Questions about adding switch to Network

[Lox]

Good Day Peeps,

I've got a Dlink DIR655 router and just purchased a 8 port Dlink DGS1008D switch to go with it. Both are Gigabit devices, with 3 coonected devices being Gigabit and the other 2 Mbit.

After reading the manual it tells all about the optimizing the switch, as per below. Note the picture isn't included.

802.1P and QoS
The DGS-1008D Switch supports 802.1p priority queuing Quality of Service. The implementation of QoS (Quality of
Service) and benefits of using 802.1p priority queuing are described here.
Advantages of QoS
QoS is an implementation of the IEEE 802.1p standard that allows network administrators a method of reserving
bandwidth for important functions that require a large bandwidth or have a high priority, such as VoIP (voice-over Internet
Protocol), web browsing applications, file server applications or video conferencing. Not only can a larger bandwidth be
created, but other less critical traffic can be limited, so bandwidth can be saved. The Switch has separate hardware queues
on every physical port to which packets from various applications are mapped to and assigned a priority. The illustration
below shows how 802.1P priority queuing is implemented on the Switch. The eight IEEE 802.1P priority levels defined by
the standard are mapped to the four class queues used in the Switch.
D-Link DGS-1008D Unmanaged Gigabit Ethernet Switch
2
Mapping QoS on the Switch
The picture above shows the default priority setting for the Switch. Class-3 has the highest priority of the four priority
queues on the Switch. In order to implement QoS, the user is required to instruct the Switch to examine the header of a
packet to see if it has the proper identifying tag tagged. Then the user may forward these tagged packets to designated
queues on the Switch where they will be emptied, based on priority.
"The DUT support strict mode for 802.1p QoS. The untagged pkt will follow the priority 0 to work (i.e. class 1)."
Understanding QoS
The Switch has four priority queues. These priority queues are labeled as 3, the high queue to 0, the lowest queue. The
eight priority tags, specified in IEEE 802.1p are mapped to the Switch's priority tags as follows:
• Priority 0 is assigned to the Switch's Q1 queue.
• Priority 1 is assigned to the Switch's Q0 queue.
• Priority 2 is assigned to the Switch's Q0 queue.
• Priority 3 is assigned to the Switch's Q1 queue.
• Priority 4 is assigned to the Switch's Q2 queue.
• Priority 5 is assigned to the Switch's Q2 queue.
• Priority 6 is assigned to the Switch's Q3 queue.
• Priority 7 is assigned to the Switch's Q3 queue.
The Switch uses strict priority for Scheduling. Strict priority-based scheduling, any packets residing in the higher priority
queues are transmitted first.

My question is what does this all mean and how do I implement it? The manual doesn't even say if the priority #'s are the same as the port #'s on the switch.
Obviously I want the network to run as fast as possible and be able to assign priorities to the devices on my network.

TIA

John

 

[archivalbackup]

I'll post some general replies, as I am a Cisco networking engineer and do not know much about the Dlink's capabilities.

You have to have some device in the network that is identifying and tagging the packets with the 802.1p priority tag (COS or QoS depending and are different but beyond the scope here).

In the Cisco world this is called the 'trust boundary' and we generally only trust IP phones to set the tags correctly and not the end hosts, since anyone could set all of their traffic to EF priority to try and take advantage of the QoS mechanisms. In this instance the switch/router is running NBAR or using port numbers / access-lists to categorize and tag traffic.

I doubt the Dlink is actually capable of identifying and marking traffic, from the information you posted it looks like it will only read existing tags and put into the appropriate queue, which means your QoS has to be done on the end hosts, and the applications need to be requesting different levels of service. You may be able to set an entire port to a higher priority, but without sitting down and reading the manual I can't say for sure.

In real life though, if you are running a small network (<250 hosts) and you are only concerned about LAN performance (and not bandwidth management to the internet) you are not going to notice any performance difference if you have QoS or not. Heck I have seen enterprise networks 2,000+ hosts strong that don't implement QoS on the LAN despite my best efforts.