// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.overnet.protocol;

/// If a LinkStatus or NodeStatus version is set to this value, that link or node
/// is considered dead and should be expunged soon.
const uint64 METRIC_VERSION_TOMBSTONE = 0xffffffffffffffff;

/// Description of a single node.
table PeerDescription {
    /// The set of services published by this node.
    1: vector<string> services;
};

/// Metrics associated with a link.
/// Note that a link is a uni-directional connection between two nodes.
table LinkMetrics {
    /// How much bandwidth is currently available across a link (in bits per second).
    1: uint64 bw_link;
    /// How much bandwidth is currently in use across the link (in bits per second).
    2: uint64 bw_used;
    /// Current round trip time for requests across this link.
    3: uint64 rtt;
    /// Maximum send size for a datagram across this link.
    4: uint32 mss;
};

/// Status packet for a single link.
/// Traffic on the link flows from `from` to `to`.
struct LinkStatus {
    /// Link originating node.
    NodeId from;
    /// Link target node.
    NodeId to;
    /// An identifier (chosen by node `from`) to label this link.
    /// `from` must guarantee that the tuple (from, to, local_id) is unique
    /// for each of it's held links.
    uint64 local_id;
    /// A monotonically increasing version counter for this links status.
    uint64 version;

    /// Metrics associated with this link.
    LinkMetrics metrics;
};

/// Metrics associated with a node.
table NodeMetrics {
    /// How long does this node take to forward a message between two links?
    1: uint64 forwarding_time;
};

/// Status packet for a node.
struct NodeStatus {
    /// The node to which we refer.
    NodeId id;
    /// A monotonically increasing version counter for this nodes status.
    uint64 version;

    /// Metrics associated with this node.
    NodeMetrics metrics;
};