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@ -5,13 +5,15 @@
<meta name="generator" content="Hugo 0.106.0">
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="WakuFilter is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of WakuRelay specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.
Content filtering # Protocol identifier*: /vac/waku/filter/2.0.0-beta1
Content filtering is a way to do message-based filtering. Currently the only content filter being applied is on contentTopic.">
<meta name="description" content="previous versions: 00
WakuFilter is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of WakuRelay specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.
Content filtering # Protocol identifiers:
filter-subscribe: /vac/waku/filter-subscribe/2.0.0-beta1 filter-push: /vac/waku/filter-push/2.0.0-beta1 Content filtering is a way to do message-based filtering. Currently the only content filter being applied is on contentTopic.">
<meta name="theme-color" content="#FFFFFF"><meta property="og:title" content="12/WAKU2-FILTER" />
<meta property="og:description" content="WakuFilter is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of WakuRelay specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.
Content filtering # Protocol identifier*: /vac/waku/filter/2.0.0-beta1
Content filtering is a way to do message-based filtering. Currently the only content filter being applied is on contentTopic." />
<meta property="og:description" content="previous versions: 00
WakuFilter is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of WakuRelay specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.
Content filtering # Protocol identifiers:
filter-subscribe: /vac/waku/filter-subscribe/2.0.0-beta1 filter-push: /vac/waku/filter-push/2.0.0-beta1 Content filtering is a way to do message-based filtering. Currently the only content filter being applied is on contentTopic." />
<meta property="og:type" content="article" />
<meta property="og:url" content="https://rfc.vac.dev/spec/12/" /><meta property="article:section" content="docs" />
@ -192,9 +194,18 @@ https://github.com/alex-shpak/hugo-book
</li>
<li><a href="#adversarial-model">Adversarial Model</a>
<ul>
<li><a href="#protobuf">Protobuf</a>
<li><a href="#protobuf">Protobuf</a></li>
<li><a href="#filter-subscribe">Filter-Subscribe</a>
<ul>
<li></li>
<li><a href="#filter-subscribe-request">Filter Subscribe Request</a></li>
<li><a href="#filter-subscribe-response">Filter Subscribe Response</a></li>
<li><a href="#filter-matching">Filter matching</a></li>
<li><a href="#filter-subscribe-types">Filter Subscribe Types</a></li>
</ul>
</li>
<li><a href="#filter-push">Filter-Push</a>
<ul>
<li><a href="#message-push">Message Push</a></li>
</ul>
</li>
</ul>
@ -267,12 +278,18 @@ https://github.com/alex-shpak/hugo-book
</li>
</ul><p><code>WakuFilter</code> is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of <code>WakuRelay</code> specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.</p>
</ul><p>previous versions: <a href="/spec/12/previous-versions/00/">00</a></p>
<hr>
<p><code>WakuFilter</code> is a protocol that enables subscribing to messages that a peer receives. This is a more lightweight version of <code>WakuRelay</code> specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire.</p>
<h1 id="content-filtering">
Content filtering
<a class="anchor" href="#content-filtering">#</a>
</h1>
<p><strong>Protocol identifier</strong>*: <code>/vac/waku/filter/2.0.0-beta1</code></p>
<p><strong>Protocol identifiers</strong>:</p>
<ul>
<li><em>filter-subscribe</em>: <code>/vac/waku/filter-subscribe/2.0.0-beta1</code></li>
<li><em>filter-push</em>: <code>/vac/waku/filter-push/2.0.0-beta1</code></li>
</ul>
<p>Content filtering is a way to do <a href="https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern#Message_filtering">message-based
filtering</a>.
Currently the only content filter being applied is on <code>contentTopic</code>. This
@ -321,71 +338,168 @@ frequent polling.</p>
Protobuf
<a class="anchor" href="#protobuf">#</a>
</h2>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-protobuf" data-lang="protobuf"><span style="display:flex;"><span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">FilterRequest</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">bool</span> subscribe <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">string</span> topic <span style="color:#f92672">=</span> <span style="color:#ae81ff">2</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">repeated</span> ContentFilter contentFilters <span style="color:#f92672">=</span> <span style="color:#ae81ff">3</span>;<span style="color:#960050;background-color:#1e0010">
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-protobuf" data-lang="protobuf"><span style="display:flex;"><span>syntax <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;proto3&#34;</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">message</span> <span style="color:#a6e22e">ContentFilter</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">string</span> contentTopic <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#75715e">// 12/WAKU2-FILTER rfc: https://rfc.vac.dev/spec/12/
</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span><span style="color:#f92672">package</span> waku<span style="color:#f92672">.</span>filter.v2;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#75715e">// Protocol identifier: /vac/waku/filter-subscribe/2.0.0-beta1
</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">FilterSubscribeRequest</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">enum</span> FilterSubscribeType {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> SUBSCRIBER_PING <span style="color:#f92672">=</span> <span style="color:#ae81ff">0</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> SUBSCRIBE <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> UNSUBSCRIBE <span style="color:#f92672">=</span> <span style="color:#ae81ff">2</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> UNSUBSCRIBE_ALL <span style="color:#f92672">=</span> <span style="color:#ae81ff">3</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> }<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">string</span> request_id <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> FilterSubscribeType filter_subscribe_type <span style="color:#f92672">=</span> <span style="color:#ae81ff">2</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#75715e">// Filter criteria
</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#66d9ef">optional</span> <span style="color:#66d9ef">string</span> pubsub_topic <span style="color:#f92672">=</span> <span style="color:#ae81ff">10</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">repeated</span> <span style="color:#66d9ef">string</span> content_topics <span style="color:#f92672">=</span> <span style="color:#ae81ff">11</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span>}<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">MessagePush</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">repeated</span> WakuMessage messages <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">FilterSubscribeResponse</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">string</span> request_id <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">uint32</span> status_code <span style="color:#f92672">=</span> <span style="color:#ae81ff">10</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">optional</span> <span style="color:#66d9ef">string</span> status_desc <span style="color:#f92672">=</span> <span style="color:#ae81ff">11</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span>}<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">FilterRPC</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">string</span> requestId <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> FilterRequest request <span style="color:#f92672">=</span> <span style="color:#ae81ff">2</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> MessagePush push <span style="color:#f92672">=</span> <span style="color:#ae81ff">3</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span><span style="color:#75715e">// Protocol identifier: /vac/waku/filter-push/2.0.0-beta1
</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span><span style="color:#66d9ef">message</span> <span style="color:#a6e22e">MessagePush</span> {<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> WakuMessage waku_message <span style="color:#f92672">=</span> <span style="color:#ae81ff">1</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span> <span style="color:#66d9ef">optional</span> <span style="color:#66d9ef">string</span> pubsub_topic <span style="color:#f92672">=</span> <span style="color:#ae81ff">2</span>;<span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span>}<span style="color:#960050;background-color:#1e0010">
</span></span></span></code></pre></div><h4 id="filterrpc">
FilterRPC
<a class="anchor" href="#filterrpc">#</a>
</span></span></span></code></pre></div><h2 id="filter-subscribe">
Filter-Subscribe
<a class="anchor" href="#filter-subscribe">#</a>
</h2>
<p>A filter service node MUST support the <em>filter-subscribe</em> protocol
to allow filter clients to subscribe, modify, refresh and unsubscribe a desired set of filter criteria.
The combination of different filter criteria for a specific filter client node is termed a &ldquo;subscription&rdquo;.
A filter client is interested in receiving messages matching the filter criteria in its registered subscriptions.</p>
<p>Since a filter service node is consuming resources to provide this service,
it MAY account for usage and adapt its service provision to certain clients.
An incentive mechanism is currently planned but underspecified.</p>
<h3 id="filter-subscribe-request">
Filter Subscribe Request
<a class="anchor" href="#filter-subscribe-request">#</a>
</h3>
<p>A client node MUST send all filter requests in a <code>FilterSubscribeRequest</code> message.
This request MUST contain a <code>request_id</code>.
The <code>request_id</code> MUST be a uniquely generated string.
Each request MUST include a <code>filter_subscribe_type</code>, indicating the type of request.</p>
<h3 id="filter-subscribe-response">
Filter Subscribe Response
<a class="anchor" href="#filter-subscribe-response">#</a>
</h3>
<p>In return to any <code>FilterSubscribeRequest</code>,
a filter service node SHOULD respond with a <code>FilterSubscribeResponse</code> with a <code>requestId</code> matching that of the request.
This response MUST contain a <code>status_code</code> indicating if the request was successful or not.
Successful status codes are in the <code>2xx</code> range.
Client nodes SHOULD consider all other status codes as error codes and assume that the requested operation had failed.
In addition, the filter service node MAY choose to provide a more detailed status description in the <code>status_desc</code> field.</p>
<h3 id="filter-matching">
Filter matching
<a class="anchor" href="#filter-matching">#</a>
</h3>
<p>In the description of each request type below,
the term &ldquo;filter criteria&rdquo; refers to the combination of <code>pubsub_topic</code> and a set of <code>content_topics</code>.
The request MAY include filter criteria, conditional to the selected <code>filter_subscribe_type</code>.
If the request contains filter criteria,
it MUST contain a <code>pubsub_topic</code>
and the <code>content_topics</code> set MUST NOT be empty.
A <code>WakuMessage</code> matches filter criteria when its <code>content_topic</code> is in the <code>content_topics</code> set
and it was published on a matching <code>pubsub_topic</code>.</p>
<h3 id="filter-subscribe-types">
Filter Subscribe Types
<a class="anchor" href="#filter-subscribe-types">#</a>
</h3>
<p>The following filter subscribe types are defined:</p>
<h4 id="subscriber_ping">
SUBSCRIBER_PING
<a class="anchor" href="#subscriber_ping">#</a>
</h4>
<p>A node MUST send all Filter messages (<code>FilterRequest</code>, <code>MessagePush</code>) wrapped inside a
<code>FilterRPC</code> this allows the node handler to determine how to handle a message as the Waku
Filter protocol is not a request response based protocol but instead a push based system.</p>
<p>The <code>requestId</code> MUST be a uniquely generated string. When a <code>MessagePush</code> is sent
the <code>requestId</code> MUST match the <code>requestId</code> of the subscribing <code>FilterRequest</code> whose filters
matched the message causing it to be pushed.</p>
<h4 id="filterrequest">
FilterRequest
<a class="anchor" href="#filterrequest">#</a>
<p>A filter client that sends a <code>FilterSubscribeRequest</code> with <code>filter_subscribe_type</code> set to <code>SUBSCRIBER_PING</code>
requests that the service node SHOULD indicate if it has any active subscriptions for this client.
The filter client SHOULD exclude any filter criteria from the request.
The filter service node SHOULD respond with a success code if it has any active subscriptions for this client
or an error code if not.
The filter service node SHOULD ignore any filter criteria in the request.</p>
<h4 id="subscribe">
SUBSCRIBE
<a class="anchor" href="#subscribe">#</a>
</h4>
<p>A <code>FilterRequest</code> contains an optional topic, zero or more content filters and
a boolean signifying whether to subscribe or unsubscribe to the given filters.
True signifies &lsquo;subscribe&rsquo; and false signifies &lsquo;unsubscribe&rsquo;.</p>
<p>A node that sends the RPC with a filter request and <code>subscribe</code> set to &rsquo;true&rsquo;
requests that the filter node SHOULD notify the light requesting node of messages
matching this filter.</p>
<p>A node that sends the RPC with a filter request and <code>subscribe</code> set to &lsquo;false&rsquo;
requests that the filter node SHOULD stop notifying the light requesting node
of messages matching this filter if it is currently doing so.</p>
<p>The filter matches when content filter and, optionally, a topic is matched.
Content filter is matched when a <code>WakuMessage</code> <code>contentTopic</code> field is the same.</p>
<p>A filter node SHOULD honor this request, though it MAY choose not to do so. If
it chooses not to do so it MAY tell the light why. The mechanism for doing this
is currently not specified. For notifying the light node a filter node sends a
MessagePush message.</p>
<p>Since such a filter node is doing extra work for a light node, it MAY also
account for usage and be selective in how much service it provides. This
mechanism is currently planned but underspecified.</p>
<h4 id="messagepush">
MessagePush
<a class="anchor" href="#messagepush">#</a>
<p>A filter client that sends a <code>FilterSubscribeRequest</code> with <code>filter_subscribe_type</code> set to <code>SUBSCRIBE</code>
requests that the service node SHOULD push messages matching this filter to the client.
The filter client MUST include the desired filter criteria in the request.
A client MAY use this request type to <em>modify</em> an existing subscription
by providing <em>additional</em> filter criteria in a new request.
A client MAY use this request type to <em>refresh</em> an existing subscription
by providing <em>the same</em> filter criteria in a new request.
The filter service node SHOULD respond with a success code if it successfully honored this request
or an error code if not.
The filter service node SHOULD respond with an error code and discard the request
if the subscribe request does not contain valid filter criteria,
i.e. both a <code>pubsub_topic</code> <em>and</em> a non-empty <code>content_topics</code> set.</p>
<h4 id="unsubscribe">
UNSUBSCRIBE
<a class="anchor" href="#unsubscribe">#</a>
</h4>
<p>A filter node that has received a filter request SHOULD push all messages that
match this filter to a light node. These <a href="./waku-message.md"><code>WakuMessage</code>&rsquo;s</a> are likely to come from the
<code>relay</code> protocol and be kept at the Node, but there MAY be other sources or
protocols where this comes from. This is up to the consumer of the protocol.</p>
<p>A filter node MUST NOT send a push message for messages that have not been
requested via a FilterRequest.</p>
<p>If a specific light node isn&rsquo;t connected to a filter node for some specific
period of time (e.g. a TTL), then the filter node MAY choose to not push these
messages to the node. This period is up to the consumer of the protocol and node
implementation, though a reasonable default is one minute.</p>
<p>A filter client that sends a <code>FilterSubscribeRequest</code> with <code>filter_subscribe_type</code> set to <code>UNSUBSCRIBE</code>
requests that the service node SHOULD <em>stop</em> pushing messages matching this filter to the client.
The filter client MUST include the filter criteria it desires to unsubscribe from in the request.
A client MAY use this request type to <em>modify</em> an existing subscription
by providing <em>a subset of</em> the original filter criteria to unsubscribe from in a new request.
The filter service node SHOULD respond with a success code if it successfully honored this request
or an error code if not.
The filter service node SHOULD respond with an error code and discard the request
if the unsubscribe request does not contain valid filter criteria,
i.e. both a <code>pubsub_topic</code> <em>and</em> a non-empty <code>content_topics</code> set.</p>
<h4 id="unsubscribe_all">
UNSUBSCRIBE_ALL
<a class="anchor" href="#unsubscribe_all">#</a>
</h4>
<p>A filter client that sends a <code>FilterSubscribeRequest</code> with <code>filter_subscribe_type</code> set to <code>UNSUBSCRIBE_ALL</code>
requests that the service node SHOULD <em>stop</em> pushing messages matching <em>any</em> filter to the client.
The filter client SHOULD exclude any filter criteria from the request.
The filter service node SHOULD remove any existing subscriptions for this client.
It SHOULD respond with a success code if it successfully honored this request
or an error code if not.</p>
<h2 id="filter-push">
Filter-Push
<a class="anchor" href="#filter-push">#</a>
</h2>
<p>A filter client node MUST support the <em>filter-push</em> protocol
to allow filter service nodes to push messages matching registered subscriptions to this client.</p>
<p>A filter service node SHOULD push all messages
matching the filter criteria in a registered subscription
to the subscribed filter client.
These <a href="./waku-message.md"><code>WakuMessage</code>s</a> are likely to come from <a href="https://rfc.vac.dev/spec/11/"><code>11/WAKU2-RELAY</code></a>,
but there MAY be other sources or protocols where this comes from.
This is up to the consumer of the protocol.</p>
<p>If a message push fails,
the filter service node MAY consider the client node to be unreachable.
If a specific filter client node is not reachable from the service node for a period of time,
the filter service node MAY choose to stop pushing messages to the client and remove its subscription.
This period is up to the service node implementation.
We consider <code>1 minute</code> to be a reasonable default.</p>
<h3 id="message-push">
Message Push
<a class="anchor" href="#message-push">#</a>
</h3>
<p>Each message MUST be pushed in a <code>MessagePush</code> message.
Each <code>MessagePush</code> MUST contain one (and only one) <code>waku_message</code>.
If this message was received on a specific <code>pubsub_topic</code>,
it SHOULD be included in the <code>MessagePush</code>.
A filter client SHOULD NOT respond to a <code>MessagePush</code>.
Since the filter protocol does not include caching or fault-tolerance,
this is a best effort push service with no bundling
or guaranteed retransmission of messages.
A filter client SHOULD verify that each <code>MessagePush</code> it receives
originated from a service node where the client has an active subscription
and that it matches filter criteria belonging to that subscription.</p>
<hr>
<h1 id="future-work">
Future Work
@ -490,9 +604,18 @@ Note that the current structure of filter requests i.e., <code>FilterRPC</code>
</li>
<li><a href="#adversarial-model">Adversarial Model</a>
<ul>
<li><a href="#protobuf">Protobuf</a>
<li><a href="#protobuf">Protobuf</a></li>
<li><a href="#filter-subscribe">Filter-Subscribe</a>
<ul>
<li></li>
<li><a href="#filter-subscribe-request">Filter Subscribe Request</a></li>
<li><a href="#filter-subscribe-response">Filter Subscribe Response</a></li>
<li><a href="#filter-matching">Filter matching</a></li>
<li><a href="#filter-subscribe-types">Filter Subscribe Types</a></li>
</ul>
</li>
<li><a href="#filter-push">Filter-Push</a>
<ul>
<li><a href="#message-push">Message Push</a></li>
</ul>
</li>
</ul>