Segunda instancia

When an Ethernet port works in a fixed working mode, use non-auto-negotiation flow control.

The non-auto-negotiation flow control modes include the following:

l Send only

The port can transmit PAUSE frames in case of congestion but cannot process received PAUSE frames.

l Receive only

The port can process received PAUSE frames but cannot transmit PAUSE frames in case of congestion.

l Symmetric

The port can transmit PAUSE frames and can also process received PAUSE frames.

l Disabled

The port does not transmit or process PAUSE frames.

NOTE

On the NMS, the OptiX RTN 950 supports only two non-auto-negotiation flow control modes: Disabled mode and Enable Symmetric Flow Control (symmetric) mode.

7 Configuring Networkwide Service Data

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7.1.12 MAC Address Table Management

The entries in a MAC address table show the mappings between MAC addresses and ports. A MAC address table contains dynamic entries, static entries, and blacklist entries.

l Dynamic entry

A dynamic entry is obtained by learning of a bridge through the SVL/IVL mode. The dynamic entry will be aged.

l Static entry

A static entry is manually added to the MAC address table by a network administrator using the NMS. The static entry will not be aged. Generally, the static entry is configured for a port if a device with a known MAC address is mounted to the port and this device transmits large traffic for a long time.

l Blacklist entry

A blacklist entry is a MAC disabled entry and is used to discard a data frame that contains a specified MAC address (source MAC address or destination MAC address). A blacklist entry is also called a blackhole entry. The blacklist entry is configured by the network administrator. The blacklist entry does not age, and is not lost after the Ethernet processing board is reset.

NOTE

A routing entry is automatically deleted when that routing entry is not updated within a specified period.

This occurs when no new packet from this MAC address is received to enable the re-learning of this MAC address. This mechanism is called aging, and this period is called aging time.

7.1.13 Split Horizon Group

To separate services that are converged and to prevent a broadcast storm resulting from a service loop, you can configure a split horizon group for the E-LAN services at the specified nodes.

After the configuration, the logical ports in one split horizon group cannot forward packets to each other.

Figure 7-7 shows a typical application of the split horizon group. NEs on the network are configured with E-LAN services, and the east and west ports and service access ports are configured as mounted ports of a bridge. In this case, if a split horizon group is not configured at NE1, broadcast storm occurs due to a network loop as the east and west ports can forward packets to each other. If a split horizon group is created at NE1 and the east and west ports are configured as members of the split horizon group, the east and west ports do not forward packets to each other. Therefore, a service loop is prevented.

Figure 7-7 Split horizon group

l ERPS can prevent a service loop on a ring network. If ERPS is already enabled for a ring network, a split horizon group is not needed as it may affect ERPS operation.

l On the OptiX RTN 950, only the split horizon group configuration based on physical ports is supported.

Therefore, if a physical port is mapped into several logical ports and one of these logical ports is a member of a split horizon group, the other logical ports are added to the split horizon group automatically.

7.1.14 Protection for Native Ethernet Services

The OptiX RTN 950 supports three protection modes for Native Ethernet services, namely, Ethernet ring protection switching (ERPS), link aggregation group (LAG), and multiple spanning tree protocol (MSTP).

ERPS

ERPS is applicable to ring physical networks and can provide protection for the E-LAN services between all the nodes on the ring network. Generally, when a ring network is configured with ERPS, the RPL node blocks the RPL port on one side so that all the services are transmitted through the ports on the other side. In this manner, service loops are prevented. If a section of link fails or an NE becomes faulty, the RPL node unblocks its RPL port so that the services are switched from the faulty point to the RPL port for transmission. In this manner, protection for the ring network is achieved.

The Ethernet ring network shown in Figure 7-8 is configured with ERPS. Generally, the RPL node (NE D) blocks its RPL port that is connected to NE A, and all the services are transmitted over the link NE A <-> NE B <-> NE C <-> NE D. When the link between NE A <-> NE B becomes faulty, NE D unblocks the blocked port so that the services can be transmitted over the link NE A <-> NE D <-> NE C <-> NE B.

7 Configuring Networkwide Service Data

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Figure 7-8 Implementation of ERPS

Protection switching

Link NE B

NE A

NE C

NE D

NE B

NE A

NE C

NE D Failure

Ethernet service direction Blocked port

The LAG provides users with a cost-effective method for increasing link bandwidth. The users obtain data links with higher bandwidths by combining multiple physical links into one logical link without upgrading the existing equipment. The bandwidth of the logical link is equal to the sum of the bandwidths of the physical links. The aggregation module distributes the traffic to different members by using the load balancing algorithm, achieving the load balancing at the link level.

l Improved the link availability

The links in a LAG provide backup for each other dynamically. When a link fails, another link in the LAG quickly takes over. This process in which link aggregation starts the backup link only applies to the links in the same LAG and it cannot be performed on links that are not in the LAG.

The OptiX RTN 950 supports only the MSTP protocol that uses the common and internal spanning tree (CIST). The MSTP that uses the CIST can be used as a rapid spanning tree protocol (RSTP). The RSTP is applicable in case of a network loop. This protocol adopts certain algorithms to reconstruct a loop network into a loop-free tree network and therefore prevents Ethernet frames from increasing and cycling in an endless manner on the loop network.

On the OptiX RTN 950, the MSTP is used to prevent a network loop on the access side.

See Figure 7-10. When the user equipment is connected to the OptiX RTN 950 through two different trails, you can configure the ports on the OptiX RTN 950 that are connected to the user network into a port group. This port group, together with the switch on the user network, can run the MSTP. If a service access link becomes faulty, the MSTP enables a re-configuration to generate the spanning tree topology, providing protection for the user network that is configured with multiple access points.

7 Configuring Networkwide Service Data

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Figure 7-10 Prevention of network loops on the access side

CIST

Root Root

Port group

Blocked Port

7.1.15 Clock Source

A clock source is a signal source that carries timing reference information. An NE implements clock synchronization, by using its phase locked loop (PLL) to lock the timing information of the clock source.

The OptiX RTN 950 supports the following clock sources:

l Radio clock source: refers to a clock source that is extracted from the received radio signal.

l Ethernet clock source: refers to a clock source that is extracted from the Ethernet stream.

l Internal clock source: refers to a clock source that is generated through the free-run oscillation of an NE built-in clock. The internal clock source has the lowest priority.

7.1.16 Clock Protection Modes

The OptiX RTN 950 supports clock source protection based on priorities, synchronization status message (SSM) protection, and extended SSM protection.