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-# Waku's requirements on Codex
+# Waku's Requirements on Codex
 
-TODO
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+## Message Archival
+
+To be used for messages archival in Chat SDK, Qaku, opchan, etc.
+It assumes that a special user (admin, referred to as "original uploader") regularly bundles messages and pushes them to an external system.
+It then pushes the reference to the bundle over Waku.
+
+New users retrieve and listen to new messages using Waku upon start up.
+Then, they may retrieve bundles, likely because the know they are missing message via SDS.
+
+The original uploader is the one to determine how much persistence and guarantee they want for the bundle.
+It is application specific (eg until a Q&A is completed), and not related to users having downloaded the data. 
+
+Which means it's a scenario where:
+
+- Time from upload to retrieval is **not** critical (latest messages are available on Waku)
+- Several users can seed and download the bundle.
+
+This is very similar to BitTorrent integration in Status ([specs](https://github.com/vacp2p/rfc-index/blob/main/status/61/community-history-service.md))
+Some notes on BitTorrent integration in Status:
+
+1. Known issue is that the bundle is very large, and hence consumes a lot of bandwidth. I don't know if the bundle is "updated" or overridden.
+   On Waku app side, we need to be open to have one large bundle vs a series of manageable bundle. The latter offers more flexibility such as attaching bloom filters,
+   for selective download.
+2. The bundle download is indiscriminate, meaning every user will download it at some point, with SDS, we can do something smarter
+
+**Technical solutions**
+
+A comment on possible solutions:
+
+Also note (more of a personal opinion), usage of BitTorrent/webtorrent could be an acceptable starting point.
+
+Web is being solved by @vpavlin with vpavlin/qaku-cache which acts as a pinning gateway:
+
+> it is basically a pinning gateway, but instead of using HTTP to upload you use the Codex network itself.
+> It would be cool to add some auth - I was thinking about using Semaphore or RLN to limit who and how much can cache - WDYT?
+
+Or with a Codex web-client that can retrieve and upload from the network:
+
+> I think if we can get a Codex web-client which can upload to the network somehow, we are immediately
+> solving one of the biggest pain points of IPFS and have a great story for anyone "why are you building a new storage
+> and why should I use it?" - I definitely want this to happen:-)
+
+These are inferred in the FURPS below with requirements on web support and censorship-resistance.
+
+### Functionality
+
+1. Ability to transfer a bundle of 1MB or more between two or more nodes.
+2. Reference to bundle is 50kB or less.
+
+### Usability
+
+1. Developer can implement feature with 10 lines of code or less.
+
+### Reliability
+
+1. Download operation can be resumed.
+2. Upload operation can be resumed.
+3. As long as original uploader is online, bundle should be retrievable.
+4. As long as N out of M users are online, bundle should be retrievable.
+
+### Performance
+
+1. Time between bundle uploaded, and retrieved by users can be in the span of minutes and hours (we assumes messages are available in Waku store for several hours).
+2. The burden of re-upload is shared by users.
+
+### Supportability
+
+1. Library for Browser applications.
+2. Library for Nim desktop applications.
+3. Library for Nim mobile applications.
+4. Most users may be behind NAT routers and other domestic network setup.
+
+### + (Privacy, Anonymity, Censorship-Resistance, Deployments)
+
+1. The unavailability of a static host (IP, DNS) does not prevent a user to upload or download (censorship-resistance).
+2. A participant cannot determine original uploader's PII (anonymity).
+
+## Large File Transfer
+
+To be used when 2 users or more, are transferring a large payload. This may be a large image or video in a private chat.
+Or it could be a llm prompt that returns a large image or video.
+
+Due to the broadcast nature of Waku, it would hog too much bandwidth if every large file sent between users where sent over Waku.
+
+In terms of durability, it can be assumed that once all participants have downloaded the payload, it does not need to be retrievable anymore.
+It should also be assumed that the users may not be online at the same time (mobile).
+There is more expectation on timeliness of retrievability, as one would want to be able to download seconds after the upload happened.
+
+### Functionality
+
+1. Ability to transfer a payload of 1MB or more between two or more peers.
+2. Reference to payload is less than 50kB.
+
+### Usability
+
+1. Developer can implement feature with 10 lines of code or less.
+
+### Reliability
+
+1. Download operation can be resumed.
+2. Upload operation can be resumed.
+3. Payload should be retrievable even if original uploader goes offline.
+4. Once all recipients have downloaded the payload, there is no more expectations on being able to retrieve the payload.
+
+### Performance
+
+1. Payload download should start within seconds of the upload start.
+
+### Supportability
+
+1. Library for Browser applications.
+2. Library for Nim desktop applications.
+3. Library for Nim mobile applications.
+4. Most users may be behind NAT routers and other domestic network setup.
+
+### + (Privacy, Anonymity, Censorship-Resistance, Deployments)
+
+1. The unavailability of a static host (IP, DNS) does not prevent a user to upload or download (censorship-resistance).
+2. An external observer cannot tie the PIIs of the uploader and downloaders of one payload;
+   it is assumed that the reference to the payload (eg, CID) is not leaked outside the participants.
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