WAN Considerations
DIA — Direct Internet Access
- An ordinary connection to the Internet
Leased Lines
- Point-to-point
- Logically “a wire” between two sites
- ISP makes the wire look continuous
- Usually
- Based on T-Carrier, or OCx technology
- Takes months to provision
- Older tech
- Very private (only the ISP can see the data)
- Sometimes requires construction to provision
- Always more expensive, but reliable and dedicated bandwidth
- Gets more expensive with a SLA
T-Carrier
- Leased line
- Invented in the 1950s, used to link telephone central offices and transport telephone calls
- Completely private
- Dedicated Bandwidth
- Expensive
- Old cell-towers still sometimes require handoff via a T-Carrier
- Very few of these still exist
| Level | Signal | Line Rate | DS0 Voice Channels | Composition |
|---|---|---|---|---|
| T1 | DS1 | 1.544 Mbps | 24 | 24x DS0 |
| T2 | DS2 | 6.312 Mbps | 96 | 4x T1 |
| T3 | DS3 | 44.736 Mbps | 672 | 7x T2 (28x T1) |
| T4 | DS4 | 274.176 Mbps | 4,032 | 6x T3 (168x T1) |
SONET
- Leased Lines
- Uses a ring to provide built-in redundancy
- 50ms failover time
- Higher uptime than other technologies
- Expensive. Extremely expensive dedicated links
| OC Level | Speed |
|---|---|
| OC-1 | 51.85 Mbps |
| OC-3 | 155.52 Mbps |
| OC-12 | 622.08 Mbps |
| OC-24 | 1.244 Gbps |
| OC-48 | 2.488 Gbps |
| OC-192 | 9.952 Gbps |
| OC-255 | 13.21 Gbps |
MPLS
- Less expensive than a leased line
- Much faster
- Gets expensive when a SLA is required
MPLS Layer 3 VPN
- Can be multi-site
- Relatively cheap
- Requires peering with the provider who carries the routes between sites
MPLS Layer 2 VPNs
- Always more expensive.
- Required if your App needs direct adjacency
- Required if you want to do your own routing (peer with just your own nodes)
VPWS — Virtual private wire service
- Point-to-point
VPLS — Virtual Private LAN Service
- Full-Mesh
Metro Ethernet
- Can be very fast, 10Gbps and above
- Can also offer high SLA
- Usually easy to ask for more bandwidth
Fiber Technologies
DWDM
- Usually owned by the ISP as the multiplexers are very, very expensive
- A single fiber can support multiple channels
- A single channel can support 10 to 400G
- Tight channel spacing. (Less than 1nm)
- 80+ channels
- Used to link continents with submarine cables
- Can multiplex wavelengths of light in channels
- Unknown theoretical speed
CWDM
- Channels are widely spaced
- 20 nm
- Significantly cheaper that DWDM
- 18 channels is common
Dark Fiber
- The DIY Solution
- A business asks an ISP “do you have any fiber I can just .. use?”
- The ISP goes “yeah, but … it’s your problem.”
- Dark fiber is service-less
- Dark fiber is literally a glass pipe
- Dark fiber doesn’t have a SLA
- Dark fiber means bringing your own optics, your own transceivers, your own signal regenerators. Anything an ISP would ordinarily provide or cover
- Very secure once running
- Tends to be cheaper
Cloud
- Cloud Connect: Not Internet, but a direct connection to something like AWS, Azure, or Google Cloud.
- Cloud On-Ramp: A similar connection, but made via SD-WAN over DIA.
Cellular Wireless
- If there are two numbers, the slower one is the upload.
- These need to be secured via IPSec or another Overlay Technology.
Slow
GSM
-
9600bps
-
~1h to transfer 5MB
-
GPRS
-
128 Kbps
-
~5 minutes to transfer 5MB
-
UMTS (3G)
-
1Mbps
-
~8 seconds to transfer 5MB
OK
LTE
- 300/50 Mbps
- ~1 hour to upload a 20GB file
LTE Advanced
- 600/100 Mbps
- ~30 minutes to upload a 20GB file
LTE Advanced Pro
- 1.1GB/200 Mbps
- ~15 minutes to upload a 20GB file
Modern
5G
- 20/10 Gbps
- ~16 seconds to upload a 20GB file
Overlay Technologies
IPSec
- IPSec doesn’t support routing protocols unless encapsulated in GRE
GETVPN
- Doesn’t change the outside IPs
- Does not make an overlay network
- Native Multicast