Question : Slow VPN Performance

I was trying to transfer a few very small (10 KB) word docs over the VPN today, and it kept failing after a few minutes. There was very little network activity. I wonder if it is an MTU issue. I used wireshark to get the following:

No.     Time        Source                Destination           Protocol Info
      1 0.000000    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 1 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
      2 0.841445    10.69.69.4            10.69.69.255          NBNS     Name query NB <01><02>__MSBROWSE__<02><01>

Frame 2 (92 bytes on wire, 92 bytes captured)
Ethernet II, Src: AppleCom_9f:1c:06 (00:16:cb:9f:1c:06), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 10.69.69.4 (10.69.69.4), Dst: 10.69.69.255 (10.69.69.255)
User Datagram Protocol, Src Port: 52013 (52013), Dst Port: netbios-ns (137)
NetBIOS Name Service

No.     Time        Source                Destination           Protocol Info
      3 2.000320    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 3 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
      4 4.000199    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 4 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
      5 5.503809    10.69.69.49           10.69.69.51           TCP      [TCP segment of a reassembled PDU]

Frame 5 (1390 bytes on wire, 1390 bytes captured)
Ethernet II, Src: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5), Dst: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f)
Internet Protocol, Src: 10.69.69.49 (10.69.69.49), Dst: 10.69.69.51 (10.69.69.51)
Transmission Control Protocol, Src Port: microsoft-ds (445), Dst Port: 3119 (3119), Seq: 0, Ack: 0, Len: 1336

No.     Time        Source                Destination           Protocol Info
      6 5.683029    10.69.69.51           10.69.69.49           TCP      3119 > microsoft-ds [ACK] Seq=0 Ack=1336 Win=17368 Len=0 SLE=4008 SRE=4160

Frame 6 (66 bytes on wire, 66 bytes captured)
Ethernet II, Src: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f), Dst: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5)
Internet Protocol, Src: 10.69.69.51 (10.69.69.51), Dst: 10.69.69.49 (10.69.69.49)
Transmission Control Protocol, Src Port: 3119 (3119), Dst Port: microsoft-ds (445), Seq: 0, Ack: 1336, Len: 0

No.     Time        Source                Destination           Protocol Info
      7 5.738669    10.69.69.49           10.69.69.51           TCP      [TCP segment of a reassembled PDU]

Frame 7 (1390 bytes on wire, 1390 bytes captured)
Ethernet II, Src: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5), Dst: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f)
Internet Protocol, Src: 10.69.69.49 (10.69.69.49), Dst: 10.69.69.51 (10.69.69.51)
Transmission Control Protocol, Src Port: microsoft-ds (445), Dst Port: 3119 (3119), Seq: 1336, Ack: 0, Len: 1336

No.     Time        Source                Destination           Protocol Info
      8 5.884234    10.69.69.51           10.69.69.49           TCP      3119 > microsoft-ds [ACK] Seq=0 Ack=2672 Win=17368 Len=0 SLE=4008 SRE=4160

Frame 8 (66 bytes on wire, 66 bytes captured)
Ethernet II, Src: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f), Dst: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5)
Internet Protocol, Src: 10.69.69.51 (10.69.69.51), Dst: 10.69.69.49 (10.69.69.49)
Transmission Control Protocol, Src Port: 3119 (3119), Dst Port: microsoft-ds (445), Seq: 0, Ack: 2672, Len: 0

No.     Time        Source                Destination           Protocol Info
      9 5.926810    10.69.69.49           10.69.69.51           TCP      [TCP Previous segment lost] [TCP segment of a reassembled PDU]

Frame 9 (206 bytes on wire, 206 bytes captured)
Ethernet II, Src: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5), Dst: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f)
Internet Protocol, Src: 10.69.69.49 (10.69.69.49), Dst: 10.69.69.51 (10.69.69.51)
Transmission Control Protocol, Src Port: microsoft-ds (445), Dst Port: 3119 (3119), Seq: 4008, Ack: 0, Len: 152

No.     Time        Source                Destination           Protocol Info
     10 5.926844    10.69.69.51           10.69.69.49           TCP      [TCP Dup ACK 8#1] 3119 > microsoft-ds [ACK] Seq=0 Ack=2672 Win=17368 Len=0 SLE=4008 SRE=4160

Frame 10 (66 bytes on wire, 66 bytes captured)
Ethernet II, Src: 00:ff:02:2d:ce:4f (00:ff:02:2d:ce:4f), Dst: 02:ff:b4:9b:b3:e5 (02:ff:b4:9b:b3:e5)
Internet Protocol, Src: 10.69.69.51 (10.69.69.51), Dst: 10.69.69.49 (10.69.69.49)
Transmission Control Protocol, Src Port: 3119 (3119), Dst Port: microsoft-ds (445), Seq: 0, Ack: 2672, Len: 0

No.     Time        Source                Destination           Protocol Info
     11 5.999866    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 11 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     12 7.999410    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 12 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     13 9.999523    00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 13 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     14 11.999763   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 14 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     15 13.999322   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 15 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     16 15.999500   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 16 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     17 17.998949   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 17 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     18 19.999737   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 18 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     19 21.999241   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 19 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

No.     Time        Source                Destination           Protocol Info
     20 23.999534   00:ff:b4:9b:b3:e5     Spanning-tree-(for-bridges)_00 STP      Conf. Root = 32768/02:ff:b4:9b:b3:e5  Cost = 0  Port = 0x8000

Frame 20 (52 bytes on wire, 52 bytes captured)
IEEE 802.3 Ethernet
Logical-Link Control
Spanning Tree Protocol

Answer : Slow VPN Performance

We probably need more information about the network setup.  Type of VPN devices, Internet connection on both ends(T1, DSL, cable) and is this a new problem, in that it worked just fine in the past but today it is crawling.  Looking at your packet cap, 75% of the entries was Spanning Tree, which indicates your switch is spending 75% of it's time looking for the best route to send data.  However, it could be that you had just plugged a device into your switch when you started your capture and it was learning.  I would give it a couple minutes after plugging anything into the switch, then start the capture, then start the VPN and transfer a couple files, then stop your capture.  If STP is still accounting for 75%  of your traffic, you could have a layer 2 problem.