DSPs and SSPs in CTV advertising: how programmatic trading works

What is a DSP?

A demand-side platform (DSP) is software that allows advertisers and agencies to buy digital ad inventory programmatically — across multiple publishers, exchanges, and platforms — from a single interface. Instead of negotiating with each publisher separately, a buyer uses a DSP to set targeting criteria, bid prices, budgets, and creative, then let the platform execute millions of individual impression-level decisions in real time.

The DSP connects to supply-side platforms (SSPs) and ad exchanges via real-time bidding (RTB) protocols. When a publisher signals that an impression is available, the DSP evaluates it within milliseconds and decides whether to bid, and at what price.

What a DSP does for a CTV buyer

• Audience targeting: Match the available impression against the advertiser's target audience — demographics, location, device type, content category, behavioural segments.
• Bid decisioning: Calculate the right bid price based on campaign objectives (reach, frequency, VCR, conversion), available budget, and the competitive auction environment.
• Frequency management: Track how many times a given device has seen the ad and cap exposures to avoid overserving.
• Creative trafficking: Store and serve the video creative to the publisher's ad server when the DSP wins an auction.
• Measurement and reporting: Record impressions, video completion events, reach, and frequency across the campaign.

Major DSPs used for India CTV

• Google DV360 (Display & Video 360): The most widely used DSP in India. Primary route for YouTube CTV buying and Google Ad Manager inventory. Most large agency holding groups run DV360 as their primary programmatic platform.
• The Trade Desk: Growing India presence, strong for open programmatic CTV, preferred by buyers who want independence from Google's stack. The Trade Desk also has integrations with some India-specific SSPs.
• Amazon DSP: The exclusive route to Fire TV and Amazon Prime Video programmatic inventory. Amazon's identity graph (purchase data, Prime membership) makes it uniquely valuable for performance-oriented CTV campaigns in India.
• Xandr (Microsoft): Used by some India agency groups for cross-market CTV buys, particularly for advertisers running global campaigns.
• InMobi mDSP: India-built DSP with strong mobile roots and growing CTV capabilities. Better coverage of mid-tier India CTV and OTT inventory than global DSPs.

What is an SSP?

A supply-side platform (SSP) is software used by publishers to manage, package, and sell their ad inventory programmatically. The SSP is the publisher's counterpart to the buyer's DSP. It receives bid requests from connected DSPs, runs the auction, selects the winning bid, and passes the result to the publisher's ad server for delivery.

An SSP allows a publisher to expose their inventory to many buyers simultaneously, maximise yield across the available demand, and enforce controls like floor prices, buyer allowlists, and brand safety rules.

What an SSP does for a CTV publisher

• Demand aggregation: Connect to dozens of DSPs simultaneously so many buyers compete for each impression, driving up effective CPMs.
• Auction management: Run the auction — collect bids, enforce the floor price, select the winner.
• Deal management: Manage private marketplace (PMP) deals and programmatic guaranteed (PG) deals with specific buyers at negotiated prices.
• Inventory controls: Let publishers set floor prices, block certain buyer categories, enforce brand safety standards.
• Yield reporting: Report fill rates, average CPMs, demand source performance so publishers can optimise their monetisation setup.

Major SSPs used in India CTV

• Google Ad Manager (GAM): Functions as both the dominant publisher ad server and a de facto SSP for many India CTV publishers. GAM connects directly to DV360 demand through Google's unified auction, giving it structural advantages in inventory access.
• Magnite: The largest independent CTV-focused SSP globally. Has integrations with several India CTV publishers and growing presence as the India CTV programmatic market develops.
• PubMatic: India-headquartered SSP with strong local relationships. Active in India CTV and OTT programmatic, particularly for mid-tier publishers.
• FreeWheel (Comcast): Specialised in video and CTV ad serving and supply management. Used by some premium video publishers for its video-native capabilities.
• SpotX (now part of Magnite): CTV-specialist SSP absorbed into Magnite; its technology stack continues to power CTV supply management for several publishers.

How DSP and SSP interact: the real-time bidding flow

The interaction between DSP and SSP is what makes programmatic CTV possible. Here is the sequence:

1. Impression available: A viewer is about to see an ad break on a CTV app. The publisher's ad server signals the SSP that an impression is available.
2. Bid request broadcast: The SSP packages the impression as a bid request — including device type, content context, location, audience signals, floor price, and any deal IDs — and sends it to connected DSPs simultaneously.
3. DSP evaluation: Each DSP evaluates the bid request against active campaigns. Does any campaign target this impression type? What is the right bid? Does frequency capping apply? The DSP responds with a bid (or a no-bid if no campaign matches).
4. Auction resolution: The SSP collects all bids, identifies the highest bid above the floor price, and returns the winner to the publisher's ad server. In first-price auctions (now standard), the winner pays their actual bid. In second-price auctions, they pay the second-highest bid plus one cent.
5. Ad delivery: The publisher's ad server retrieves the winning creative from the DSP and delivers it to the viewer — either through client-side insertion (the device fetches the ad) or server-side insertion (the ad is stitched into the stream at the server).
6. Impression tracking: VAST tracking pixels fire at impression start, quartile events, and completion. Both the DSP and the publisher's ad server record the impression independently.

The entire sequence — from impression signal to winning bid returned — completes in under 200 milliseconds.

Private marketplace (PMP) deals: how India CTV actually trades

Open RTB — where any DSP can bid on any available impression — is not how most premium India CTV inventory is sold. JioCinema, Hotstar, and Amazon Prime Video keep significant portions of their inventory in private environments:

• Private marketplace (PMP): The publisher creates a deal with specific buyers, giving them access to defined inventory at a negotiated floor price. Only buyers with the deal ID can participate in the auction for that inventory. PMPs combine the efficiency of programmatic with the control of direct sales.
• Programmatic guaranteed (PG): A direct deal executed programmatically. The buyer and publisher agree on volume, CPM, and targeting in advance. The DSP delivers to the agreed terms without an open auction. Used for premium placements like IPL pre-rolls where inventory is scarce and buyers want guaranteed access.
• Open auction: Remaining inventory after direct and PMP deals are fulfilled is available to any connected DSP. For India premium CTV publishers, the open auction inventory is often remnant — lower-priority placements or fill when direct pipelines are not at capacity.

For India CTV buyers, this means that programmatic access via DSP does not guarantee access to the best inventory. Premium IPL inventory on JioCinema, for example, requires a direct relationship and a PMP deal — not just a DV360 seat.

India-specific context: DSP and SSP market structure

India's CTV DSP/SSP landscape has several features that differ from the US or UK models:

• Google dominance: DV360 + Google Ad Manager form a dominant stack in India. Many publishers use GAM as their ad server and SSP simultaneously, and many buyers use DV360. This creates structural advantages for the Google supply path and can limit the transparency available to buyers using alternative DSPs.
• Limited open exchange: The premium India CTV publishers (JioCinema, Hotstar) do not fully open their inventory to open RTB. Buyers who want scale need PMP relationships, not just DSP access. The Trade Desk and other non-Google DSPs have fewer India CTV PMP connections than DV360.
• Walled garden asymmetry: YouTube CTV buying through DV360 is relatively open. Amazon CTV buying requires Amazon DSP. JioCinema and Hotstar buying is primarily direct or via specific agency programmatic arrangements. There is no single DSP that provides full India CTV coverage.
• SPO (supply path optimisation) is underdeveloped: In more mature CTV markets, buyers use supply path optimisation to identify the most direct, low-fee path from DSP to publisher. In India, the market is not yet sophisticated enough for most buyers to practise systematic SPO on CTV inventory.