This article is about the following aspect of WAN design.
- Choosing Best WAN Solution
- Internet Backup Soultions
- Remote Access With VPN
Choosing your WAN Solution
While designing the WAN network our goal should be to select the most efficient and best solution for any organization that’s satisfy the customer’s need and requirements . For selecting the WAN solution for any organization you need to have some information related to network design which includes the existing network infrastructure, bandwidth and unified services requirements and cost. For choosing the best WAN remote access solution following table is very helpful which have all the characteristics define against every WAN solution.
| WAN Type | Speed | Bandwidth | Cost | Connection time | Cost/Time | Interference | Reliability | Availability |
| Modem\ ISDN | 56k-128k | Low | Low | High | High | High | Low | High |
| P2P | Low | Low | Low | Medium | Medium | Medium | High | |
| Frame-relay | T1/E1 | Low | Low | Medium | Low-Medium | Medium | High | |
| Lease Lines | 1.54Mbps | Medium | Medium | Medium | Low-Medium | High | High | |
| ATM | High | Medium | Medium | Low-Medium | High | Low | ||
| Wireless/ Microwaves | 54MBSTM-1(155mb)
STM-4 (644mb) Upto 1GB max |
Low-Medium | Low | Low | Medium | Low | Low | |
| MPLS | Depends on connection type | Medium | Medium | Medium | High | Low | ||
| Cable | Depends on cable type like fiber/ethernet | Low-Medium | Low | Low | Medium | Low | Medium |
When to use Frame-relay, ISDN, and Point to point:
For most company you only may need remote access connection for connecting to branch office, email services, for terminal services, for printer and files sharing etc, normally these are low bandwidth requirements. You can choose the low bandwidth solutions from above table for such type of requirements, these solutions are low cost. These solutions include modem/ISDN, Point to point, ADSL, and frame-relay which have medium reliability and high availability and can easily fulfill your basic WAN requirements. Modem or ISDN can provides you a data rate from 56 to 128K where as point to point connection is little costly and normally used for connecting remote offices. Frame-relay is commonly available with different ISPs and you can use frame-relay for unified communication as well. Frame-relay topologies include Hub and spoke, Full Mesh Topology and partial Mesh topology. You can select any of topology according to company’s requirements.
WAN Backup Solutions or Redundancy Methodologies:
For achieving the high availability you may need the different WAN backup solution. Following are the some of the possible solutions that you can use as WAN backup solutions, in case if one WAN link goes down you still have the connectivity to remote office with the other backup solution.
ISDN Dial Backup:
ISDN is a great solution for backup, in figure you can see that we have frame-relay connectivity between the remote offices and just in case if we loss connectivity to remote office then we have on demand ISDN connection as a backup.
Persistent Secondary:
If you have multiple remote offices then you can use the multiple connections between them, you can set high bandwidth connection link as main WAN link while the other low bandwidth links as a secondary WAN link. With the proper configuration you may use these secondary links as backup as well as load balancer.
Shadow PVC:
Shadow PVC are provider by the some ISPs and with become active with some condition like when the total load of main link is increase from certain load level let 50%. Shadow PVC is the virtual circuit through the service provider network and they can be used as when the total load exceed from certain load level.
Linking a Dispersed Enterprise:
As a network engineer you may have to design the layer-2 WAN connection for large enterprise with the dispersed geographic area. You have to transfer the large amount of data over the dispersed sites. For layer-2 WAN connectivity you can use the following protocols or technologies:
- Point to point Links (add these into tech articles)
- SONET/SDH
- DWDM
- DARK Fiber
Point to point Links
The most common method for dispersed enterprise site are point to point links, these are pre-establish WAN connection.
SONET/SDH
A SONET stands for synchronous optical network. It is a standard for linking optical fiber communication systems. This standard creates the high hierarchy of interface rate and allow data stream at different rates to be multiplex. So SONET establish the optical career-level. SONET career can be up to 51.8 MB to 2.48 Gbs, in real world common data rate for SONET is 155MB to 622MB. SONET is standardize by ITUT and define with the name SDH (Synchronous digital hierarchy)
DWDM (Dense wavelength digital multiplexing)
This is an optical technology used for increasing bandwidth over existing optical fiber backbone. DWDM combine the multiple signals at different wavelength on the same fiber at the same time, this is like transforming a single fiber into several or many mini fibers. For example you can multiplex eight OC-48 signals to one fiber to increase the channel capacity of fiber into 5gig to 20Gbs. With DWDM you can transfer data at 400Gbs. With DWDM you can transport different type of traffic from one enterprise edge to other enterprise edge at different speed using the optical cannels. DWDM also provide the cheap WAN solution with higher data rate on fiber optics.
DARK Fiber
Dark fiber is referred to unused optical fiber available for use for fiber communication. The term dark fiber was originally used when referring to the potential network capacity of telecommunication infrastructure. Companies need new line on regular basics.
As a network engineer you need to aware with all the solutions for Dispersed enterprise that we have mention above and you need to choose the best solution that you ISP are providing according to customer requirement.
Connecting WAN with Emerging Technologies
When you looking for WAN solution for your enterprise you can consider the following option for WAN connectivity, but please note some of these solution may not available with ISP.
Best Ethernet Cable for your LAN
