Ad server vs DSP: what each does and where Epom fits
How an ad server and a DSP differ, why they are complementary, and how Epom's ad server auctions your direct campaigns against the DSP partners you plug in.
“Ad server” and “DSP” get used as if they were rival products you have to choose between. They are not — they do different jobs, and Epom uses both at once. Epom is an ad server, and a DSP is a bidder you plug into it. This page explains the split in plain terms and shows exactly where each one sits in Epom, so you can answer the real question: do I need to add a DSP, or is Epom already enough?
The short version
- An ad server stores your inventory and creatives, decides which ad wins each request, and logs the result. It is the referee and the record-keeper. Epom is the ad server.
- A DSP (demand-side platform) is a buyer’s tool. It shops for impressions across many supply sources and bids on the ones it wants, in real time. In Epom, a DSP is an external partner whose bids compete inside the same auction Epom already runs.
You always have an ad server (Epom). A DSP is optional extra demand you connect to it.
What the ad server does — Epom’s job
When a page, app or player requests an ad, Epom’s ad server runs one fixed pipeline (how ad selection works):
- Resolves the placement and gathers the demand linked to it.
- Filters that demand by pre-targeting, targeting, capping, limits and format fit.
- Ranks and picks a winner by priority tier, then campaign, then banner.
- Generates the markup, substitutes macros, attaches tracking, and returns it.
- Logs the impression, click and conversion so it shows up in Analytics.
Everything you build in the account area — advertisers, campaigns, banners, sites, zones, placements — is demand and supply that this ad server owns and serves directly. That is the whole quick-start walkthrough: no DSP involved.
What a DSP does — the buyer’s side
A DSP works for advertisers, not publishers. Its job is to buy impressions programmatically: it receives bid requests describing an impression (the user, the site, the format), decides how much that impression is worth to its advertisers, and returns a bid with a price and a creative. It never stores your inventory or runs your auction — it just answers “here’s my price for this one impression.”
In Epom you don’t operate a DSP; you connect to one as an OpenRTB demand partner (your network administrator configures it under DSP partners). The pre-built partner types Epom ships (TrafficStars, ExoClick, Kadam, TwinRed and others) plus the plain-OpenRTB Custom DSP Endpoint type are all examples of this: external bidders you invite into your auction.
Note: the mirror-image term is SSP (supply-side platform) — the seller’s programmatic tool. When Epom sends a bid request to a DSP partner, Epom is acting as the SSP for that exchange. You don’t configure a separate SSP; the ad server plays that role.
Where they meet: two demand sources, one auction
The point that makes Epom coherent is that direct campaigns and DSP partners are both just demand to the same ad server. When the pipeline picks a winner, a programmatic banner is not a finished creative — it is a placeholder for an auction:
- If the pick lands on a direct banner, Epom serves your stored creative.
- If the pick lands on an OpenRTB (DSP) banner, Epom fires bid requests to the eligible DSP partners, collects their bids, drops any creative that creative scanning has blocked, and serves the winning bid’s creative. The winner pays its own bid (first price) unless a second-price setting applies, and a bid below the bid floor never wins — see first vs second price.
- If no acceptable bid comes back, Epom excludes the programmatic banners and re-runs the pick over the remaining direct demand in the same priority tier, then the tiers below it — so a dead auction still fills with your own ads when it can.
So your direct sales and your DSP demand compete for the same impression under the same rules (priority, targeting, floors). The ad server is the single referee; the DSP is one more bidder at the table.
”Do I need both?”
| Your situation | What you need |
|---|---|
| You sell your own inventory to your own/direct advertisers | The ad server (Epom) alone. Build advertisers, campaigns, banners; link and serve. |
| You have unsold inventory and want programmatic demand to fill it | The ad server plus one or more DSP partners connected via OpenRTB. |
| You want direct deals to take priority and programmatic to backfill | Both — put direct campaigns in a higher priority tier than the OpenRTB banners. |
| You are a pure buyer with no inventory | A DSP is the buyer’s tool; Epom’s ad server is a seller/network platform. Different job. |
The common case for an Epom network is both at once: your direct campaigns carry the premium demand and DSP partners monetise whatever direct demand doesn’t fill — all decided in the one auction.
Corner cases
Corner case: priority still beats price across the boundary. A high-priority direct campaign outserves a DSP bid even when the DSP would pay more, because eCPM ranking runs only inside one priority tier. If you want your direct floor price to genuinely compete with programmatic, put the direct campaign and the OpenRTB banners in the same tier.
Corner case: the banner’s own Pricing card offers CPM alone for an OpenRTB banner, whatever your CPC/CPA permissions — what it earns is the auction price, not a price list you type in. The event a partner pays on (CPM, CPC or CPI) is a separate setting on the DSP partner. See OpenRTB DSP banners.
Corner case: connecting a DSP is a network administrator’s action, not a demand-user one. Advertisers and network managers pick from the partners that already exist; they can’t add a bidder themselves. The network administrator works in Admin → Demand partners (DSP) → DSP partners, or hands the same screens to network staff through the account’s RTB tab (three RTB Management permissions, all shipped disabled). If a partner you expect is missing from the banner’s DSP list, it either hasn’t been configured there or has been deactivated — a deactivated partner is not offered.
