IP Transit vs CDN
IP transit buys full internet reachability over BGP, while a CDN moves content closer to users. We compare the cost model, reach and control of each.
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IP transit is a paid service in which a provider carries your BGP traffic to the entire internet. A CDN (content delivery network) is a distributed infrastructure of cache servers that copies and serves content closer to the end user. They are not interchangeable. Transit gives universal reachability for all of your network's traffic, while a CDN offloads only repeatable HTTP content and media. An operator usually runs both, because they solve different problems.
| Aspect | IP transit | CDN |
|---|---|---|
| What you buy | Reachability of the entire internet | Delivery of your content closer to the user |
| Traffic direction | Outbound and inbound | Mostly outbound, served from cache |
| Billing | By bandwidth: 95th percentile or commit | By data transferred and request count |
| Routing control | Full, your own BGP sessions | Limited, held by the provider |
| Effect on latency | Depends on the path to the destination | Lower thanks to edge nodes |
| Substitutable | Does not replace a CDN | Does not replace transit |
| Typical buyer | Operator, hosting provider, enterprise | A service with heavy content volume |
Cost model
IP transit is billed for capacity, most often on a 95th-percentile basis in Mbps or as a flat fee for a port of a given size in Gbps, regardless of whether the traffic is video, gaming or email. A CDN shifts the cost from capacity to volume delivered (usually per GB or TB), often with pricing that varies by geographic region. The difference matters: with transit you pay for every bit leaving your network, while a CDN lowers your transit bill because cache nodes answer requests instead of your upstream link.
- IP transit: capacity fee, usually 95th percentile in Mbps or flat per-port in Gbps.
- CDN: fee for volume delivered (GB/TB) and request count, often priced per region.
- A CDN reduces transit cost by serving repeatable traffic from cache (cache hits).
- Transit covers all network traffic; a CDN covers only cacheable content.
Reach and reachability
IP transit provides reachability to every prefix in the global BGP table. The provider advertises a default route or a full table and commits to deliver traffic to any destination. A CDN offers no such universality. It only accelerates delivery of content hosted on its edge nodes (PoPs), typically through anycast (described in RFC 4786 and RFC 7094) to steer users to the nearest node. Traffic that cannot be cached (BGP sessions, VoIP, customers' transit traffic, dynamic APIs) must still cross transit.
Control and routing
Transit gives you full control over BGP policy: you can influence routes with AS-path prepending, local-preference, MED and BGP communities, and run your own traffic engineering. A CDN moves that control to the delivery operator, who decides PoP placement, cache rules and user steering. You gain performance and resilience to traffic spikes, but lose some visibility and influence over the packet path. For latency-sensitive static content a CDN almost always wins, and for full control over reachability transit remains essential.
- Transit: full BGP control, namely local-preference, MED, AS-path prepending, communities.
- CDN: routing toward content is owned by the CDN operator and its anycast.
- A CDN adds resilience to traffic spikes and volumetric attacks at the content layer.
- Transit stays the base layer. Without it the network has no full internet reach.
IP transit and CDN on the AS202520 SkyPass network
AS202520 SkyPass delivers IP transit as the base layer of your reachability, with a full BGP table, redundancy and PoPs in Warsaw and Wrocław. Peering at Polish internet exchanges (THINX, TPIX, WRIX, 1-IX) shortens the path to local CDN nodes and content networks, so cached traffic reaches the user over a shorter route with lower latency. If you plan to offload content to a CDN, transit and peering from SkyPass form the foundation on which CDN edge nodes operate efficiently.
Frequently asked questions
Can a CDN replace IP transit?
No. A CDN only accelerates cacheable content and operates at the application layer. Transit provides reachability to the entire internet for every type of traffic, so the network still needs it as a base layer.
How does a CDN lower the transit bill?
CDN edge nodes answer repeatable requests from cache, so that traffic no longer loads your paid upstream link. The higher the cache hit ratio, the less traffic counted under the 95th-percentile model.
What role does anycast play in a CDN?
Anycast (RFC 4786, RFC 7094) lets the same address be advertised from many locations, so BGP steers a user to the nearest CDN node. This shortens the path and latency with no change on the client side.
Do I still need peering if I use a CDN?
Yes. Peering at a local IXP shortens the path between your network and CDN nodes and content networks, lowering latency and transit cost for the traffic that cache cannot serve.