There are two packets AC FIT AP network architecture, a management class is AC AP control message called management packet (also called a control message), the STA is another user data packet, called service packets .
As shown above, the dashed line represents a packet forwarding path. Management packets only transmission in the network between the AC and the AP, the need to go through CAPWAP tunnel forwarding. Service packet transmission between the STA and STA network to be accessed. The presence of two forwarding modes of service packets and forwards (local forwarding) tunnel and forwarding (centralized forwarding), service packets need to go through CAPWAP tunnel forwarding tunnel way forward, straight forward manner without passing through CAPWAP tunnel forwarding.
This issue of sharing content is straight forward and tunnel transmission process of the packet traffic flow both ways, for ease of understanding, we start to understand management processes packet forwarding process.
Management processes packet forwarding process
Conjunction with the following chart to analyze the forwarding process flow management messages. Networking is relatively simple, designed to facilitate the description of the principle.
Figure from top to bottom, right side of the message structure diagram from right to left to see. Payload on the map is seen as the real effective AC information you want to send to the AP, that manage the actual content of the text message. (Forwarding and direct tunnel packet forwarding is for the business in terms of management and direct message forwarding, forwarding tunnel is not half dime, managing only one packet forwarding processing flow.)
First, the package
AC before sending Payload, Payload need to first encapsulated in CAPWAP tunnels. The so-called encapsulated in CAPWAP tunnel, the actual increase is a field outside Payload CAPWAP message, so "looks" as long as there is a message CAPWAP field is considered to be encapsulated in the CAPWAP tunnel.
After increasing CAPWAP field, add UDP / IP fields and fields 802.3, 802.3 field indicates where the packet is to be transmitted via a wired Ethernet.
Finally, AC would also like to give this message plus the management VLAN. The so-called management VLAN , VLAN packets refers to the outer package after CAPWAP added. In the network between the AC and the AP, the management packets will always be with the management VLAN forwarding.
Second, transmission
The actual configuration point of view, between the AC network requires AP management VLAN packets allowed through, in order to ensure the normal transmission of management packets between the AC and AP.
1, if the network between the AC and AP are three network, VLAN management will change the packet forwarding process, the drawing VLAN m '≠ VLAN m. (Here it is performed on an example of Switch 3 forwarding, as easy to remember, m take the first letter of management.)
2, if the network is between the AP and AC Layer network, VLAN management will remain unchanged, in FIG VLAN m '= VLAN m.
Third, decapsulation
When a packet is forwarded from upstream to downstream of the AP directly connected to the interface, i.e. the interface when the connection to the AP, FIG Switch need to remove the outer packet managing the VLAN , and then the rest of the content transmission packet to the AP. By default, the AP can recognize packets without processing management and release management VLAN CAPWAP package, identify specific content management Payload packets.
The actual configuration of the device interface directly connected AP usually require PVID configured to management VLAN, you purpose is in this interface to send packets to the AP when the removed outer layer packet the management VLAN.
Of course, if the interface has no PVID , or AP received packet is with management VLAN , is also a method of coping , this time the need for the AP configuration management-vlan for the management VLAN m, so that AP is received with after the VLAN management packets, or to identify and remove the VLAN management, CAPWAP release package, parses Payload.
The above analysis is the process of AC Management to send the message to the AP, AP process of sending the text to the AC management report, as long as the above process upside down understand it. AP sends packets passing through the CAPWAP encapsulated directly connected to the port to AP, Switch will give the message plus the management VLAN, forwarded to AC. After reaching the AC, the AC remove management VLAN, deblocked CAPWAP package, acquires message information content.
Direct forwarding service packets flow
Forwarding process to analyze traffic flow packets forwarded directly incorporated in the FIG.
Similarly above down right to the left Figure. Payload on FIG valid information is actually transmitted to the STA STA access network device, i.e., the actual content of the service packets. While two AC, if the AC in the transfer station, the formula represents a direct AC network; if the AC party in soy sauce, the representations are hanging beside the AC network; refers to two AC not exist in network. No matter where AC is in the business are in the same packet forwarding path, from the Internet has been forwarded to the STA.
First, the package
Payload will be sent to the STA in the network when entering a package, the package does not mean CAPWAP package, but the increase period and adding a service VLAN 802.3 field outside Payload packets (not reflected UDP / IP field in the drawings, can be understood to have been included in the Payload in). Business VLAN which means the service packet outer VLAN.
Direct forwarding mode, service packets will not be CAPWAP package.
Second, transmission
The actual configuration point of view, the direct forwarding mode, from the upper network to the Internet are to be allowed between the AP traffic by the VLAN packets to ensure the normal transmission of traffic packets between the Internet and the STA.
1, AC direct the networking scenarios, as shown by the AC at the transfer station, after receiving Payload message sent by upper-layer network, and other switches will be only as packet forwarding, encapsulation without CAPWAP, figure transit point for AC received packet switch and receive packet format is the same, and AC switches and also the task of forwarding the same to the next service packet network equipment,
2, hanging next to AC networking scenarios under, as shown in AC in soy sauce at the party, will not receive service message, in this scenario, the service packets do not need to go through AC, and directly through the switch AP forwarded to the STA.
The same business VLAN VLAN There may also be changes in the process of forwarding the case:
1, if the upper-layer network to the Internet is a three-layer networking between the AP, a service VLAN will change the packet forwarding process, the drawing VLAN s' ≠ VLAN s. (Here it is performed on an example of Switch 3 forwarding, as easy to remember, s take the first letter of the service.)
2, if the upper-layer network to the Internet network between the AP is a Layer, the service VLAN remains unchanged, the figure VLAN s' = VLAN s.
The actual configuration point of view, the direct forward mode, from the upper network to the AP are to allow between packets carrying service VLAN through.
Third, remove the service VLAN
When the service packet forwarded from upstream to downstream to the AP, AP received packet should be two treatment, the outer layer of the first service VLAN removed, and then the original 802.11 802.3 field to field, the field 802.11 forwarded the message will indicate that the use of wireless transmission. When processing is complete, AP traffic packet radio transmission to STA.
Fourth, the analytical service packets
After the STA receives the packet service, to remove the outer layer 802.11 fields remaining after Payload field is STA can recognize that the analysis processing of the specific content. Since the STA can not identify a packet with the VLAN, before the AP sends a packet to STA, you must first remove the VLAN service packet.
The above analysis is the process of sending to the STA upper network service packet, STA process of sending packets to the upper layer of the network, but also to reverse the above process to understand it. 802.11 STA field to add the outer packet, sends the packet to the AP in a wireless transmission mode, the AP will receive the first packet format is converted to 802.3, and then add the VLAN service, the network device through the upper levels, forwards the packet transmitted to the destination.
Service packet forwarding processing flow tunnel
Graphs to analyze the service packet forwarding mode tunnel forwarding processing flow of the same look.
Payload is the real effective FIG STA access network device information to the STA, i.e., the actual content of the service message to AC direct-connection network as an example.
First, the package
And as straight forward, the STA will issue Payload encapsulated, encapsulated in a CAPWAP when not enter the network, but the increase was added 802.3 field and Payload outside service VLAN packet (not reflected UDP / IP field in the drawings, can be understood to have been included in the Payload in). Upon completion of service packets sent straight to AC. Tunnel forwarding mode, all service packets must be forwarded to the AC .
After receiving the AC service packet encapsulation will be CAPWAP, the received entire service packet Payload seen as a new, added CAPWAP outer field, increasing the UDP / IP field and the field 802.3. Finally, for the service packet plus the management VLAN. It can be seen during the processing of service packets on the AC during handling and management packets are the same.
In the network between the AC and the AP, the message will remain with the business management VLAN forwarding process.
Second, transmission
Combined with the actual configuration point of view, the way forward tunnel, Internet from the upper to allow the network to carry traffic VLAN packets through the network equipment between the AC, on a network device between the AC and the AP to report the management VLAN allowed pass. To ensure that the service packets can be normally transmitted between the Internet and the STA.
Because the network between the AC and AP Business CAPWAP packet is encapsulated object, service VLAN can be seen as part of the new Payload, the network equipment will not be perceived, so on this network is only allowed on request report management VLAN to pass through can be. As long as the management VLAN through, also packaged by the same business VLAN management VLAN in the.
The same situation VLAN management VLAN changes may also exist in the forwarding process:
1, if the network between the AC and AP are three network, VLAN management will change the packet forwarding process, the drawing VLAN m '≠ VLAN m.
2, if the network is between the AP and AC Layer network, VLAN management will remain unchanged, in FIG VLAN m '= VLAN m.
Third, remove the service VLAN
When a packet is forwarded from upstream to downstream of the AP directly connected to the interface, i.e. when the connection to the AP interface packets need to be removed in FIG outer Switch management VLAN, which then sends the rest of the contents of the message to the AP. If not removed, configure the management-vlan in the AP, this principle and the same process flow management VLAN. Except that the following treatment of AP.
AP CAPWAP addition to releasing the package, but also need to service VLAN removed, and then replaced after the VLAN field of 802.3 to 802.11 packets, because the service packet is sent to the STA, without the need to service VLAN packets by radio transmit to the STA, the STA can eventually receive this data can be identified.
Fourth, the analytical service packets
In the final process and direct forwarding STA mode service parses the message contents, like the STA receives the packet service, to remove the outer layer 802.11 fields remaining Payload field analysis processing can be STA. Also since the STA can not identify a packet with the VLAN, before the AP sends a packet to STA, you must first remove the VLAN service packet.
The above analysis is that the upper tunnel network under way to send a service message forwarding process to the AP, AP sends packets to the upper-layer network process, the above process is also reversed understand it.
Tunnel forwarding mode compared with the advantages and disadvantages of direct forwarding mode
As a direct forwarding tunnel under way and there are different ways of forwarding processing flow of the service packets exist, compared with each other between the two modes, there are some advantages and disadvantages of each. Tunnel forwarding, since all business data needs to be forwarded to the AC, so the AC is easy to centrally manage and control business messages, and because the service packets are encapsulated in the CAPWAP tunnel to improve the safety of the service packets . But also due to all the service packets are forwarded to the AC, the AC high packet processing capacity requirements. Straight forward way forward is just the opposite of the characteristics of the tunnel. Disadvantages comparative table as follows:
| Data forwarding mode |
advantage |
Shortcoming |
| Forwarding tunnel |
AC centralized forwarding data packets, more secure, centralized management and control, easy to deploy new equipment configuration, small changes to the existing network. |
Business data must be encapsulated AC forwarding, packet forwarding efficiency is lower than the direct forwarding mode, AC suffered pressure. |
| Straight forward |
Business data does not require AC package forwarding, packet forwarding high efficiency, AC suffered little pressure. |
Business data is not easy to centrally manage and control the deployment of new equipment to the existing network big changes. |
Network selection tunnel or forwarded directly forwarding, combined with the actual needs and the needs of the current network status in order to choose a more suitable way.
