University:
York University
Course:
AP/ITEC 1610 | Introduction to Computer Programming
Academic year:

2023
Views:

370

Pages:

2
Author:

Nick T.

DOMAIN NAME SYSTEM →core internet function Distributed database implemented in hierarchy of many name servers •An application layer protocol: provides applications (web browsers, email dients). a service that use to translate human readable domain names into IPaddresses. • Occurs at networle edge DNS Services hostname-to-IP-address host aliasing (canonical-subdomain, alias - many names mail server for same address) - aliasing-email addresses all pointing to the same server •load distribution: distribute traffic among replicated web servers CANNOT BE CENTRALIZED Bulletproof reliability and security Root servers: responsibly for queries at highest level of DNS when nearby: severs don't lenow, pass to Root Top Level Domain servers responsible for .com, .net, .org. root server sends query to related TLD Authoritative DNS Servers: organizations servers authoritative hostname to I Pmapping for orgs. named hosts Local DNS server: if unable to provide IP, forward to hierarchy Iterated Query: Each server in hierarchy send bacle next step to local server Recursive Query: Each server talks to the nexts and send final IP back down the chain of communication Server always caches any mapping it lears DNS records RR (resource records) format: (name, valve, type, (tl) Types: A name=hostname, valve = IP address NS: name = domain (foo.com), value = hostname of auth name server CNAME: name alias, value = canonical (true) nume MX: valve name of mail server associated with name ← z bytes TO 2 byles → flags header ID: same for QandA: 16bit # questions # answers RR flags: query/reply, recursion? #authority PRS #additional RRS questions name, type fields for a query answers → RRs in response to queries authority → records for auth servers additional info →helpful info