Topologies

Dumbbell Topology

The dumbbell topology connects \(k=1,\dots,K\) node pairs through a single, shared bottleneck link \(l_{K+1}\). The \(K\) node pairs compete for the available bottleneck bandwidth. The propagation delays between node pairs can differ.

Dumbbell network topology with K host pairs: Source nodes s₁, s₂, …, n_K transmit via K access links to a gateway node that forwards the K flows over one link to another gateway node, which forwards each of K flows to their corresponding destination nodes d₁, d₂, …, d_K.

The dumbbell network has the following parameters:

Parameter	Description
`bw`	Bottleneck bandwidth
`error`	Packet loss probability
`qlen`	Bottleneck queue length
`qdisc`	Bottleneck qdisc
`rtts`	Two-way propagation delays

The rtts parameter is a list of length \(K\) such that the \(k\)-th node pair has a two-way propagation delay of \(\texttt{rtts}[k]\).

Paths

A path is a sequence of links a packet traverses from its source to its destination. Paths have parameters that model the end-to-end transmission properties:

Name	Symbol	Description	Unit
Path capacity	`bw`	Data rate of the bottleneck link	bit/s
One-way propagation delay	`OWD`	One-way propagation delay	s
Bottleneck queue size	`qlen`	Queue size of the bottleneck link	packets
Queueing discipline at bottleneck	`qdisc`	Packet scheduler at the bottleneck link	–
Packet error probability	`loss`	i.i.d. packet drop probability of the path	%

ccperf uses paths with parameters that partially originate from Pantheon and the Wideband InterNetworking engineering test and Demonstration Satellite (WINDS).

Name	`bw`	`OWD`	`loss`	`qlen`	`qdisc`
default	8.00	30	0	20	FIFO
India to AWS India	100.42	27	0	173	FIFO
AWS Korea to China	77.72	51	0.0006	94	FIFO
AWS California to Mexico	114.68	45	0	450	FIFO
WINDS Satellite	42.00	400	0.0074	2800	FIFO
Nepal to AWS India	Poisson(0.57)	28	0.0477	14	FIFO
Mexico cellular to AWS California	Poisson(2.64)	88	0	130	FIFO
AWS Brazil to Colombia cellular	Poisson(3.04)	130	0	426	FIFO