NTP and PTP Random Thoughts on Trade-offs and Scalability IETF 68 TICTOC BOF Karen O’Donoghue +1-540-653-1567

Objective As requested by the BOF organizers: Kickoff a discussion on the tradeoffs between NTP and PTP (IEEE 1588), in particular as related to scalability Thought provoking slides? As revised by the speaker: Identify some basic metrics for scalability Propose a possible way ahead Rationale for revision: May be a bit premature to discuss specific NTP/PTP tradeoffs (suffice it to say they exist…) 15 March 2007

Characteristics of Scalability What are scalability requirements? Number of clients/slaves supported Number of servers/masters available Number of network or infrastructure devices Clock (tod and/or freq) aware (e.g. transparent clocks) Non-clock (tod and/or freq) aware Mixture Number and types of networks traversed Logical and Geographic distance Available bandwidth If a potential WG is limited to infrastructure networks, how can the requirements be narrowed/clarified? 15 March 2007

Impacts to Scalability What impacts scalability? Client/server approach versus Master/slave approach Server/master complexity Client/slave complexity Hardware requirement Network design Communications model Unicast versus Multicast Protocol Operations Modes of operation (NTP) Types of devices (PTP) Algorithm complexity Edge cases Master/server selection and redundancy 15 March 2007

Clock Standardization Activities At a Glance IETF (NTP) Pros Scalable and robust Subnet technology independent Represents the generic computing equipment market Wide scale deployment and years of experience Cons Does not address high end synchronization requirements in an open standard manner IEEE 1588 (PTP) Pros Designed for high precision applications Industrial automation and telecom industries have real time requirements Cons Lacks the robustness and deployment experience of NTP Currently represents a niche market relative to generic computing equipment and enterprise deployments IEEE 802.1AS Pros Hardware time stamp capability available in every Ethernet NIC (mass market availability) Cons Immature at this point Targets consumer market (may not be suitable for enterprise or telecom infrastructures) Note: Each of these solutions has some overlap and addresses some unique aspects of the problem (not an apples to apples comparison). 15 March 2007

Given that: There are various solutions addressing parts (but not all) of the problem space There is a significant investment in this problem space represented by NTP and PTP There is an expectation that both NTP and PTP will be encountered in the future Perhaps: There are aspects of both that can be identified and leveraged for a next generation solution At the very least, an interface between the two should be considered 15 March 2007

Possible TICTOC Way Ahead Clarify requirements Both time and frequency Define a modular architecture Analyze/Decompose existing solutions in terms of this architecture Identify existing components that can be leveraged in the new modular architecture Identify any enhancements required to these existing components Define new components needed to complete the architecture Don’t reinvent the wheel 15 March 2007

Discussion? 15 March 2007