NE05 in a site connects to the equipment of C company through POS port, and the link layer is encapsulated with HDLC protocol. NE05 is replaced with NE40, after which the link layer is up but the protocol is down, so interconnection fails. Services are restored by cutover to NE05.
1. Protocols for link layer of two POS ports are HDLC, and both fail to interconnect after HDLC at link layer of both POS port is replaced with PPP.
2. POS port of NE40 has a loop; in either PPP or HDLC mode, the port has traffic, so the hardware of unit is normal.
3. Both POS ports use scramble, and physical layer is encapsulated to SDH.
4. According to the configuration of NE05 before cutover and the current configurations of NE40 on network, and configuration of POS port of C7609, only CRC of both sides is found different. CRCs of both NE05 and C7609 are all 16-bit, and that of NE40 is 32-bit. Because of difference in configuration of CRC of both NE40 and C7609, NE40 fails to interconnect with POS port of C7609.
5. The CRC of POS port of NE40 is 32-bit, and cannot be changed, so after the CRC of POS of C7609 to 32-bit, they could interconnect normally.
1. Link layer protocols for POS ports of both sides differ.
2. The methods for scramble of two POS ports differ.
3. Encapsulations of physical layer of POS ports differ.
4. POS port of NE40 is problematic.
By default, the configuration of POS of NE40 differs to that of C equipment in most aspects, so it needs to change the relevant configurations for interconnection of POS ports; otherwise, protocol layer cannot be up.
1. POS link protocol
Equipment of C company uses HDLC as default link layer protocol, and NE40 uses PPP by default. Both equipment must be configured the same, or protocol layer of two POS ports at both sides cannot be up.
2. POS check
CRC of C company is defaulted to 16-bit, and NE40 is defaulted to 32-bit; the setting must be the same, or protocol layer for POS at both sides cannot be up.
Note: CRC of NE40 cannot be changed, so the only way for interconnection is to change the CRC of C equipment.
3. POS scramble
C company is defaulted to be non-scramble, but NE40 is defaulted to be so; they must be configured the same, or the protocol layer for POS at two sides cannot be up.
4. Encapsulation of physical layer of POS
The physical layer of equipment of C company is defaulted to encapsulate with SONET, but NE40 is defaulted to encapsulate with SDH. The difference in configurations here could be compatible, without influence on protocol layer and on forwarding. However, it is advisable to configure the encapsulation of physical layer to the same.