You just eliminated 28 rooms from your search. The first range satisfies your 917 room, so you go left. The input is known, you know your room number, you do a quick check on the two ranges. The rooms to the right a different range is 939–967. The rooms to the left presents a range 916–937. Now that you got to your floor you hit a fork in the road with a sign in the middle. You just went immediately to your floor, without this knowledge you would have searched every floor in the hotel to find your room. This means your room is on the 9th floor. The first step is to find which floor your room is at, usually the first digit represents the floor. This helps finding rooms convenient and fast especially if the hotel has many rooms. If you’ve been to a hotel often you would see a sign looking something like this on the way to your room. How does this Las Vegas hotel floor room sign related to Database indexing? let me explain #backendengineering #rfc #softwarearchitecture #networking #ipv6 #ipv4 #dns #envoy If both IPv6 and IPv4 paths are working, the IPv4 connection is abandoned in favor of the IPv6 connection (Figure 3)įrom what I understood, The goal is encourage implementations to rely on IPv6 more so that IPv4 traffic will eventually be reduced as IPv6 networks become more reliable. This is the second image (Figure 2 in the RFC) If the IPv6 path is broken, the communication continues with IPv4. The Happy Eyeballs RFC proposes establishing a TCP connection to both IPv6 and IPv4 addresses at the same time. This causes significant delays in the application (Figure 1) up to a few seconds. If that timeout is reached it then switches to IPv4. The client will first attempt to connect to the IPv6 end point (if available) and when it fails to connect, it keeps retrying for few seconds (TCP SYN retry). When a client that support both IPv6 and IPv4 does a DNS query, it asks for both IPv4 and IPv6 addresses. This can cause problems when communicating in IPv6 backends if the intermediate routers/nodes do not have full support for the protocol or even if the server implementation is faulty. While IPv6 is the next evolution of the Internet protocol that supports a larger number of IP addresses and has many features, support for it has been slow in the Internet. Intrigued by the name, I read the document and learned something new so here is my summary. I was reading on Envoy's listener and threading architecture (A comment in Linkedin peaked my interest on the topic) and noticed that Envoy implements RFC 6555 named Happy Eyeballs. I randomly stumble upon many topics during the day and if a desire to learn from my part exists I pursue it. A possible logical extension would be implementing the algorithm in other applications.I get asked this a lot, Hussein how do you decide upon the topics you write about? The truth is murky and unclear to me. Possible extensionĪt the moment happy eyeballs relates to the web browser. Referring to the web browser, what happy eyeballs does is introducing a different TCP behavior after a response to the DNS query is received.īoth IPv6 and IPv4 syn packets are sent off at the same time, the first syn-ack that reaches the source will determined the protocol used and the other one will be discarded. There is clearly too much “waiting time”! Happy eyeballs algorithm Only when TCP is sure that this tentative of connection has failed will send the IPv4 (or IPv6) syn. In a dual stack connection model, an IPv6 (or IPv4) syn will first be sent. The introduction of the dual stack environment, which deals with both IPv4 and IPv6 addresses, has made this performance issue worse. He main issue here is that if the syn-ack gets lost or is not sent at all, TCP keeps waiting slowing down all applications that are related to that connection. The behavior happy eyeballs is trying to improve is generated by how the TCP handshake protocol works.īefore establishing a connection and after sending a syn packet, TCP waits a syn-ack packet from the counterpart. The idea of Happy eyeballs was first introduced as improvement to the responsiveness of the dual-stack applications (both IPv4 and IPv6).
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