Establishing ECC Routes
The HWECC solution adopts the shortest path first algorithm to establish ECC routes.
In this context, the shortest path refers to the path with minimum number of stations. The following describes how an NE establishes ECC routes:
1. The physical layer of an NE maintains the status information of the DCC to which each line port corresponds.
2. The MAC layer of the NE establishes the MAC connection between the NE and the adjacent NE.
The steps are as follows:
a. The NE broadcasts the connection request frame (MAC_REQ) to the adjacent NE in a periodical manner.
b. After receiving the MAC_REQ, the adjacent NE returns the connection response frame (MAC_RSP).
c. If the MAC_RSP is received within the specified time, the NE establishes a MAC connection between the NE and the adjacent NE.
3. The network layer of the NE establishes the network layer routing table.
The steps are as follows:
a. According to the status of the MAC connection, the NE establishes an initial network layer routing table.
b. The NE broadcasts its routing table to the adjacent NE in a periodical manner through the routing response message.
c. The adjacent NE updates its network layer routing table according to the received routing response message and the shortest path first algorithm.
d. At the next route broadcasting time, the NE broadcasts its current network layer routing table to the adjacent NE.
Figure 1 Networking example for establishing ECC routes
The following describes how to establish ECC routes between NEs. The network shown in Figure 1 is provided as an example.
1. The physical layer of each NE maintains the status information of the DCC to which each line port corresponds. The physical layer of each NE detects that there are two available DCCs.
2. The MAC layer of the NE establishes the MAC connection between the NE and the adjacent NE.
NE1 is considered as an example to describe how to establish the MAC connection.
a. NE1 broadcasts the frame MAC_REQ to NE2 and NE5 in a periodical manner through its two available DCCs. The frame MAC_REQ contains the ID of NE1.
b. After receiving the frame MAC_REQ, NE2 and NE5 return their respective MAC_RSP frames. The frame MAC_RSP from NE2 contains the ID of NE2 and the frame MAC_RSP from NE5 contains the ID of NE5.
c. After receiving the MAC_RSP frames, NE1 establishes a MAC connection between NE1 and NE2 and a MAC connection between NE1 and NE5 according to the NE ID, DCC that reports the frame, and other information.
3. The network layer of the NE establishes the network layer routing table.
NE1 is considered as an example to describe how to establish the network layer routing table.
a. According to the status of the MAC connection, NE1 establishes an initial network layer routing table. In the routing table, there are two routes, one to NE2 and one to NE5.
b. NE1 broadcasts its routing table to adjacent NEs in a periodical manner through the routing response message.
c. After receiving the routing response message from NE1, NE2 and NE5 update their respective network layer routing tables. After the update, there is a route to NE5 in the network layer routing table of NE2, and the transfer NE is NE1. There is a route to NE2 in the network layer routing table of NE5, and the transfer NE is also NE1.
d. Similarly, NE1 also adds the routes to NE3 and NE4 in its NET layer routing table according to the routing response messages from NE2 and NE5. There are two routes between NE1 and NE3. The distance of the route whose transfer NE is NE2 is 1 and the distance of the route whose transfer NE is NE5 is 2. Hence, according to the shortest path first principle, only the route whose transfer NE is NE2 is retained in the network layer routing table. The routes to NE4 are processed in the same way as those to NE3.
e. If the DCC between NE1 and NE2 becomes faulty, the MAC connection between NE1 and NE2 fails. In this case, NE1 updates the routes to NE2 and NE3 in its network layer routing table according to the routing response message from NE5. Hence, the routes to NE2 and NE3 are re-established. In this way, the ECC route is protected.
Transferring Messages
In the HWECC solution, the messages between NEs are transferred at the network layer of the NEs.
Figure 1 illustrates how the HWECC solution transfers the messages originated from the U2000 to a destination NE.
The implementation principle is as follows:
1. The U2000 transfers application layer messages to the gateway NE through the TCP connection between them.
2. The gateway NE extracts the messages from the TCP/IP protocol stack and reports the messages to the application layer.
3. The application layer of the gateway NE queries the address of the destination NE in the messages. If the address of the destination NE is not the same as the address of the local station, the gateway NE queries the core routing table of the network layer according to the address of the destination NE to obtain the corresponding route and the communication protocol stack of the transfer NE. As the communication protocol stack of the transfer NE in Figure 1 is HWECC, the gateway NE transfers the messages to the transfer NE through the HWECC stack.
4. After receiving the packet that encapsulates the messages, the network layer of the transfer NE queries the address of the destination NE of the packet. If the address of the destination NE is not the same as the address of the local station, the transfer NE queries the network layer routing table according to the address of the destination NE to obtain the corresponding route and then transfers the packet.
5. After receiving the packet, the network layer of the destination NE reports the packet to the application layer through the Layer 4 because the address of the destination NE of the packet is the same as the address of the local station. The application layer functions according to the message sent from the U2000.
Figure 1 Implementation principle of message transferring (HWECC)
Extended ECC
The extended ECC refers to the ECC protocol stack that is loaded on the TCP/IP protocol stack. That is, the HWECC protocol stack is carried through the extended channel (such as Ethernet) instead of the DCC channel to meet the requirements of special scenarios.
The difference between the extended ECC and the ECC is that the physical layer of the ECC is the DCC channel and that of the extended ECC is an extended channel (such as Ethernet channel). As shown in Figure 1, subnet 1 and subnet 2 are independent networks that are connected with a HUB instead of a fiber. The NEs of subnet 2 are managed by the gateway NE of subnet 1.
Figure 1 Networking that involves only Huawei equipment
The extended ECC establishes the MAC connection of adjacent NEs through the TCP connection. The ECC can be extended in the automatic mode or the manual mode.
The implementation principle of the automatic ECC extension is as follows:
1. Each NE obtains the IP addresses of other NEs that are on the same Ethernet through the address resolution protocol (ARP).
2. The NE with the largest IP address automatically functions as the server and detects the TCP requests from the clients.
3. Other NEs automatically function as clients and send TCP connection requests to the server.
4. After receiving the TCP connection request from a client, the server establishes the corresponding TCP connection.
5. The NEs use the TCP connection as a MAC connection to realize ECC communication.
The implementation principle of the manual ECC extension is basically the same as that of the automatic ECC extension. The difference is that in the manual mode, the server, clients, and connection port numbers are manually specified.
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