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Cloud Services/Cloud WAN & Networking

01CLOUD SERVICES · CLOUD WAN & NETWORKING

The global network,
delivered as a product.

Global networks are where cloud programs stall — hand-built, region by region, understood by two people. CAELION’s network practice designs the AWS core network on AWS Cloud WAN and delivers it as parameterized infrastructure-as-code: segmented, automated, and observable from day one. Migrations from Transit Gateway are sequenced for zero downtime, one routing domain at a time.

Discuss your network All cloud services

CLOUD WAN / TRANSIT GATEWAY / DIRECT CONNECT / SD-WAN0 downtime target · 100% as IaC

02THE NETWORK PRACTICE

Four disciplines. One core network.

Core network design, Transit Gateway migration, hybrid connectivity, and network automation — engineered as one estate, not four projects. Everything below ships as parameterized infrastructure-as-code that your team owns.

Core Network Design · Segment Policy

Segment policy is the architecture.

AWS Cloud WAN turns the global network into a managed core with policy at its center. We treat that policy document as the primary engineering artifact — written, reviewed, and versioned before a single attachment is made.

  • Segments with intent — production, non-production, shared services, partner, regulated: each an explicit isolation boundary with a written rule for what may talk to what. Isolation is designed, not discovered.
  • Global routing, one control plane — route propagation, inter-segment sharing, and inter-region behavior defined once, centrally, instead of reconstructed per-region from tribal knowledge and route-table archaeology.
  • Observable from day one — flow visibility, segment health, and routing state instrumented as part of the build, and queryable in plain English through Meridian once the practice’s agentic layer is connected.
AWS Cloud WANSegment policyGlobal routingFlow visibility
Discuss your core design →

Transit Gateway → Cloud WAN

Migration sequenced for zero downtime.

You do not cut over a global network in a weekend. You cut it over one routing domain at a time, with the old and new networks running in parallel and a rehearsed rollback at every step.

  • The Cloud WAN core is stood up alongside the existing network, as code — nothing production-facing changes until validation passes.
  • Routing domains move one at a time; traffic is validated before and after each move, and every step is independently reversible.
  • The blast radius of any surprise is one segment — never the enterprise. Transit Gateway is retired only after the new core has carried production traffic cleanly.
Transit GatewayParallel buildStaged cutoverRehearsed rollback
Plan your cutover →

Hybrid Connectivity · DX / SD-WAN

Data centers and SD-WAN, into the same core.

The core network only matters if everything reaches it. We design hybrid connectivity as part of the same architecture — not an afterthought bolted to the edge.

  • Direct Connect design: resiliency model, virtual interfaces, failover behavior tested — not assumed.
  • SD-WAN fabric integration into Cloud WAN segments, preserving your branch investment.
  • Site-to-site VPN as engineered backup paths with defined failover characteristics.
  • Bandwidth, latency, and cost modeled per path before anything is provisioned.
Direct ConnectSD-WANSite-to-site VPNFailover tested
Discuss hybrid architecture →

Automation · Network as Code

Parameterized IaC. Yours to keep.

Every deliverable ships as parameterized CloudFormation or Terraform that your team owns, reviews, and re-runs. The network stops being a snowflake and becomes a codebase.

  • Multi-region, multi-account rollout driven from one parameterized module set.
  • New region, account, or segment = a parameter change and a pull request, not a project.
  • Segment policy versioned and testable before it is applied.
  • Full handover: your engineers can operate and extend the network without us.
CloudFormationTerraformMulti-accountFull handover
Talk automation →

03THE CUTOVER METHOD

You do not cut over a global network in a weekend.

“One routing domain at a time — old and new networks in parallel, a rehearsed rollback at every step.”

01

Assess

Model the current Transit Gateway estate — attachments, routing domains, propagations, blackholes, hybrid links, and the dependencies nobody documented — into a migration plan reviewed with your team.

02

Parallel core build

The Cloud WAN core network is stood up alongside the existing network — as code — with segments, policy, and hybrid attachments in place. Nothing production-facing changes yet.

03

Staged cutover

Routing domains move one at a time, each step independently reversible. The blast radius of any surprise is one segment — never the enterprise.

04

Validate & evidence

Traffic is validated before and after every move, against a rehearsed rollback. A domain is done only when it carries production traffic on Cloud WAN with clean validation.

05

Decommission & handover

Transit Gateway attachments and peerings are retired only after the new core has carried production traffic cleanly — ending double-run costs. Final architecture and runbooks handed over.

04EXIT CRITERIA, NOT STATUS UPDATES

Every phase ends with proof. Not a slide.

Each phase of a Transit Gateway → Cloud WAN migration has written exit criteria agreed with your team up front. A phase is complete when the criteria are met — validated on production traffic, with the rollback story rehearsed — not when the calendar says so.

MIGRATION GATES · TGW → CLOUD WANPER PHASE
01.assesscomplete dependency map · segment design agreed · per-domain cutover order fixed
02.parallel_buildcore network live and validated · policy tested · rollback rehearsed
03.cutovereach domain carrying production traffic on Cloud WAN with clean validation
04.decommissionlegacy estate removed · final architecture and runbooks handed over
0
Downtime target
4
Phases, each with rollback
1 SEG
Blast radius per step
100%
Shipped as IaC you own

05QUESTIONS, ANSWERED PLAINLY

What network teams ask us first.

How do you migrate from Transit Gateway to Cloud WAN without downtime?
Four phases: Assess (model the current Transit Gateway estate, routing domains, and undocumented dependencies), Parallel build (stand up the Cloud WAN core alongside the existing network, as code), Segment-by-segment cutover (move one routing domain at a time, validating traffic before and after each move, with a rehearsed rollback for every step), and Decommission (retire Transit Gateway only once the new core has carried production traffic cleanly). Every phase targets zero downtime, and the blast radius of any step is one segment.
What does segment policy design actually involve?
Segments are the isolation and routing boundaries of the core network — production, non-production, shared services, partner, and regulated workloads each get an explicit segment with a written rule for what may talk to what. We express the entire policy document as reviewable code, so network intent is versioned, auditable, and testable before it is applied.
Do you handle hybrid — Direct Connect and SD-WAN?
Yes. We design and deliver hybrid architectures that bring data centers, offices, and existing SD-WAN fabrics into the AWS core network over Direct Connect and site-to-site VPN — with routing, failover, and bandwidth planned as part of the same core network design, not bolted on afterward.
What does “network as parameterized IaC” mean in practice?
Every deliverable — core network, segments, attachments, routing policy, hybrid connections — ships as parameterized CloudFormation or Terraform that your team owns and can re-run. Adding a region, an account, or a segment becomes a parameter change and a pull request. At handover, your engineers can operate and extend the network without us.

06RELATED SERVICES

The practice around the network.

EXPERTISE

AWS Professional Services & Expert Hub

Well-Architected reviews with remediation delivered, landing zones, migration and modernization — a named senior bench, no pyramids.

Cloud Services →

OPERATIONS

Managed Cloud Operations (PODs)

After go-live, 24×7 follow-the-sun pods operate the estate — continuous FinOps, posture, drift correction, and incident response.

Cloud Services →

PLATFORM

Agentic Cloud Operations (Meridian)

Query every VPC, route, and security group in plain English — evidence-backed answers in ~5 seconds across the whole estate.

Cloud Services →

Bring us the network diagram nobody trusts.

In one working session, our network architects review your current Transit Gateway estate and sketch the Cloud WAN target — with the migration sequence and the rollback story for every step.

Request a network review All cloud services

Zero-downtime sequencing · One routing domain at a time · 100% parameterized IaC