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Difficulty: HardOptimizing Network Performance and Latency

A global high-frequency trading SaaS platform operates its core transactional backend in the us-east-1 Region. The system connects to an on-premises colocation facility using a 10 Gbps AWS Direct Connect connection terminated on a Direct Connect Gateway (DXGW) via a Transit Virtual Interface (Transit VIF) attached to an AWS Transit Gateway in us-east-1. The platform is expanding its analytical services to the us-west-2 Region, where EC2 instances in multiple VPCs are connected via a local Transit Gateway in us-west-2. The Transit Gateways in both regions are peered.

Analytical applications in us-west-2 must transfer large, time-sensitive datasets (up to 120 GB per file) directly to the on-premises colocation facility. Currently, the team has configured routing to send traffic from the us-west-2 VPCs through their local Transit Gateway, across the inter-region Transit Gateway peering connection to the Transit Gateway in us-east-1, and then to the DXGW. However, network administrators report that traffic from us-west-2 cannot establish connectivity to the on-premises network. Furthermore, once connectivity is resolved, the company requires the configuration to deliver the highest possible throughput and lowest latency, utilizing jumbo frames.

Which combination of actions will resolve the connectivity issue while optimizing throughput and latency for the data transfers?

  1. Associate the existing Direct Connect Gateway directly with the Transit Gateway in us-west-2. Update the VPC route tables in us-west-2 and the us-west-2 Transit Gateway route tables to route the on-premises IP ranges directly to the Direct Connect Gateway attachment. Configure the MTU on the EC2 instances in us-west-2 to 8500 bytes.Answer
  2. B
    Keep the existing inter-region Transit Gateway peering connection. Enable transitive routing on the Transit Gateway in us-east-1 to allow traffic coming from the peered us-west-2 Transit Gateway to be forwarded to the Direct Connect Gateway. Configure the MTU on the EC2 instances in us-west-2 to 9001 bytes.
  3. C
    Create a Route 53 Private Hosted Zone containing the on-premises database endpoints, and associate it only with the VPCs in us-east-1. Deploy a fleet of EC2-based proxy instances behind an Application Load Balancer in us-east-1 to forward traffic from us-west-2 to the on-premises network. Route the traffic from the us-west-2 VPCs through the Transit Gateway peering connection to the proxy fleet.
  4. D
    Configure a software VPN connection from the EC2 instances in us-west-2 through a single NAT Gateway in us-west-2 to the on-premises VPN device, routing over the public internet to bypass the Transit Gateway peering link. Configure the MTU on the EC2 instances in us-west-2 to 9001 bytes and enable path MTU discovery (PMTUD).

Answer

Associate the existing Direct Connect Gateway directly with the Transit Gateway in the us-west-2 Region, route the traffic directly to the Direct Connect Gateway attachment, and configure the EC2 instances to use an MTU of 8500 bytes.
Associating the Direct Connect Gateway directly with the Transit Gateway in the second region establishes a direct routing path over the AWS Direct Connect connection. This avoids the Transit Gateway transitive routing limitation where a peered Transit Gateway cannot route traffic to a local Direct Connect Gateway. Furthermore, configuring the EC2 instances to use an MTU of 8500 bytes matches the maximum jumbo frame MTU supported by Direct Connect Transit VIFs and Transit Gateway, avoiding packet drops and optimization issues.

Step-by-Step Solution

1
Associate the existing Direct Connect Gateway with the Transit Gateway in us-west-2.
This creates a local attachment between the Transit Gateway in us-west-2 and the global Direct Connect Gateway, enabling a direct path to the on-premises network.
AWS Transit Gateway does not support transitive routing between peered Transit Gateways and a Direct Connect Gateway. Directly associating the Direct Connect Gateway with the local Transit Gateway resolves this connectivity limitation.
2
Update the VPC route tables in us-west-2 and the local Transit Gateway route tables to forward on-premises traffic to the Direct Connect Gateway attachment.
Traffic destined for the on-premises network is routed directly to the Direct Connect Gateway attachment rather than through the peering link.
This establishes the data path locally and avoids traversing the inter-region peering connection, reducing latency.
3
Configure the MTU on the EC2 instances in us-west-2 to 8500 bytes.
The network interface on the instances is configured to send jumbo frames up to 8500 bytes.
AWS Direct Connect Transit VIFs and Transit Gateways support a maximum MTU of 8500 bytes. Setting this value optimizes throughput by using jumbo frames without causing packet drops or fragmentation.

Key Concept

AWS Transit Gateway inter-region routing limitations and Direct Connect Gateway multi-region associations with jumbo frame (MTU) optimization.
Estimated Time:3m 0s
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Topics

Optimizing Network Performance and Latency