-to-end latency from TLS to the recursive resolver is only about 9% slower when UDP is used to the authoritative server, and 22% slower with TCP to the authoritative. With diverse traces we show that connection reuse can be frequent (60–95% for stub and recursive resolvers, although half that for authoritative servers), and after connection establishment, experiments show that TCP and TLS latency is equivalent to UDP. With conservative timeouts (20 s at authoritative servers and 60 s elsewhere) and estimated per-connection memory, we show that server memory requirements match current hardware: a large recursive resolver may have 24k active connections requiring about 3.6 GB additional RAM. Good performance requires key design and implementation decisions we identify: query pipelining, out-of-order responses, TCP fast-open and TLS connection resumption, and plausible timeouts.

The work in the paper is by Liang Zhu, Zi Hu and John Heidemann (USC/ISI), Duane Wessels and Allison Mankin (both of Verisign Labs), and Nikita Somaiya (USC/ISI).  Earlier versions of this paper were released as ISI-TR-688 and ISI-TR-693; this paper adds results and supercedes that work.

The data in this paper is available to researchers at no cost on request. Please see T-DNS-experiments-20140324 at dataset page.

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Papers Publications

new workshop paper “Measuring DANE TLSA Deployment” in TMA 2015

The paper “Measuring DANE TLSA Deployment” will appear at the Traffic Monitoring and Analysis Workshop in April 2015 in Barcelona, Spain (available at http://www.isi.edu/~liangzhu/papers/dane_tlsa.pdf).

From the abstract:

The DANE (DNS-based Authentication of Named Entities) framework uses DNSSEC to provide a source of trust, and with TLSA it can serve as a root of trust for TLS certificates. This serves to complement traditional certificate authentication methods, which is important given the risks inherent in trusting hundreds of organizations—risks already demonstrated with multiple compromises. The TLSA protocol was published in 2012, and this paper presents the first systematic study of its deployment. We studied TLSA usage, developing a tool that actively probes all signed zones in .com and .net for TLSA records. We find the TLSA use is early: in our latest measurement, of the 485k signed zones, we find only 997 TLSA names. We characterize how it is being used so far, and find that around 7–13% of TLSA records are invalid. We find 33% of TLSA responses are larger than 1500 Bytes and will very likely be fragmented.

The work in the paper is by Liang Zhu (USC/ISI), Duane Wessels and Allison Mankin (both of Verisign Labs), and John Heidemann (USC/ISI).

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Presentations

new talk “Measuring DANE TLSA Deployment” given at DNS-OARC

Liang Zhu gave the talk “Measuring DANE TLSA Deployment”, given at the Fall DNS-OARC meeting in Los Angeles, California on Oct 12, 2014.  Slides are available: http://www.isi.edu/~liangzhu/presentation/dns-oarc/dane_tlsa_survey.pdf

From the abstract:

The DANE (DNS-based Authentication of Named Entities) framework uses DNSSEC to provide a source of trust, and with TLSA it can serve as a root of trust for TLS certificates. This alternative to traditional certificate authorities is important given the risks inherent in trusting hundreds of organizations—risks already demonstrated with multiple compromises. The TLSA protocol was published in 2012, and this talk presents the first systematic study of its deployment. We studied TLSA usage, developing a tool that actively probes all signed zones in .com and .net for TLSA records. We find the TLSA use is early: in our latest measurement, of the 461k signed zones, we find only 701 TLSA names. We characterize how it is being used so far, and find that around 7–12% of TLSA records are invalid. We find 31% of TLSA responses are larger than 1500 Bytes and get IP fragmented.

The work in the talk is by Liang Zhu (USC/ISI), Duane Wessels and Allison Mankin (both of Verisign), and John Heidemann (USC/ISI).

Categories
Publications Technical Report

new technical report “T-DNS: Connection-Oriented DNS to Improve Privacy and Security (extended)”

We released a new technical report “T-DNS: Connection-Oriented DNS to Improve Privacy and Security (extended)”, ISI-TR-2014-693, available as http://www.isi.edu/~johnh/PAPERS/Zhu14b.pdf

From the abstract:resp_cdf_diff_key_all

DNS is the canonical protocol for connectionless UDP. Yet DNS today is challenged by eavesdropping that compromises privacy, source-address spoofing that results in denial-of-service (DoS) attacks on the server and third parties, injection attacks that exploit fragmentation, and size limitations that constrain policy and operational choices. We propose T-DNS to address these problems. It uses TCP to smoothly support large payloads and to mitigate spoofing and amplification for DoS. T-DNS uses transport-layer security (TLS) to provide privacy from users to their DNS resolvers and optionally to authoritative servers. Expectations about DNS suggest connections will balloon client latency and overwhelm server with state, but our evaluation shows costs are modest: end-to-end latency from TLS to the recursive resolver is only about 9% slower when UDP is used to the authoritative server, and 22% slower with TCP to the authoritative. With diverse traces we show that frequent connection reuse is possible (60–95% for stub and recursive resolvers, although half that for authoritative servers), and after connection establishment, we show TCP and TLS latency is equivalent to UDP. With conservative timeouts (20 s at authoritative servers and 60 s elsewhere) and conservative estimates of connection state memory requirements, we show that server memory requirements match current hardware: a large recursive resolver may have 24k active connections requiring about 3.6 GB additional RAM. We identify the key design and implementation decisions needed to minimize overhead: query pipelining, out-of-order responses, TLS connection resumption, and plausible timeouts.

This paper is a major revision of the prior technical report ISI-TR-2014-688. Since that work we have improved our understanding of the availability of TCP fast open and TLS resumption, and we have tightened our estimates on memory based on external reports (section 5.2). This additional information has allowed us to conduct additional experiments, improve our modeling, and provide a more accurate view of what is possible today; our estimates of latency and memory consumption are both lower than in our prior technical report as a result. We have also added additional information about packet size limitations (Figure 2), experiments evaluating DNSCrypt/DNSCurve (section 6.1), analysis of DTLS, and covered a broader range of RTTs in our experiments. We believe these additions strengthen our central claims: that connectionless DNS causes multiple problems and that T-DNS addresses those problems with modest increase in latency and memory suitable for current hardware.

Categories
Publications Technical Report

new technical report “T-DNS: Connection-Oriented DNS to Improve Privacy and Security”

We released a new technical report “T-DNS: Connection-Oriented DNS to Improve Privacy and Security”, ISI-TR-2014-688, available as http://www.isi.edu/~johnh/PAPERS/Zhu14a.pdf

 

From the abstract:sim_hit_server_median_all

This paper explores connection-oriented DNS to improve DNS security and privacy. DNS is the canonical example of a connectionless, single packet, request/response protocol, with UDP as its dominant transport. Yet DNS today is challenged by eavesdropping that compromises privacy, source-address spoofing that results in denial-of-service (DoS) attacks on the server and third parties, injection attacks that exploit fragmentation, and size limitations that constrain policy and operational choices. We propose t-DNS to address these problems: it combines TCP to smoothly support large payloads and mitigate spoofing and amplification for DoS. T-DNS uses transport-layer security (TLS) to provide privacy from users to their DNS resolvers and optionally to authoritative servers. Traditional wisdom is that connection setup will balloon latency for clients and overwhelm servers. These are myths—our model of end-to-end latency shows TLS to the recursive resolver is only about 21% slower, with UDP to the authoritative server. End-to-end latency is 90% slower with TLS to recursive and TCP to authoritative. Experiments behind these models show that after connection establishment, TCP and TLS latency is equivalent to UDP. Using diverse trace data we show that frequent connection reuse is possible (60–95% for stub and recursive resolvers, although half that for authoritative servers). With conservative timeouts (20 s at authoritative servers and 60 s elsewhere) we show that server memory requirements match current hardware: a large recursive resolver may have 25k active connections consuming about 9 GB of RAM. We identify the key design and implementation decisions needed to minimize overhead—query pipelining, out-of-order responses, TLS connection resumption, and plausible timeouts.