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object-src 'none'; report-uri /w/api.php?action=cspreport&format=json; report-to csp-report-to-endpoint last-modified: Sun, 21 Jun 2026 21:50:51 GMT content-type: text/html; charset=UTF-8 age: 71195 accept-ranges: bytes x-cache: cp2047 hit, cp2047 hit/3 x-cache-status: hit-front server-timing: cache;desc="hit-front", host;desc="cp2047" strict-transport-security: max-age=106384710; includeSubDomains; preload report-to: { "group": "wm_nel", "max_age": 604800, "endpoints": [{ "url": "https://intake-logging.wikimedia.org/v1/events?stream=w3c.reportingapi.network_error&schema_uri=/w3c/reportingapi/network_error/1.0.0" }] } nel: { "report_to": "wm_nel", "max_age": 604800, "failure_fraction": 0.05, "success_fraction": 0.0} set-cookie: WMF-Last-Access=03-Jul-2026;Path=/;HttpOnly;secure;Expires=Tue, 04 Aug 2026 12:00:00 GMT set-cookie: WMF-Last-Access-Global=03-Jul-2026;Path=/;Domain=.wikipedia.org;HttpOnly;secure;Expires=Tue, 04 Aug 2026 12:00:00 GMT set-cookie: WMF-DP=80e;Path=/;HttpOnly;secure;Expires=Sat, 04 Jul 2026 00:00:00 GMT x-client-ip: 75.28.18.94 cache-control: private, s-maxage=0, max-age=0, must-revalidate, no-transform vary: Accept-Encoding,X-Subdomain,Cookie,Authorization,User-Agent set-cookie: GeoIP=US:TX:McKinney:33.20:-96.62:v4; 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It is a common term in IP network monitoring , and differs from round-trip time (RTT) in that only the path in one direction, from source to destination, is measured. Measurement [ edit ] The ping utility measures the RTT, that is, the time to go and come back to a host. Half the RTT is often used as an approximation of OWD but this assumes that the forward and back paths are the same in terms of congestion, number of hops, or quality of service (QoS). This is not always a good assumption. To avoid such problems, the OWD may be measured directly. Direct [ edit ] OWDs may be measured between two points A and B of an IP network through the use of synchronized clocks; A records a timestamp on the packet and sends it to B , which notes the receiving time and calculates the OWD as their difference. The transmitted packets need to be identified at the source and destination in order to avoid packet loss or packet reordering. However, this method suffers from several limitations, such as requiring intensive cooperation between both parties, and the accuracy of the measured delay is subject to the synchronization precision. The Minimum-Pairs Protocol is an example by which several cooperating entities, A , B , and C , could measure OWDs between one of them and a fourth less cooperative one (e.g., between B and X ). [ 1 ] Estimate [ edit ] Transmission between two network nodes may be asymmetric, and the forward and reverse delays are not equal. Half the RTT value is the average of the forward and reverse delays and so may sometimes be used as an approximation to the end-to-end delay. The accuracy of such an estimate depends on the nature of the delay distribution in both directions. As delays in both directions become more symmetric, the accuracy increases. The probability mass function (PMF) of absolute error, E , between the smaller of the forward and reverse OWDs and their average (i.e., RTT/2) can be expressed as a function of the network delay distribution as follows: [ 1 ] Pr ( E = x ) = { ∑ i = 0 ∞ f i ( a ) . f i ( b ) , x = 0 , ∑ i = 0 ∞ f i ( a ) . f 2 x + i ( b ) + ∑ i = 0 ∞ f i ( b ) . f 2 x + i ( a ) , x > 0 , {\displaystyle \Pr(E=x)={\begin{cases}\displaystyle \sum _{i=0}^{\infty }f_{i}(a).f_{i}(b),&x=0,\\\displaystyle \sum _{i=0}^{\infty }f_{i}(a).f_{2x+i}(b)+\sum _{i=0}^{\infty }f_{i}(b).f_{2x+i}(a),&x>0,\end{cases}}} where a and b are the forward and reverse edges, and f y ( z ) is the PMF of delay of edge z (that is, f y ( z ) = Pr{delay on edge z = y }). Delay components [ edit ] End-to-end delay in networks comes from several sources including transmission delay , propagation delay , processing delay and queuing delay . See also [ edit ] Age of Information Minimum-Pairs Protocol Network delay Store and forward References [ edit ] ^ a b Abdou, AbdelRahman; Matrawy, Ashraf; van Oorschot, Paul (May 2015). "Accurate One-Way Delay Estimation with Reduced Client-Trustworthiness". IEEE Communications Letters . 19 (5): 735– 738. CiteSeerX   10.1.1.696.7425 . doi : 10.1109/LCOMM.2015.2411591 . S2CID   17100293 . External links [ edit ] Sample delay calculations Authority control databases International GND National United States Israel Retrieved from " https://en.wikipedia.org/w/index.php?title=End-to-end_delay&oldid=1337720774 " Category : Computer networking Hidden categories: Articles with short description Short description is different from Wikidata This page was last edited on 11 February 2026, at 02:35  (UTC) . Text is available under the Creative Commons Attribution-ShareAlike 4.0 License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy . Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. , a non-profit organization. Privacy policy About Wikipedia Disclaimers Contact Wikipedia Legal & safety contacts Code of Conduct Developers Statistics Cookie statement Mobile view Search Search Toggle the table of contents End-to-end delay 4 languages Add topic