UDP

In the Ultra Transcenders books

AZ-305AZ-7002V0-17.25AZ-900SC-900SC-200SC-300AZ-802MD-102

Each book explains UDP in context, with comparison tables and the common traps.

Terms in this definition

• Connection

  Resource that attaches a virtual network gateway to its peer, which may be an ExpressRoute circuit, a second VNet gateway (Vnet2Vnet) or a local network gateway over IPsec. Resetting it recovers a single tunnel and avoids rebooting the whole gateway.

Related terms

• AH

  Short for Authentication Header, an IPsec protocol that verifies the sender and integrity of an entire IP packet but leaves it unencrypted. Network security group rules can filter on it, as they can on TCP, UDP, ICMP and ESP.

• HA Ports

  A rule on an internal Standard Load Balancer, using protocol All and port 0, that balances every TCP and UDP flow on every port, which suits active-active NVAs.

• ICMP

  The protocol behind ping, distinct from both UDP and TCP. Between peered VNets, the default AllowVnetInBound NSG rule permits it.

• L4

  In the OSI model, layer 4 is where TCP and UDP ports live, also called the transport layer. Network rules in Azure Firewall, and the mitigations in DDoS Protection, both act at layers 3 and 4.

• Network Watcher IP flow verify

  Checks a 5-tuple against the security and admin rules on a VM's NIC and reports whether it is allowed or denied, naming the rule responsible. Only TCP and UDP are supported, and scale sets are excluded.

• NTP

  The Network Time Protocol, on UDP port 123, which the Windows Time service relies on. Domain members take time from the domain hierarchy, which leads up to the PDC emulator in the forest root, and that server should sync with an outside source.

• SMB over QUIC

  Carries SMB inside QUIC, using UDP port 443 and TLS 1.3, so people can reach file shares safely with no VPN. Every edition of Windows Server 2025 includes it, as does Windows Server 2022 Datacenter: Azure Edition.

• STUN

  The technique RDP Shortpath for Windows 365 uses to find public addresses so a client and Cloud PC can open a direct UDP link.