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Testing of VLANs over Hybrid Circuits
USN capabilties are utilized in carrying out several experiments using Virtual Local Area Networks (VLAN) over layer-1 (SONET) and layer-3 (IP) dedicated connections. These experiments enabled us to make some important observations:
A. VLANs for Data-Plane Alignment for Layer 1-3 Connections: We demonstrated that layer 1 and 2 connections (e.g. povisioned on networks such as USN, CHEETAH and HOPI) can be composed with layer-3 connections (e.g. provisioned by OSCARS) using VLANS; this composition is achieved by simple cross-connect on a layer-2 switch.
B. Jitter and Dynamic Characteristics VLANs over SONET, IP and Composite Connections:
- We studied jitter and other dynamic characteristic of VLANs over SONET connections, which showed that jitter levels are somewhat independent of the connection length;
- We compared the jitter and dynamic charactersitics of VLANs over SONET with VLAN over IP for dedicated connections; as expected, the jitter levels of the former are much lower making them preferred candidates for instrument control and computational steering applications; and
- We observed that when VLANs are composed of layer-1 and layer-3 components, the overall jitter levels had a dampening effect. By using a normalization method, we could show that the jitter level of the composite VLAN is lower than that of VLAN over a layer-3 connection of similar length.
These resutls are briefly summarized in the following:
We are currently carrying out more experiments and analysis on these aspects. The above results were summarized at USN - Update Presentation at 2006 Summer ESCC Meeting.
Brief Description of Experimental Setup
- SONET (OC-21) channels of lenghts 1000, 2000, 3000, and 4000 miles were setup on USN using core Ciena CDCI switches. These channels were terminated at both ends on Force10 E300 switches that provided VLAN tagging. There were other connections on USN during these experiments, whcih had no influence on these VLANS.
- MPLS tunnel (1Gbps) was set up between ORNL and Atlanta-SOX using Juniper T-640 routers at each location, which provided VLAN tagging. These are production routers but their cross traffic has no apparent effect on the performance of this tunnel.
- Composite VLAN over SONET and MPLS connections were implemented by terminating one end of each on Force10 E300 at ORNL and cross-connecting them using a local-VLAN.
- Hosts were connection at each end of VLAN in each of the above cases and two types of measurements were collected: (a) standard ping measurement between the hosts, and (b) round-trip delay of 1K byte message sent via TCP socket connection beween a client on one host and a sever on the other.
The following is the setup used in our experiments:
More details of the experimental setup are provided in ourUSN - Update Presentation at 2006 Summer ESCC Meeting.
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