Page 41 - ITUJournal Future and evolving technologies Volume 2 (2021), Issue 1

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 1

0.3 100
No Reconfiguration - BE-0.1ρ L
No Reconfiguration - BE-1.0ρ L 90
0.25 No Reconfiguration - BE-2.0ρ L 80
Mean Packet Delay (ms) 0.15 No Reconfiguration - ST-0.1ρ L % Admission 70 Reconfiguration ST τ = 2
Reconfiguration - BE-0.1ρ L
Reconfiguration - BE-1.0ρ L
Reconfiguration - BE-2.0ρ L
0.2
No Reconfiguration - ST-1.0ρ L
No Reconfiguration - ST-2.0ρ L
Reconfiguration - ST-0.1ρ L
60
Reconfiguration - ST-1.0ρ L
Reconfiguration - ST-2.0ρ L
50
Reconfiguration ST τ = 3
0.1
Reconfiguration ST τ = 4
Reconfiguration ST τ = 5
40
0.05
No Reconfiguration - ST τ = 3
30 No Reconfiguration - ST τ = 2
No Reconfiguration - ST τ = 4
No Reconfiguration - ST τ = 5
0 20
2 4 6 8 10 12 14 16 18 20 2 4 6 8 10 12 14 16 18 20
Stream Mean Rate π (Streams/Second) Stream Mean Rate π (Streams/Second)
(a) = 2
Fig. 14 – CentralizedBidirectionalTopology: Streamadmissionpercent‑
0.3 age for TAS with centralized con iguration (CNC) management.
No Reconfiguration - BE-0.1ρ L
No Reconfiguration - BE-1.0ρ L
0.25 No Reconfiguration - BE-2.0ρ L 0.06 Reconfiguration - ST τ = 2
Mean Packet Delay (ms) 0.15 No Reconfiguration - ST-1.0ρ L 0.04 No Reconfiguration - ST τ = 2
Reconfiguration - BE-0.1ρ L
Reconfiguration - BE-1.0ρ L
Reconfiguration - ST τ = 3
Reconfiguration - BE-2.0ρ L
Reconfiguration - ST τ = 4
0.2
0.05
Signaling Overhead (Mbps)
No Reconfiguration - ST-0.1ρ L
Reconfiguration - ST τ = 5
No Reconfiguration - ST-2.0ρ L
No Reconfiguration - ST τ = 3
Reconfiguration - ST-0.1ρ L
No Reconfiguration - ST τ = 4
Reconfiguration - ST-1.0ρ L
No Reconfiguration - ST τ = 5
Reconfiguration - ST-2.0ρ L
0.1
0.03
0.05
0 0.02
0.01
2 4 6 8 10 12 14 16 18 20
Stream Mean Rate π (Streams/Second)
0
2 4 6 8 10 12 14 16 18 20
(b) = 5
Stream Mean Rate π (Streams/Second)
Fig. 12 – Centralized Bidirectional Topology: Mean end‑to‑end delay Fig. 15 – Centralized Bidirectional Topology: Average stream signaling
for ST and BE traf ic for varied mean stream lifetime for different BE overhead for TAS with centralized con iguration (CNC) management.
loads , and ST stream rates .
tional ring compared to the unidirectional ring are more
0.3
modest (roughly 20%). This is mainly because the initial‑
0.25 ized gating ratio is too restrictive and severely underuti‑
Max Packet Delay (ms) 0.15 No Reconfiguration - ST-Max τ = 2 are not included due to space constraints that different BE
lizes the links. We found in additional evaluations that
0.2
Reconfiguration - ST-Max τ = 2
loads do not impact the ST stream performance due to
Reconfiguration - ST-Max τ = 3

Reconfiguration - ST-Max τ = 4
the TAS operation, i.e., TAS effectively partitions the traf‑
Reconfiguration - ST-Max τ = 5
0.1
No Reconfiguration - ST-Max τ = 4
No Reconfiguration - ST-Max τ = 5
traf ic).
0.05 No Reconfiguration - ST-Max τ = 3 ic at the egress switch/port (BE traf ic does not block ST
Similar to the unidirectional ring, the bidirectional
0 ring topology provides constant signaling delay (around
2 4 6 8 10 12 14 16 18 20 3.5 s) due to the CNC out‑of band signaling channels. The
Stream Mean Rate π (Streams/Second)
average signaling delay is slightly lower than in the unidi‑
Fig. 13 – Centralized Bidirectional Topology: Maximum ST packet delay rectional ring (which had a signaling delay around 4 s),
for TAS with centralized con iguration (CNC) management. mainly since the signaling hop distances in the bidirec‑
tional ring are shorter than in the unidirectional ring.
at the initialized value (20% of CT, i.e., 10 s), resulting in
a constant maximum delay of around 50 s, albeit at the Fig. 15 shows the signaling overhead. Since the bidirec‑
expense of rather low admission rates, see Fig 14. tional ring topology is effectively the same as the uni‑
directional ring topology (albeit having another port to
Fig. 14 shows the stream admission ratio (percentage). the switch), the signaling overhead in the bidirectional
With the high stream generation rate = 20 streams/s ring network is in general very similar to the signaling
and long average stream lifetime = 5 s, the admission overhead in the unidirectional topology. Note that while
rate is still slightly above 90% for the bidirectional topol‑ the hop traversal is reduced (since the stream can take
ogy with CNC recon iguration. The bidirectional ring thus one of two paths to the destination governed by short‑
achieves a substantially increased (close to 50% higher) est path, i.e., the smallest hop count), the number of sent
admission rate compared to the unidirectional ring exam‑ and received CDT frames are generally the same. Simi‑
ined in Fig. 8. In contrast, the increases of the admission lar to the unidirectional topology, the recon iguration ap‑
ratio of the no recon iguration approach with the bidirec‑ proach generates more CDT traf ic. Note that admissions
© International Telecommunication Union, 2021 25