DNS plays the ‘phone book’ role in the internet world. As multi-cloud setup has become more and more prevalent for enterprise customers. The Integration of customer-owned on-premise networks with cloud-based infrastructures to provide a seamless domain name resolution experience is vital to customers’ enterprise landscapes.
link to guide for Azure: here
link to guide for GCP: here
In this article, we are addressing such scenarios, where SAP RISE customers have their SAP workloads hosted on SAP managed cloud environment (on Azure, AWS, GCP, or SAP Data Center), while might also have one or both of: their own on-premise data centers, and their own hyperscalers (Azure, AWS, or GCP) subscription. And each network environment has its own DNS setup. Chaos might occur if domain names or IP ranges were not properly routed.
Thereby, we are proposing a reference architecture for such scenarios to resolve DNS requests coming from all sources (SAP RISE managed environments, on-premise data center DNS servers, and customer’s own hyperscalers DNS services), with disaster recovery been considered.
Terminologies and Abbraviations
DNS: short for Domain Name System. It translates between domain names (like *.ecs.sap.com) and IP addresses (like 192.168.1.1 in IPv4, 2400:cb00:2048:1::c629:d7a2 in IPv6) in both ways.
DNS Zone Transfer: [SAP RISE preferred] one of the mechanisms to replicate DNS databases across a set of DNS servers. SAP RISE recommends this because of: its high availability; it provides redundancy and higher SLA, especially for DR scenarios; it can establish reliable status monitoring. The disadvantage is: DNS Notifiers should be in place to ensure the full DNS TTL Delay.
DNS Conditional Forward (or so-called ‘IP Forward’): DNS servers that only forward queries for specific domain names. The advantage is, if no outbound traffic from SAP RISE is necessary, customers do not have to configure their own DNS for their inbound traffic. The disadvantages are: customer OP DNS may suffer delay due to forward cache (but configurable); also due to forward cache, failover could take more time, hence diminishing SLA; limited status monitoring.
Zone Delegation: a process of assigning authority over a domain or subdomain to different DNS servers to keep records updated. The advantage is: customers can manage OP DNS through SAP RISE as a single point. The disadvantages are: configuration is onerous; lower performance due to increased DNS traffic; diminished SLA.
Consensus / Prerequisites
- Only server-side DNS servers are been considered in this reference architecture, client-side DNS (if any) are not been addressed here
- Disaster recovery on customer’s data center is not been considered
- Network connections for pairing virtual networks or connecting on-premise networks with the cloud (like VPC peering, VNet peering, VPN, .etc), and other network components (like load balancer, .etc.) are not been addressed in this reference architecture. Separate reference architectures will be created in later blog series.
- SAP RISE DNS servers are seen as resources, and each standard virtualized DNS cluster deployed within a zone contains 2 DNS servers for HA.
- DNS services on customer’s own hyperscalers are seen as services, and customers should ensure HA/DR been enabled on service level
- In DR cases, we call it by zone, instead of region, since RISE customers can may deploy SDDR (different zones within the same region), or LDDR (in different regions)
- The offerings by hyperscalers (Azure, AWS, and GCP) are based on the services’ general availability of hyperscalers providers’ (Microsoft, Amazon, and Google) official documentation online, as of this blog’s publishing date of time The offerings by SAP RISE are based on SAP ECS service guidance as of this blog’s publishing date of time
on customer’s AWS subscription side:
Option 1: AWS DNS is server deployed on AWS EC2 (see Fig. 1 and Fig. 2)
- zone transfer (SAP RISE preferred DNS integration approach) is applied to do DNS integration
Option 2: AWS DNS is AWS DNS services (see Fig. 3 and Fig. 4)
- Route53 resolver based on Route53 is been used to integrate DNS from another peered VPC (eg. RISE DNS on SAP-managed AWS VPC), OP network that is connected to AWS with AWS Direct Connect, a VPN, or a network address translation (NAT) gateway
- dedicated inbound endpoint and outbound endpoint are been deployed to connect each peered VPC or connected OP network
- IP forward is applied to do information exchange with RISE DNS and OP DNS
- in DR case, Route53 setup is shared by 2 VPCs from main zone and DR zone
- In DR case, Route53 can be used to configure DR mechanism
on SAP RISE subscription side:
- RISE DNS cluster (contains 2 DNS servers) is been deployed within the same virtual private cloud as SAP-managed VMs
- RISE DNS shares information with OP DNS through DNS zone transfer
- In DR case, a DNS cluster is deployed in each zone, the 2 DNS clusters share information through DNS zone transfer
on customer’s data center side:
- OP DNS can optionally share some information with RISE DNS through DNS conditional forward
Fig. 1: Reference architecture for DNS integration when customer’s AWS DNS is server on AWS
Fig. 2: Reference architecture for DNS integration with DR considered when customer’s AWS DNS is server on AWS
Fig. 3: Reference architecture for DNS integration when customer’s AWS DNS is AWS service
Fig. 4 Reference architecture for DNS integration with DR considered when customer’s AWS DNS is AWS service
- SAP takes no responsibility for managing and operating customers’ own data center, nor for customers’ own hyperscaler subscription
- RISE customers should provide corresponding DNS information, with regard to SAP ECS guidance
- RISE customers should be aware of the pros and cons of the selected DNS integration approach
Acknowledgment to contributors/reviewers/advisors:
Ke Ma (a.k.a. Mark), Senior Consultant, SAP IES AI CoE / RISE with SAP RA group
Kevin Flanagan, Head of SAP RISE CAA EMEA North
Richard Traut, Cloud Architect Expert, SAP RISE CAA
Darrell Lee, Cloud Architect Expert, SAP RISE CAA
Luc DUCOIN, Cloud Architect Expert, SAP RISE CAA
Sven Bedorf, Head of SAP RISE CAA MEE
Jyothi Prakash Lakshmi, Network Engineer, SAP ECS
Frank Gong, Digital Customer Engagement Manager, SAP ECS