per packet cost for loads of 1 and 2 drop drastically when the new link is added, the per packet cost increases for higher loads. The MB COIN on the other hand uses the new link efficiently. Notice that the MB COIN's performance is slightly worse than that of the ISPA in the absence of the additional link. This is caused by the MB COIN having to use a learner to estimate the WLU values for potential actions whereas the ISPA simply has direct access to all the information it needs (costs at each link).

| Load   | Net   |
|--------|-------|
| 1      | A     |
| B      |       |
| 2      | A     |
| B      |       |
|        | A     |
| B      |       |
| 4      | A     |
| B      |       |

| ISPA   | MB COIN   |
|--------|-----------|
| 55.50  | 5556      |
| 31.00  | 31.00     |
| 61.00  | 61.10     |
| 52.00  | 51.69     |
| 66.50  | 66.65     |
| 73.00  | 64.45     |
| 72.00  | 72.25     |
| 87.37  | 73.41     |

## 5.3  Butterfly Network

The next network we investigate is shown in Figure 5. It is an extension to the simple

| Load   | Net   |
|--------|-------|
| A      |       |
| 1      | B     |
| 2      | A     |
| B      |       |
| 3      | A     |
| B      |       |
| 4      | A     |
| B      |       |

nnetwork discussed in Section 5.1. We now have doubled the size of the network and have three sources that have to route their packets to two destinations (packets originating at S 1 go to D 1 , and packets originating at S 2 or S 3 go to D 2 ). Initially the two halves of the nnetwork have minimal contact, but with the addition of the extra link two sources from the two two halves of the network share a common router on their potential shortest path.

| ISPA   | MB COIN   |
|--------|-----------|
| 55.41  | 55.44     |
| 20.69  |           |
| 20.69  |           |
| 60.69  | 60.80     |
| 41.10  | 41.10     |
| 65.92  | 66.10     |
| 61.39  | 59.19     |
| 71.10  | 71.41     |
| 81.61  | 69.88     |
