Tuesday, December 18, 2018

Oracle Cloud Infrastructure―OCI DNS Service Basics

Founded on Dyn’s DNS, the Oracle Cloud Infrastructure (OCIDNS service (DNS) is an integral part of Oracle Cloud Infrastructure’s suite of edge services. It’s available through the Oracle Cloud Infrastructure Console and the API.
Oracle Cloud Infrastructure (OCI) customers can configure DNS names for their instances in the Virtual Cloud Network (VCN) as described in DNS in Your Virtual Cloud Network. The DNS names are resolvable only within the VCN using the VCN DNS resolver available at 169.254.169.254. This IP address is only reachable from instances in the VCN.

Figure 1.  Domains and sub-domains correspond to nodes in the tree

Figure 2. Parent zones and child zones, which may overlap


Domains and Zones


A DNS zone is the part of a domain for which an individual DNS server is responsible. 

The term domain is used in the business functions of the entity assigned to it and the term zone is usually used for configuration of DNS services.  In other words, domain name is used in business for naming purpose and DNS zones are used from the administrative and management perspective. From Figure 1 and 2, you can see how closely are domains/subdomains and parent/child zones mapped to each other.

In Figure 1, domains or sub-domains corresponds to the nodes of tree. In OCI terminology, the "www" section of www.xyz.com or the "eng" and "dev" sections of dev.eng.xyz.com are also known as labels.

In Figure 2, zones are administrative areas represented as circles on the diagram.  Each registration or allocation of subdomain space obligates the registrant to maintain an administrative and technical infrastructure to manage the responsibility for its zone, including sub-delegation to lower-level domains.

Finally, child zones are independent subdomains with their own Start of Authority (SOA) and Name Server (NS) records. The parent zone of a child zone must contain NS records that refer DNS queries to the name servers responsible for the child zone. Each subsequent child zone creates another link in the delegation chain.

DNS Service Capabilities and Limits


The DNS service provides dynamic, static, and recursive DNS solutions for enterprise customers. It provides the following features:
  • Operates on a global anycast network 
    • With 18 points of presence (PoPs) on five continents and offers fully redundant DNS constellations and multiple Tier 1 transit providers per PoP. 
  • Provides a DNS-based Distributed Denial of Services (DDoS) protection 
    • Also provides Oracle in-house security expertise that leverages a vast sensor network that collects and analyzes over 240 billion data points per day. 
  • Can function either as a primary or secondary DNS service
    • Fully supports the secondary DNS features to complement the customer’s existing DNS service, providing resiliency at the DNS layer.

For DNS Service, the Oracle Cloud Infrastructure has below limits:
  • DNS service is limited to 1000 zones per account and 25,000 records per zone
    • Customers with zone and record size needs exceeding these values are encouraged to contact support at support.oracle.com. 
  • Zone file  (see details below) uploads are limited to 1 megabyte (MB) in size per zone file
    • If your zone file is larger than 1 MB, you will need to split the zone file into smaller batches to upload all of the zone information.

How to Bring Your Domain Name to Oracle Cloud Infrastructure’s Edge Services


The OCI Domain Name System (DNS) service lets you create and manage your DNS zones. You can create zones, add records to zones, and allow Oracle Cloud Infrastructure's edge network to handle your domain's DNS queries.

For the step-by-step instructions of bringing your domain name to OCI's Edge Services, you can:
  • Read [5], a written version
  • Watch [2], a video version

DNS Zone Records

DNS Zone Management


DNS zone management  helps you to create and manage your DNS zones and zone records in Oracle Cloud Infrastructure.  Here we will discuss the details of OCI supported resource records.

DNS (Domain Name System) records are what make a domain name such as www.castro.cloud point to a webserver’s IP address like 129.213.163.103, etc. We need the DNS system and its records to keep the internet functioning and connected. A, CNAME, NS and SOA records described below are but a few of the types of records that can be used by your domains:
  • A Records
    • An A record (Address Record) points a domain or subdomain to an IP address.
  • CNAME Records
    • A CNAME (Canonical Name) points one domain or subdomain to another domain name, allowing you to update one A Record each time you make a change, regardless of how many Host Records need to resolve to that IP address.
  • NS Records
    • NS records are usually set with your registrar, and are used to delegate a domain or subdomain to a set of name servers.
  • SOA Records
The Oracle Cloud Infrastructure DNS service supports many other resource record (RR) types. For the full list of them, read [11].

Zone File


A zone file is a text file that describes a DNS zone. The BIND file format is the industry preferred zone file format and has been widely adopted by DNS server software. The format is defined in RFC 1035.  

To understand more on the DNS System and its records, you can download zone file from OCI's DNS service.  For example, you can read [14] for how to download it from Dyn’s Managed DNS.  For other details of zone file, you can read [12].

References

  1. DNS Zones (Wikipedia)
  2. OCI Level 100 - DNS (YouTube)
  3. Overview of the DNS Service (OCI)
  4. Oracle Cloud Infrastructure Blog
  5. Bring Your Domain Name to Oracle Cloud Infrastructure’s Edge Services
  6. Dyn’s DNS
  7. Domain providers
  8. Domain Name System (DNS) Delegation – The Zone Authority Chain
  9. Oracle Cloud Infrastructure Forum
  10. Managing DNS Service Zones (OCI)
  11. Supported Resource Records (OCI)
  12. Formatting a Zone File (OCI)
  13. Oracle Cloud Infrastructure User Guide (pdf)
  14. Download Your Zone File (Oracle Dyn)
  15. Oracle Cloud Infrastructure Documentation (Official Documentation)
  16. IaaS - Enterprise Cloud - Oracle Cloud Infrastructure (YouTube playlist)
  17. OCI Level 100 Training (YouTube playlist)
  18. OCI Level 200 Training (YouTube playlist)
  19. Oracle Cloud Infrastructure (redthunder.blog) 
  20. More articles on OCI (XML and More)
  21. Security Services and Features (OCI)
  22. Hybrid DNS Configuration (OCI)
    • This document describes the process to enable resolution of DNS names of instances in the VCN from on-premises clients and vice-versa, when the on-premises datacenter is connected with the VCN (through VPN or FastConnect).
  23. Access to Your On-Premises Network (OCI)
  24. DNS Checker 

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