Network Graph Specification

The network graph overview provides a general summary of Shadow's use of a network graph to abstractly model network position and to connect virtual hosts in a network topology while enforcing network characteristics on paths between hosts. This page describes the specific attributes that can be configured in the network graph, and the effect that each attribute has on the simulation.

Example Graph

Below is an example of a simple network graph in the Shadow-supported GML format (note that GML calls graph vertices as nodes, but these terms are generally interchangeable).

graph [
  directed 0
  node [
    id 0
    label "node at 1.2.3.4"
    host_bandwidth_down "100 Mbit"
    host_bandwidth_up "100 Mbit"
  ]
  edge [
    source 0
    target 0
    label "path from 1.2.3.4 to 1.2.3.4"
    latency "10 ms"
    jitter "0 ms"
    packet_loss 0.0
  ]
]

`graph.directed`

Required: False
Default: 0
Type: Integer

Specifies the symmetry of the edges in the graph. If set to 0 (the default), the graph is an undirected graph: an edge between node u and node v is symmetric and can be used to construct a path both from u to v and from v to u. If set to 1, the graph is a directed graph: an edge from node u to node v is assymmetric and can only be used to construct a path from u to v (a separate edge from v to u must be specified to compose a path in the reverse direction).

`node.id`

Required: True
Type: Integer

A unique integer identifier for a given node.

`node.label`

Required: False
Default: n/a
Type: String

An optional, human-meaningful string description of the node. The string may be used in log messages printed by Shadow.

`node.host_bandwidth_down`

Required: True
Type: String

A string defining the downstream (receive) bandwidth that will be allowed for any host attached to this node. Hosts may individually override this value in the Shadow config file. The format of the string specifies the bandwidth and its unit as described in the config documentation, e.g., 10 Mbit. Note that this bandwidth is allowed for every host that is attached to this node; it is not the total bandwidth logically available at the node (which is not defined).

`node.host_bandwidth_up`

Required: True
Type: String

A string defining the upstream (send) bandwidth that will be allowed for any host attached to this node. Hosts may individually override this value in the Shadow config file. The format of the string specifies the bandwidth and its unit as described in the config documentation, e.g., 10 Mbit. Note that this bandwidth is allowed for every host that is attached to this node; it is not the total bandwidth logically available at the node (which is not defined).

`edge.source`

Required: True
Type: Integer

The unique integer identifier of the first of two nodes of the edge. The node must exist in the graph. If the graph is directed, this node is treated as the source or start of the edge.

`edge.target`

Required: True
Type: Integer

The unique integer identifier of the second of two nodes of the edge. The node must exist in the graph. If the graph is directed, this node is treated as the target or end of the edge.

`edge.label`

Required: False
Default: n/a
Type: String

An optional, human-meaningful string description of the edge. The string may be used in log messages printed by Shadow.

`edge.latency`

Required: True
Type: String

The latency that will be added to packets traversing this edge. This value is used as a weight while running Dijkstra's shortest path algorithm. The format of the string specifies the latency and its unit, e.g., 10 ms. If a unit is not specified, it will be assumed that it is in the base unit of "seconds". The latency must not be 0.

`edge.jitter`

Required: False
Default: n/a
Type: String

This keyword is allowed but currently nonfunctional; it is reserved for future use.

`edge.packet_loss`

Required: True
Type: Float

A fractional value between 0 and 1 representing the chance that a packet traversing this edge will get dropped.

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