Evaluating architectural patterns for SLA compliance involves analyzing how different hybrid interconnect topologies meet specific uptime guarantees, such as 99.9% or 99.99%. The evaluation focuses on the redundancy, configuration, and operational considerations of Dedicated Interconnect and Partner Interconnect within Google Cloud Platform. The goal is to choose a pattern that aligns with the required service-level agreement (SLA) by ensuring sufficient capacity and failover paths.
Dedicated Interconnect provides a direct, physical connection between a customer's on-premises network and Google's network through a shared colocation facility. This architecture requires the customer to own and maintain physical routing equipment in the facility. For SLA compliance, a single connection offers no uptime guarantee. To achieve an SLA of 99.9% or 99.99%, you must build a redundant topology.
A redundant Dedicated Interconnect setup for high availability involves multiple connections placed in specific locations. For a 99.99% SLA, Google's prescriptive configuration requires at least four VLAN attachments across two different metropolitan areas (metros), with one attachment in each of the two edge availability domains within each metro. You also need two Cloud Routers, one in each of two different Google Cloud regions for the same VPC network, with global routing enabled. Traffic flows from the VPC network to the on-premises network over these multiple paths, and if one path fails, the others continue to carry traffic. For a 99.9% SLA, the requirement is at least two connections and two VLAN attachments within a single Google Cloud region, but split across two different edge availability domains within the same metro.
Partner Interconnect uses a service provider's network to connect a customer's on-premises or other cloud environment to Google Cloud. The partner manages the virtual routing equipment that establishes BGP sessions between the Cloud Router and the remote gateway. Like Dedicated Interconnect, a single Partner Interconnect connection has no SLA. Redundant configurations are necessary for 99.9% or 99.99% uptime guarantees.
The architectural pattern for redundancy in Partner Interconnect mirrors that of Dedicated Interconnect but involves a third-party service provider. To achieve a 99.99% SLA, you need at least four VLAN attachments across two metros, with attachments in separate edge availability domains, paired with two Cloud Routers in different Google Cloud regions. The overall solution's reliability depends on three separate SLAs: one from Google for its infrastructure, one from the interconnect partner, and one from the other cloud provider (e.g., AWS or Azure). The 99.9% SLA configuration requires two VLAN attachments within a single region, placed in different edge availability domains of the same metro.
In both architectural patterns, building for an SLA means creating redundant connections that are isolated from simultaneous failures. The key concept is the edge availability domain: each metro has two such domains (zone1 and zone2), and scheduled maintenance is coordinated within a metro across these domains but not coordinated across different metros. Therefore, for the highest availability (99.99%), connections must be spread across two metros to avoid overlapping maintenance outages.
Once redundant paths are established, egress traffic from the VPC network to the on-premises network is load-balanced. Google Cloud uses Equal-Cost Multi-Path (ECMP) routing to distribute traffic across all active VLAN attachments, provided the Cloud Routers receive the same route advertisements with the same cost. The traffic is balanced based on the configured capacity of each VLAN attachment. A critical operational consideration is provisioning enough capacity on each redundant connection to handle the full production workload during a failover event. If one connection fails, the remaining connection must have sufficient attachment capacity to carry all traffic without loss.
Traffic over both Dedicated and Partner Interconnect is not encrypted by default. For SLA-compliant architectures that also require data security, you can deploy HA VPN over Cloud Interconnect. This adds IPsec encryption to the interconnect traffic without changing the underlying redundancy topology or its SLA. Alternatively, encryption can be applied at the application layer (e.g., using TLS). Some other cloud providers also offer managed VPN services over their interconnect products.
Choosing between Dedicated and Partner Interconnect for an SLA-bound architecture involves tradeoffs. Dedicated Interconnect typically offers the lowest latency and highest potential bandwidth (up to 100 Gbps connections) but requires significant customer investment in colocation facility contracts and physical hardware. It is cost-effective for very high, regular data transfer. Partner Interconnect simplifies the physical layer by using a service provider, with attachment capacities ranging from 50 Mbps to 50 Gbps. It is suitable when you lack presence in a Google colocation facility or require multicloud connectivity to a specific partner-supported cloud. However, its latency includes an extra hop through the partner's network, and the end-to-end SLA is a composite of multiple providers' guarantees. For pure cloud-to-cloud connectivity, Partner Interconnect is generally recommended unless you have specific needs for physical control or exceed partner capacity limits.
Monitoring and validating SLA performance metrics involves tracking the availability and performance of Cloud Interconnect connections to ensure they meet the contractual guarantees defined in service-level agreements. Google Cloud provides several tools and methodologies to monitor infrastructure, validate SLA compliance, and respond when performance metrics indicate potential breaches.
You can monitor the current status of Google Cloud services across all regions using the Google Cloud Service Health Dashboard, which provides real-time information about service health and any ongoing incidents. The dashboard also offers a historical view of infrastructure failures, including details such as incident duration, affected zones and regions, affected services, and recommended workarounds. For project-specific monitoring, Personalized Service Health lets you view incidents relevant to your own projects and can be configured to send alerts when issues affect your resources. Google provides regular updates about the status of each incident, including estimated times for the next update, and you can programmatically retrieve status updates through an RSS feed.
Cloud Monitoring automatically collects and stores performance information for most Google Cloud services, including Cloud Interconnect. You can track critical interconnect metrics such as packet loss, latency, and availability by creating alerting policies that define threshold conditions and notification channels. The alerting service supports common notification channels including email, Cloud Mobile App, and third-party services such as PagerDuty or Slack. When creating an alerting policy, you specify a condition type and threshold, add notification channels, and define an incident autoclose duration that determines when Monitoring closes incidents in the absence of metric data.
To create custom Monitoring dashboards for Cloud Interconnect metrics, you can add custom charts that display the specific metrics and filters relevant to your interconnect topology. Cloud Interconnect metrics are available through the Monitored resource types and Metrics list documentation. Network Topology provides an additional visualization capability that overlays throughput values on each connection, allowing you to quickly see the amount of traffic traversing the VLAN attachment that connects Google Cloud to an on-premises network. Metric values in Network Topology are based on the final five minutes of the selected hour, and you can view historical data for up to six weeks.
Google Cloud infrastructure is designed to support target availability levels that form the basis for SLA commitments: single-zone deployments target 99.9% availability (approximately 43.2 minutes maximum monthly downtime), multiple zones in a region target 99.99% availability (approximately 4.3 minutes maximum monthly downtime), and multiple regions target 99.999% availability (approximately 26 seconds maximum monthly downtime). The availability percentages in these targets are goals, and the uptime SLAs for specific Google Cloud services may differ from these availability targets. For example, the uptime SLA for a Bigtable instance depends on the number of clusters, their distribution across locations, and the routing policy configured.
The aggregate availability that you can expect from an infrastructure stack depends on Google Cloud SLAs, resource redundancy, and stack depth. Aggregate availability is calculated by multiplying the availability of each tier in the application stack—for example, if each tier provides 99.9% availability, the aggregate availability is 99.6% (0.999 × 0.999 × 0.999 × 0.999). This means the aggregate availability of a multi-tier stack is typically lower than the availability of the tier that provides the least availability. Where feasible, choosing parallelization over chaining results in higher end-to-end availability because parallelized services do not multiply their availability degradation the same way chained services do.
To validate that your deployed topology meets contractual availability guarantees, you should establish Service Level Indicators (SLIs) that directly measure the behavior of your services, Service Level Objectives (SLOs) that define target availability levels, and error budgets that track remaining availability allowance. You can use SLI data to monitor whether systems are within defined SLOs and to ensure that SLAs are met. Engineers can monitor FSI applications at the service level directly within the deployment environment (such as GKE or Cloud Run) or by using logs provided by infrastructure components like load balancers. OpenTelemetry provides an open-source standard for capturing telemetry including metrics, traces, and logs, while Google Cloud Managed Service for Prometheus provides a fully-managed backend for metrics and Prometheus operations at scale.
Proactive monitoring and validation through synthetic monitors allows you to test the availability, consistency, and performance of your services, applications, and APIs. You can create uptime checks that probe HTTP, HTTPS, and TCP endpoints for responsiveness and notify you when an endpoint fails to respond. This approach lets you detect issues before end users experience them and provides evidence of SLA compliance or breach that can be used for service credit requests.
Designing redundant interconnect configurations is the practice of creating multiple, independent connection paths between Google Cloud and your on-premises network to meet high availability service-level agreements (SLAs) like 99.9% and 99.99%. This involves using Cloud Interconnect services—Dedicated Interconnect or Partner Interconnect—to establish physical links, and then configuring logical and routing layers to eliminate single points of failure. The goal is to ensure that if one path fails, traffic automatically and seamlessly switches to another without service disruption.
A redundant interconnect design requires creating multiple, separate VLAN attachments across different Interconnect connections. Each VLAN attachment is a logical connection that carries your network traffic over a physical Interconnect link. For 99.9% or 99.99% SLAs, you must create at least two VLAN attachments on physically diverse Interconnect connections—either two separate Dedicated Interconnect circuits or two distinct Partner Interconnect connections through different service providers. These attachments should terminate in different Google Cloud point-of-presence (PoP) locations or use different edge availability domains when possible. This ensures that a failure in one physical link, cable, or Google networking device does not take down your entire hybrid connectivity.
After establishing redundant VLAN attachments, you configure Border Gateway Protocol (BGP) sessions over them to manage how traffic routes between your on-premises network and Google Cloud. For active-active redundancy, you establish BGP sessions on all VLAN attachments simultaneously, allowing traffic to load balance across all available paths. For active-passive redundancy, you configure primary and secondary BGP sessions; the secondary session remains established but with a higher route priority (lower Local Preference), so it only carries traffic if the primary path fails. You must configure multiprotocol BGP (MP-BGP) to support both IPv4 and IPv6 address families if your design requires dual-stack connectivity. The Cloud Router service manages these BGP sessions on the Google Cloud side, exchanging routes with your on-premises router.
The final, critical step is to verify that the entire interconnect path—from your on-premises router to your Google Cloud Virtual Private Cloud (VPC) network—has no shared failure points. This means checking that the physical Interconnect connections use separate cables, cross-connects, and Google router ports. You should also confirm that the VLAN attachments are provisioned on different edge availability domains or from distinct Interconnect bundles. Operationally, you use tools like the Interconnect diagnostics and Cloud Monitoring to validate the health and independence of each path. Without this end-to-end path diversity, a single failure could still impact both redundant connections, preventing you from achieving the target SLA.
Dedicated Interconnect provides a direct physical connection through a colocation facility, offering lower latency and bandwidth up to 100 Gbps, but requires customer-owned hardware and facility contracts. Partner Interconnect uses a service provider's network, with capacities from 50 Mbps to 50 Gbps, and is simpler to set up but adds an extra network hop and a composite SLA from multiple providers. Both require the same redundant topology (VLAN attachments across edge availability domains and metros) to achieve 99.9% or 99.99% SLAs.
Aggregate availability is the product of the availability percentages of each tier in the stack. For example, if each of four tiers offers 99.9% availability, multiply 0.999 × 0.999 × 0.999 × 0.999 to get approximately 0.996, or 99.6% aggregate availability. This means the overall availability is lower than the least available tier. Using parallelized services instead of chained services can improve end-to-end availability.
You can use the Google Cloud Service Health Dashboard for real-time and historical incident data, and Personalized Service Health for project-specific alerts. Cloud Monitoring collects interconnect metrics like packet loss and latency; you can create alerting policies with threshold conditions and notification channels. Network Topology visualizes throughput on VLAN attachments. For proactive validation, create uptime checks (HTTP, HTTPS, TCP) as synthetic monitors to test endpoint responsiveness and detect issues before users are affected.
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