Internet Protocol (IP) is the standard that lets computers on different networks send data to each other. It breaks data into packets, labels each one with a source and destination address, and lets routers pass the packets from network to network until they reach the right device. Almost every modern network service, from internet access and cloud applications to phone calls and security cameras, runs over IP.
At a glance
- IP gives every device on a network an address and defines how packets carrying data are labeled and forwarded.
- Routers forward each packet independently, choosing the next hop from their routing tables.
- Delivery is best effort: IP does not promise that packets arrive, or arrive in order. Protocols above it, such as TCP, add that.
- Two versions are in use: IPv4, whose addresses have run out, and IPv6, with a vastly larger address space.
- “IP-based” services, such as VoIP and SIP trunking, share one network instead of needing separate circuits.
What problem it solves
Before IP, networks built by different organizations and vendors used their own addressing and rules, and connecting them was difficult. IP provided one common layer that any network could adopt. Whatever the physical link underneath, whether fiber, copper, Wi-Fi or cellular, and whatever the application on top, packets can move between networks as long as both ends speak IP.
For businesses, that common layer is why voice, video, data and building systems can now run over the same connections. Services that once needed dedicated lines, such as phone service over copper or private data circuits, have largely moved to IP. That lowers cost and simplifies management, but it also means one network’s performance and security affect everything on it.
How it works
Packets and headers. Data is split into packets. Each packet carries a header with the source and destination IP addresses, a counter that limits how many routers it can pass through, the protocol of the data inside (such as TCP or UDP), and a field that can mark its priority.
Addresses and prefixes. An IP address identifies a device’s network connection. Addresses are grouped into prefixes, such as a /24 in IPv4, that describe a network. Routers work with prefixes, not individual addresses, which is what lets the internet’s routing tables stay manageable.
Routing. Each router looks at a packet’s destination, finds the most specific matching prefix in its routing table, and forwards the packet toward the next router. Routes are configured statically or learned through routing protocols: OSPF or similar protocols inside one organization’s network, and Border Gateway Protocol (BGP) between networks on the internet.
Best-effort delivery. If a link is congested, routers drop packets. TCP detects missing data and resends it; UDP does not, so real-time applications using UDP rely on enough capacity and on Quality of Service (QoS) handling. Diagnostic tools such as ping and traceroute use ICMP, a companion protocol to IP.
Private addressing and NAT. Because IPv4 addresses are scarce, most internal networks use private address ranges and Network Address Translation (NAT) to share a few public addresses. IPv6 removes the shortage but is adopted unevenly, so many networks run both versions.
For help planning address space and moving to IPv6, see our IPv4/IPv6 Addresses solution page.
When it matters for buyers
- Comparing network quotes. Terms like IP transit, IP transport, IP VPN and IP voice all build on IP but buy different things; check what each one includes.
- Moving voice and video to IP. Calls are sensitive to delay, jitter and loss, so QoS and capacity matter more than headline bandwidth.
- Address planning. Mergers, new sites and cloud networks can bring overlapping private ranges that are painful to fix later.
- IPv6 readiness. Customers, partners or government contracts may require IPv6 support, and some providers charge for additional IPv4 addresses.
- Security. Every IP-connected device, including cameras and building systems, is reachable on the network and needs to be segmented and patched.
Questions to ask vendors
- Is the service delivered natively over IP, and does it support both IPv4 and IPv6?
- How many public IPv4 addresses are included, and what do additional addresses cost?
- How do you handle QoS markings on our traffic, and are they honored across your network?
- What latency, jitter and packet-loss commitments apply to IP traffic in your SLA?
- Will we be behind your NAT (carrier-grade NAT), or will we get our own public addresses?
- Can we bring our own IP addresses, and do you support BGP?
How it differs from IPv4 and IPv6 Addresses
IP is the protocol: the rules for addressing, packaging and forwarding data. IPv4 and IPv6 addresses are the identifiers that protocol uses, in its two current versions. Questions about how traffic moves belong to IP; questions about getting, planning and running out of addresses belong to addressing.
Problems this helps with
- Not sure what "IP-based" means on a provider's quote
- Calls and video break up even though the internet seems fine
- Running out of IP addresses or juggling conflicting address ranges
