Hi there!
Choosing the most appropriate switch can be a cumbersome and difficult task, especially if you've got a wide range of operations and user wishlists to cover. Today I’ll try to simplify the process for you so you can choose the switch that matches your tailored requirement.
STEP 1
Chose the power type you have in your datacenter / IT room. See if you have AC power or DC power. Based on that, choose the power cable required.
Secondly, see if you require a redundant power or single power supply. As a suggestion, always go for the redundant power supply whenever there is a possibility. This is to make sure that if there is a power outage on one line or there is a power supply failure, the switch can still work with the redundancy provided.
If selected switch doesn’t support secondary power supply, try to add an “ATS” device. This device basically has 2 inputs and a single output. You can use the output to give power to the switch and use the inputs to get the power from 2 different sources or locations.
STEP 2
Calculate what kind of downlink ports are required. Huawei offers multiple variants, as shown below:
FE Electrical;
GE Electrical;
GE Optical;
10GE Electrical;
10GE Optical;
Multi-GE Electrical;
25GE Optical.
STEP 3
Calculate what kind of uplink ports are required. Huawei offers multiple variants, as shown below:
FE Electrical;
GE Electrical;
GE Optical;
GE Combo;
10GE Optical;
40GE Optical;
100GE Optical;
25GE Optical.
STEP 4
Check with the requirement team how many ports are required on a switch. Huawei has following ranges available on access switches:
5-10;
12-18;
20-36;
44-52;
>52.
STEP 5
Now that the hardware has been decided, check what kind of features are required on the switch. Thef following high-level features are offered (a lot more features are available, but these are the major ones that help in the categorization of the switches):
PoE;
IPv6;
VxLAN;
iStack.
STEP 6
You can also choose which series they should be from, like from LI series, SI series, EI Series or HI Series. LI Series is about basic L2 switches, SI are basic L3 switches, EI switches provide complete L3 features and HI offers advanced L3 features on a switch.
By performing all these steps, you can select the switch meeting all your requirements. To make things simpler, Huawei also offers the same in the Unistar app. You can access it here. This tool looks like this:
Source: Huawei SCT Page
STEP 7
After completing the above steps, you might end up with more than one options to chose a switch from. Now, to further narrow our search down and chose the most appropriate switch, we have to go through one final detailing step.
We’ll calculate the switch throughput and forwarding capacity to get the best results. We can calculate the throughput by using the following method:
1. calculate the type of ports required - that is, see if you need 100M/1G/10G ports;alculate the number of ports required.
2. note that you might end up with a mixture of ports (some will be 1G, others 10G and even 40G) and that’s okay;
3. now we’ll calculate the throughput requirement:
Switch throughput = Number of ports * type of ports*2
You might ask, why multiply it by 2 - it is because the port throughput is normally marketed at half-duplex and the switch is configured at full-duplex, thus doubling the throughput of the port.
For example, you need a 24-port switch with 24 x 1G downlink ports and 4 x 10G uplink ports, so we’ll calculate the throughput requirement in this way:
Switch Throughput = (24 x 1 + 4 x 10) *2
= (24 + 40)*2
= 64 * 2
Switch Throughput = 128 Gbps
The next step will be to calculate the forwarding capacity of the switch. The forwarding capacity means how many packets per second a switch can forward. The Ethernet packet sizes are limited because Ethernet conflict detection mechanisms are enabled and as per the standard, the minimum data frame has to be 84 bytes. It is calculated using the following:
Minimum data packet size: 64 bytes
Inter-frame gap: 12 bytes
Preamble bytes: 8 bytes
Total: 64 + 12 + 8 = 84 bytes
Take the 1 Gbit/s Ethernet interface as an example. Every 8 bits form a byte. Therefore, the Ethernet interface rate of 1000 Mbit/s =125 Mbyte/s, that is, the Ethernet interface can forward 125M bytes =12,500,000,000 byte per second. Assuming that all data frames transmitted in the worst case scenario are the smallest 84 byte, the data frame forwarded by the 1000 Mbit/s Ethernet port per second is 12500000000/84=148,809,524pps (frame/second) =148.8Mpps=1.488Mpps.
Therefore, it can be concluded that the packet forwarding rate of the 1000 Mbit/s Ethernet interface is 1.488Mpps, then the packet forwarding rate of the 10G Ethernet interface is 14.88Mpps.
For example, if there is a 48-port 10/100/1000 Base-TX Ethernet switch, the packet forwarding rate of the switch is 48*1.488Mpps=69.5Mpps, plus four 10GE ports 4*14.88Mpps=59.52Mpps. So, the total is 69.5Mpps+59.52Mpps=129.02Mpps. That is, a 48-port 1000 Mbit/s + 4x10G Ethernet switch can implement line-rate forwarding only when the packet forwarding rate of the entire device reaches 129.02Mpps.
STEP 8
Now, that you have selected the switch, there might be some extra customer requirements like WLAN licenses or MACSec requirements on the switch. For these, you should select the “H” series switches; that provides the highest level of features available in the L3 switch.
CONCLUSION
Selecting an appropriate switch is as critical as the network function itself, because choosing a high-end switch will drive the cost up, while choosing a low-end switch means compromising on the services. So, using these steps, you can choose the switch with 100% accuracy.
Hope this helps. In case of any questions, please do let me know in the comments!
