Page 2 / 14 Outline IP Subnet Planning Self-healing Case Study
Page 3 / 14 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
Page 4 / 14 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.
Page 5 / 14 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.
Page 6 / 14 Management Layer 2 –Web interface only –Some third party provide management software with additional charge 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
Page 7 / 14 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. Manager Login to the backhaul network thru. PPTP VPN
Page 8 / 14 Case Study Example network –200 users –1 Gateway –3 Relays
Page 9 / 14 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
Page 10 / 14 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
Page 11 / 14 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
Page 12 / 14 When network grows –200 users → 500 users –1 Gateway → 2 Gateways –3 Relays → 5 Relays Case Study
Page 13 / 14 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
Page 14 / 14 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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