# Networking

Linking compute resources and providing access to applications is the key function of Azure networking. Networking functionality in Azure includes a range of options to connect the outside world to services and features in the global Azure datacenters.

| Service name                   | Service function                                                                      |
| ------------------------------ | ------------------------------------------------------------------------------------- |
| Azure Virtual Network          | Connects VMs to incoming virtual private network (VPN) connections.                   |
| Azure Load Balancer            | Balances inbound and outbound connections to applications or service endpoints.       |
| Azure Application Gateway      | Optimizes app server farm delivery while increasing application security.             |
| Azure VPN Gateway              | Accesses Azure Virtual Networks through high-performance VPN gateways.                |
| Azure DNS                      | Provides ultra-fast DNS responses and ultra-high domain availability.                 |
| Azure Content Delivery Network | Delivers high-bandwidth content to customers globally.                                |
| Azure DDoS Protection          | Protects Azure-hosted applications from distributed denial of service (DDOS) attacks. |
| Azure Traffic Manager          | Distributes network traffic across Azure regions worldwide.                           |
| Azure ExpressRoute             | Connects to Azure over high-bandwidth dedicated secure connections.                   |
| Azure Network Watcher          | Monitors and diagnoses network issues by using scenario-based analysis.               |
| Azure Firewall                 | Implements high-security, high-availability firewall with unlimited scalability.      |
| Azure Virtual WAN              | Creates a unified wide area network (WAN) that connects local and remote sites.       |

## Azure Virtual Network

* enables Azure resources to communicate with
  * each other,
  * users on the internet,
  * on-premises client computers.

Virtual Network peering allows linking virtual networks which can be in separate regions thereby creating a global interconnected network.

UDR is user-defined routing that allows network admins to control the routing tables between subnets within a VNet, as well as between VNets

## Azure VPN Gateway

* a type of virtual network gateway
* Azure VPN gateway instances are deployed in Azure Virtual Network instances and enables:
  * Site-to-Site: connect on-premises datacenters to virtual networks
  * Point-to-Site: connect individual devices to virtual networks
  * Network-to-Network: connect virtual networks to other virtual networks

| Policy-based VPNs | Route-based VPNs |
| ----------------- | ---------------- |
|                   |                  |

## Azure ExpressRoute

* Layer 3 connectivity between your on-premises network and the Microsoft Cloud through a connectivity provider.
  * connectivity can be from
    * any-to-any (IPVPN) network,
    * point-to-point Ethernet connection&#x20;
    * virtual cross-connection via an Ethernet Exchange.
* establish connection to Microsoft cloud services such as Azure and Microsoft 365.
* dynamic routing between your network and Microsoft via BGP
* offers
  * reliability
  * faster speed
  * consistent latencies&#x20;
  * high security

## Azure Firewall

[Azure Firewall](https://azure.microsoft.com/services/azure-firewall) is a managed, cloud-based network security service that helps protect resources in your Azure virtual networks.

&#x20;Azure Firewall is a _stateful_ firewall. A stateful firewall analyzes the complete context of a network connection, not just an individual packet of network traffic.&#x20;

[Azure Application Gateway](https://azure.microsoft.com/services/application-gateway) also provides a firewall that's called the _web application firewall_ (WAF). WAF provides centralized, inbound protection for your web applications against common exploits and vulnerabilities. [Azure Front Door](https://azure.microsoft.com/services/frontdoor/) and [Azure Content Delivery Network](https://azure.microsoft.com/services/cdn/) also provide WAF services.\


&#x20;A [network security group](https://docs.microsoft.com/en-us/azure/virtual-network/security-overview#network-security-groups?azure-portal=true) enables you to filter network traffic to and from Azure resources within an Azure virtual network.
