Top Questions

.  .  .  a sampling of questions that seem to pop up from time to time  .  .  .

(will be adding more to this section soon)

3)   BRI dial-backups are very popular - do IXC's offer them ?

Commercially BRI's van be purchased, but IXC's usually merely act as a middelman between the customer and the LEC.   It is true that they are an excellent form of redundancy . . . inexpensive, and usage based. The customer can easily purchase them through the LEC, and "PIC" the service to the IXC.

4)  What Quality can we expect from Video over Frame Relay?

If the bandwidth is high enough, and a dedicated FR access line and PVC is used  - and the provider's Frame Relay network is not congested - then the results are similar to Video over private lines.  At the typical minimum data rate used by customer for video - 384k - the video is surprisingly clear and smooth on a full-size 19" or larger TV screen, and is crystal clear on a small TV or with desktop video on a PC.  The smaller the image, the more "clear" it appears.  For very high-quality, smooth video, a T1 is recommended, with a minimum throughput of 512-to-768 kbps.  

Hint:  for best results, set up the PVC's with either SNA or "Voice" COS (Switch Priority = 9 or 11)

5)  Will the standard Cisco WAN card, the WIC-1T, work overseas ?

Yes, the WIC-1T, although advertised on Cisco's website as working with the T1 interface - also works with the E1 interface.  Be sure to order an X.21 cable for European connections and for most countries, a 240 volt cable (CAB-ACE)..

6)  Is the installation Interval from providers a Guarantee?  Can the customer collect a credit if the interval is exceeded?

No, and No  -  the Interval is an "expected" installation time period, and something that the provider "strives" to acheive.  Although by default there are no credits for late delivery, any contract can be specially written to include such compensation so long as both parties agree to it, and there is a method of enforcement and delivery.  In general this would be not be recommended.

NOTE:  there is, however, a credit is usually available to customers if the provider exceeds the agreed upon MTTR (Mean Time To Repair).


8)  What is the disadvantage with Cisco-based site-to-site IP VPN's?

GRE (Generic Routing Encapsulation)"  -  GRE is a basic tunneling prorocol similar to PPP.  GRE must be used if you want to implement Cisco's higher level routing features and dynamic routing (OSPF, Multicasting, etc.).  Without GRE, only static routing can be used.  Since nearly all implemented IPVPN networks use IPsec encrypted tunnels.  In general, for the Cisco implementation, the IPsec tunnels must be tunneled within GRE tunnels.  

This means the end router has to decrypt and strip off the IPsec headers, then strip off the GRE headers, and then strip off the IP headers in order to access the data.  This adds a large number of CPU cycles.  MNS has tested this implementation and have found that unless a high-end router is used, such as the 7000 series, the CPU utilization skyrockets unless the number of sites is small.  One example, current managed Cisco VPN network with 15 tunnels per site has CPU utilizations being reported at 98%.

9)  What is the disadvantage with Nortel-based site-to-site IP VPN's?

Static Routing.  Nortel Contivity IP VPN networks do not support dynamic routing protocols.  Therefore, with a large network, every time a site is added or removed, every router must be reconfigured manually.