CS138-lecture-20210225

Domain name system #

image_2021-02-25-09-28-12 image_2021-02-25-09-29-19 image_2021-02-25-09-37-21

DNS is a application layer service, it is run at the network edge.

image_2021-02-25-09-42-03 image_2021-02-25-09-44-34 image_2021-02-25-09-48-50 image_2021-02-25-09-57-26 image_2021-02-25-09-59-10 image_2021-02-25-09-30-39 image_2021-02-25-09-29-51

ttl = “time to leave”, expiration time
NS = name server, this is the point of contact
CNAME = canonical name, this is where you can specify a smaller name for a long name
MX = mailserver

image_2021-02-25-10-11-15

Query and response are the same format.

image_2021-02-25-10-12-37

dig asks for the IP address of a site.

image_2021-02-25-10-14-22