The Mesh Comparison

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The Mesh Comparison

PLANET’s Layer 3 MAP products

v.s. 3rd’s Layer 2 Mesh

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Outline

• IP Subnet Planning• Self-healing• Case Study

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IP Subnet Planning

• Before planning, the difference between layer 3 and layer 2 is based on different information to transmit packets– Layer 2 is based on MAC layer information– Layer 3 is based on IP layer information

• The pros and cons of layer 2 communication– High performance since the equipment only processes layer 2

information– All devices must be in the same IP segment– Unable to effectively avoid broadcast storm caused by

broadcast domain and NetBEUI– Packets transmitted with hop count

• The pros and cons of layer 3 communication– Requires more system resource– No limitation in IP usage– Uses routing protocol to eliminate broadcast storm– One hop route

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Self-healing

• Layer 2 solution– It is the logical result in such solution

User 1

User 2

When user 1 sends packet to user 2, the Relay 2 will forward the packet to Relay 1, Gateway, and Relay 3, then Relay 3 forwards to User 2.

However, if the wireless connection between Relay 2 and Relay 3 is gone, the process, still the same, will be Relay 2 forwards the packet to Relay 1 and Gateway, and Gateway forwards to Relay 3, then to User 2.

Of course, the packet reaches destination eventually, but it takes longer time and causes more network traffic. Because of it need to follow the tree algorithm.

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Self-healing

• Layer 3 solution– There is always one route for every packet

When user 1 sends packet to user 2, the Relay 2 will only forward the packet to Relay 3 according to their route tables.

However, if the wireless connection between Relay 2 and Relay 3 is gone, the process will be Relay 2 forwards the packet to Gateway, and Gateway forwards to Relay 3, then to User 2.

This algorithm guarantees the reach of packet with the optimal path, and generates no extra loading. Because it adopt MDOLSR and is layer 3 routing.

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Management

• Layer 2– Web interface only– Some third party provide management software with additional cha

rge

• PLANET solution– Web interface is the basic

• HTTPS secured access– SNMPv3 supported

• Also secured access– Central management software as standard pakets for the products

• No restrictions of license consideration• PPTP secured VPN access• SNMPv3 secured management

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Management

• Central Management Software– Standard package, no additional charge or

restriction– Secured Access

IP group 1 (Backhaul)

IP group 3

IP group 5

For security reason, only in the secured IP group 1 can the manager fully control the whole mesh APs through central management software.

Otherwise, the users can only manage one by one. This shall provide un-authorized users effect the whole network.

ManagerLogin to the backhaul network thru. PPTP VPN

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Case Study

• Example network– 200 users– 1 Gateway– 3 Relays

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• Layer 2 solution– So-called Bridge or Repeater connection– All equipments are in the same IP segment

• The 204 (or 201 for some third party solution) IP addresses must be in the same segment

• It requires a C-class IP segment– One packet will generate four times (or more) loading to the

whole network• Each packet needs to be sent to every mesh node in order to find its

destination– The packets are not transmitted with the shortest paths

• Layer 2 does not define such mechanism– Tree topology

• Network users access Internet with specified root AP (Gateway)

• It is no a problem when there exists only one Gateway

Case Study

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• Layer 3 solution– The Backhaul connection and every Local Access are using independent IP segments

• In this case, the total 204 IPs are in five IP groups

IP group 2

IP group 1 (Backhaul)

IP group 3

IP group 4

IP group 5

Case Study

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• Layer 3 solution– The packet always transmits along with the shortest path

• The routing protocol used by PLANET Mesh is called the MDOLSR algorithm (Modified Dynamic Optimized Link State Routing)

• This protocol determines the best route for every packet

– No unnecessary traffic is generated– Expand the coverage or add-on new AP node is just like add a new IP subnet– One hop routes

Case Study

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• When network grows– 200 users → 500 users– 1 Gateway → 2

Gateways– 3 Relays → 5 Relays

Case Study

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• Layer 2 solution– All equipments are in the same IP segment

• The 507 IP addresses must be in the same segment• The originally planned C-class IP segment is not sufficient• The administrator must have a thorough IP plan to prevent confliction

– One packet will generate much more loading to the whole network• The network is congested with useless packets, thus effects the

performance– Tree topology

• Network users access Internet with specified root AP (Gateway)• The two Gateways cannot dynamically share the overall Internet loading• If one Internet connection fails, the users won’t be redirected to another

Gateway automatically– It is also questionable that whether a layer 2 solution can have more

than 1 Gateway, and how about its operative and efficiency.

Case Study

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• Layer 3 solution– There are eight IP groups for the 507 IP addresses– The Auto-IP design eases the IP allocation efforts– No need to re-organize the whole IP network even more mesh APs added– The network bandwidth is utilized even the nodes are increasing– Benefits from two Gateways

• Dynamic load balance • Fail over

Case Study

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The Mesh Comparison

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