This page is being retained for historical purposes, but is no longer maintained. All relevant Direct Connect information about the current (2023 and after) Direct Connect architecture has been migrated to primary customer Direct Connect documentation, Cornell AWS Direct Connect. |
Executive Summary
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This document provides details about the Direct Connect architecture migration Cornell will be executing in early 2023. |
Cornell AWS accounts using Direct Connect for private access to Cornell networks will be transitioned to using Internet 2 Cloud Connect (I2CC) as the Direct Connect provider.
The Internet 2 Direct Connect provider offers several benefits:
As of , 65 Cornell AWS accounts were configured to use Direct Connect. During this migration, all those AWS accounts will have their existing Direct Connect connectivity updated to use new pathways and AWS resources to connect the Cornell campus network to AWS.
Within those 65 Cornell AWS accounts, only the network resources within VPCs using Direct Connect will be affected. Other VPCs in those Cornell AWS accounts will not be affected.
For VPCs using Direct connect, the following table identifies the impact of this migration on specific types of network traffic
Connectivity | Changing? |
---|---|
VPC connectivity to the Internet | not changing |
VPC-to-VPC peering | not changing |
VPC to campus addresses via the Direct Connect |
|
VPC to campus addresses via the Internet | not changing |
We use the following terminology in this document:
These diagrams show the network resources within Cornell AWS accounts that connect a VPC to the Cornell campus network via Direct Connect.
draw.io source: dc-arch-legacy.customer.v2.drawio
Resource | Filtering | |
---|---|---|
Source | Direct Connect Virtual Interface | — |
↓ | Virtual Private Gateway | — |
↓ | NACL of Subnet containing EC2 instance | inbound rules of NACL |
↓ | EC2 Instance Security Group | inbound rules of SG |
↓ | EC2 Instance Elastic Network Interface | — |
Destination | EC2 Instance | — |
dc-arch-2023.customer.ALTERNATE.10-8.v2.drawio
Resource | Filtering | Notes | |
---|---|---|---|
Source | TGW | — | |
↓ | TGW Attachment | — | |
↓ | TGW Attachment Elastic Network Interface | — | |
↓ | NACL of Subnet attached to TGW | outbound rules of NACL attached to utility subnet | The NACL bound to the utility subnets will allow all traffic in and out. |
↓ | Route Table of Subnet attached to TGW | — | |
↓ | NACL of Subnet containing EC2 instance | inbound rules of NACL for destination subnet | |
↓ | EC2 Instance Security Group | inbound rules of SG | |
Destination | EC2 Instance Elastic Network Interface | — |
Before the migration is executed, a set of resources in Cornell AWS accounts will be tagged with details about the migration. In addition, a small set of new resources that support the v2 architecture will be created in Cornell AWS accounts. After the migration is complete, a few resources not used in the v1 architecture will be deleted.
Cornell AWS customers will have the opportunity to provide feedback before migration and any resource deletion that affects their AWS accounts.
For this migration, we are tagging AWS resources to provide information about how the each resource is involved in the migration itself, the v1 architecture, and the v2 architecture.
Tag Key | Tag Values | Description | VPC | Subnets | Route Tables | NACLs ‡ | Transit Gateway | Virtual Private | Direct Connect Virtual Interfaces |
---|---|---|---|---|---|---|---|---|---|
cit:dc-arch-migration-target | yes/no | Will this resource itself be affected as part of the migration? | |||||||
cit:dc-arch-migration-description | prose | Description of planned changes to this resource | |||||||
cit:dc-arch-version | v1/v2 | Is this a v1 or v2 architecture resource? After migration, v1 resources utilized in the v2 architecture will be relabeled as v2 resources. | |||||||
cit:dc-arch-migration-new-resource | yes/no | Is this a new resource specifically created for the v2 architecture? | n/a | n/a | n/a | n/a | |||
cit:dc-arch-migration-replaces | resource ID | If this v2 resource will be replacing a v1 resource, this ID references the resource that will be replaced. | n/a | n/a | n/a | n/a | n/a | n/a | |
cit:subnet-type | public/private/utility | Is this a private or public subnet? Public subnets are those with a route to an Internet Gateway. Utility subnets will be created specifically to use for TGW Attachments. Private subnets are all subnets that are not public and are not utility subnets. | n/a | n/a | n/a | n/a | n/a | n/a | |
cit:tgw-attachment-target | yes/no | Will a Transit Gateway be attached to this subnet? | n/a | n/a | n/a | n/a | n/a | n/a | |
cit:dc-arch-exclude-tgw-routes | yes/no | This tag is applied only to the new Route Table that is created for use by the TGW Attachment utility subnets | n/a | n/a | n/a | n/a | n/a | n/a | |
cit:dc-vgw | yes/no | Does this Route Table contain rules referencing a VGW? | n/a | n/a | n/a | n/a | n/a | n/a | |
Cost Center | R524755 | This tag added to TGW Attachments will result in CIT paying for the $0.05/hr cost of attaching a VPC to a TGW. | n/a | n/a | n/a | n/a | n/a | n/a |
‡ Only the NACL created for use by utility subnets will be tagged.
Direct Connect Gateways are also involved in the migration but cannot be tagged.
A few new resources will be created as part of this migration.
If you use Terraform or other infrastructure-as-code tools to manage your VPC, let us know. We can work directly with you to allow your tools to create or import these new resources.
New AWS resource groups collect references to relevant AWS account resources in one place (per Cornell AWS account) for easy reference and review:
Resources can and will appear in multiple resource groups!
These Resource Groups will be created during the Preparation phase of the migration. See Migration Process.
If you use Terraform or other infrastructure-as-code tools to manage your VPC, you may need to add configuration to instruct those tools to ignore these new tags. For example, we have specific guidance for Terraform: Terraform Configuration Guidance for 2023 Direct Connect Architecture Migration.
Some resources that belong in these Resource Groups will not be present because of limitations in the the resource types that Resource Groups can handle. These resource types are:
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The AWS Transit Gateways used in the v2 architecture require different routing rules than the Virtual Private Gateways (VGW) used in the v1 architecture. Each VPC Route Table that references a Virtual Private Gateway will be duplicated and, in the new Route Table, rules referencing a VGW will be replaced with rules referencing a TGW Attachment. The new Route Tables will not include "blackhole" routes (i.e. routes to resources, like old peering connections, that no longer exist) from the original Route Tables.
These new Route Tables will be created prior to the migration, but will not actually be utilized until the migration is executed. When migration is executed, subnets associated with the v1 Route Tables will be re-associated to the corresponding v2 Route Tables. Similarly, if the "main" Route Table for the VPC references a VGW, the corresponding v2 Route Table will be set as the "main" Route Table for the VPC.
These Route Tables will be created during the Migration phase of the migration. See Migration Process.
New "utility" subnets will be created in each VPC. The sole purpose for these subnets is to be used to make TGW Attachments. One new subnet will be created for each AZ where the VPC has private or public subnets. (This provides the best resiliency for the Direct Connect connectivity through the TGW.)
In order to create these subnets, VPCs will have an additional CIDR block associated with it. The new subnets will be created with /28 CIDR blocks from the new CIDR attached to the VPC. These tiny subnets (~16 IPv4 addresses) should not be used for anything else. The Route Tables and NACLs associated with these subnets make them unsuitable for general use.
The Network ACLs already in customer VPCs will not be affected by this migration. However, a new NACL will be created in each VPC and associated with the new utility subnets. The NACL will be permissive (allowing all traffic in and out) and named in such a way to discourage use for other purposes.
Transit Gateway Attachments are the mechanism that VPCs connect to Transit Gateways. The Transit Gateways we use in the v2 architecture reside in a central AWS account, and a TGW Attachment is what links the VPC in a Cornell AWS account to those central TGWs.
Unlike Virtual Private Gateways, TGW Attachments connect to specific subnets in a VPC. We will be making these TGW Attachments to the utility subnets in VPCs which were specifically created for this purpose.
TGW Attachments will be created during the Migration phase of the migration. See Migration Process.
After migration is complete, a few resources will be deleted during the Cleanup phase of the migration. These are:
Neither VGWs nor DCVIFs have a role in the v2 architecture.
V1 Route Tables will not be deleted, but will not be used in the v2 architecture. Cornell AWS account owners can delete the v1 Route Tables if they wish. Once the VGWs are deleted, those v1 Route Tables will not be all that functional. |
The management and routing simplification offered by the v2 architecture comes with a shift in costs seen by Cornell AWS accounts using Direct Connect, but the overall impact to Cornell AWS account costs should be negligible.
Cornell AWS accounts using Direct Connect saw these Direct Connect-related charges:
These charges are involved in the v2 architecture:
In total, Cornell AWS accounts using Direct Connect should not experience any significant change in charges for using the v2 Direct Connect architecture. The one new cost that customers will see on invoices is being paid by CIT through the use of a Cost Center tag on the relevant resources.
draw.io source: direct-connect-migration-process.v2.drawio
Phase | Stage | Timeframe | Status | Activity | Impact on Cornell AWS Account VPC Networks |
---|---|---|---|---|---|
Preparation | Data Collection | November 2022 |
| none | |
Resource Tagging |
|
| none | ||
Resource Groups |
| none | |||
Customer Input #1 | - |
| none | ||
Migration | Transit Gateway Attachments | - |
| none | |
Customer Input #2 | - |
| none | ||
v2 BGP Updated | 7am |
| Azure-to-AWS-VPC traffic may begin to use the v2 architecture (in just the one direction). This is limited only to Azure-to-AWS-VPC traffic due to Cornell's network architecture. | ||
VPC Routing Updated | 9am |
|
| ||
Campus Direct Connect Routes Updated | 9am |
|
| ||
Cleanup | Customer Account Cleanup | - |
| none | |
Campus Direct Connect Cleanup |
| none |
Customers have the option to request that migration for their VPC(s) occur during the week of Jan 9-13 instead of the default migration dates of January 17 and 18. This is especially encouraged for customers that have a separate sandbox or development VPC that needs to be migrated. We can also support taking both migration steps on the same alternate day, but we'd like to leave a 1-4 hour gap between migration steps to confirm that the "VPC Routing Updated" step was successful before continuing to the "Campus Direct Connect Routes Updates" step.
Both the "VPC Routing Updated" and the "Campus Direct Connect Routes Updated" steps have simple rollback mechanism. If you discover problems with networking in your VPC after either step and think the change needs to be rolled back, send an email to cloud-incident@cornell.edu and ping Paul Allen (pea1) on Teams.
The list of AWS accounts affected by this migration is here: Cornell AWS Accounts Affected by 2023 Direct Connect Architecture Migration
You will receive multiple emails to the email address associated with the root user of your Cornell AWS account. These emails will make announcements and ask for your input during the migration process.
As of , our testing indicates that we should be able to complete this migration without any interruption in overall Direct Connect connectivity. However we cannot guarantee this for individual VPCs. If interruptions occur, they should be brief (minutes, not hours).
Cornell AWS accounts will not experience substantive differences in charges between v1 and v2 architecture. A new $36/mo charge for each VPC connected to the v2 architecture is billed directly to a CIT KFS account.
For more details, please see the Costs section above.
VPC peering is not affected by this change.
Since the Transit Gateway in the v2 architecture is configured to fully interconnect attached VPCs, most VPC peering among Cornell AWS VPCs could be removed eventually. When VPC peering is removed, VPC-to-VPC traffic that formerly used a peering connection would use the Transit Gateway instead. All traffic would remain in AWS, and the traffic would take two (2) hops to reach the target VPC instead of the one (1) hop that the peering connections support. There are two cases where VPC peering would need to remain in place:
Reducing the amount of peering amongst Cornell AWS VPCs will take place later and customers will be contacted separately about that. No peering changes are planned as part of the Direct Connect architecture migration. |
Our goal with this migration is that the routing of traffic between your VPC and Cornell public and private CIDR blocks will remain effectively unchanged between the v1 and v2 architectures. I.e. the Direct Connect routing option that you chose when your Direct Connect connectivity was established will remain in place. Those routing options are "private network extension", "hybrid", and "all campus" routing. For details on those options see Cornell AWS Direct Connect Routing Diagrams.
The exact pathways that Direct Connect traffic takes will change between the v1 and v2 architectures. But, the starting point (e.g., your VPC) and endpoint (e.g. a campus VLAN) of this traffic will constant.
See detailed schedule above.
Yes. See Alternate Migration Days above.
Yes. Each of the two active migration steps ("VPC Routing Updated" and "Campus Direct Connect Routes Updated") can be individually rolled back for each migrating AWS VPC. See Rollback above.
If you use Terraform or a similar tool to manage your VPCs, please inform the Cloud Team during the Customer Input #1 stage. You would have several options to update your infrastructure-as-code configuration to support this migration. You could import the new Route Tables and TGW Attachments, or you could create your own Route Tables and TGW Attachments.
During the Preparation phase, you can tell Terraform to ignore the "cit:" tags that have been added to your network resources. This guide shows how: Terraform Configuration Guidance for 2023 Direct Connect Architecture Migration.
Yes, you can. Just contact cloud-support@cornell.edu. Depending on the timing of things, we may need to migrate your Direct Connect connectivity to the v2 architecture before removing Direct Connect from your account entirely.