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NE20E-S V800R010C10SPC500 Feature Description - Interface and Data Link 01

This is NE20E-S V800R010C10SPC500 Feature Description - Interface and Data Link

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Basic Concepts

Basic Concepts

Interface Types

The router exchanges data and interacts with other devices on a network through interfaces. Interfaces are classified into physical and logical interfaces.

  • Physical Interfaces

    Physical interfaces physically exist on boards. They are divided into the following types:

    • LAN interfaces: interfaces through which the router can exchange data with the devices on a LAN.
    • WAN interfaces: interfaces through which the router can exchange data with remote devices on a WAN.
  • Logical Interfaces

    Logical interfaces are manually configured interfaces that do not exist physically. Logical interfaces can be used to exchange data.

Interface Numbering Rules

For details, see Hardware Description > Boards > Overview > Rules for Numbering Slots and Interfaces.

Interface Views and Prompts

The NE20E supports the command views and prompts of physical interfaces in Table 2-1 and the command views and prompts of logical interfaces in Table 2-2.
Table 2-1 Command views and prompts of physical interfaces supported by the NE20E

Interface Name

Command View

Accessing Command

Prompt

Ethernet interface

Ethernet interface view

Run the interface ethernet 0/1/0 command in the system view.

[~HUAWEI-Ethernet0/1/0]

GE interface

GE interface view

Run the interface gigabitethernet 0/1/0 command in the system view

[~HUAWEI-GigabitEthernet0/1/0]

10GE interface

10GE interface view

Run the interface 10GE 0/1/0 command in the system view

[~HUAWEI-10GE0/1/0]

40GE interface

40GE interface view

Run the interface 40GE 0/1/0 command in the system view

[~HUAWEI-40GE0/1/0]

100GE interface

100GE interface view

Run the interface 100GE 0/1/0 command in the system view

[~HUAWEI-100GE0/1/0]

POS interface

POS interface view

Run the interface pos 0/3/0 command in the system view

[~HUAWEI-Pos0/3/0]

50GE interface

50GE interface view

Run the interface 50GE 0/1/0 command in the system view.

[~HUAWEI-50GE0/1/0]

50|100GE interface

50|100GE interface view

Run the interface 50|100GE 0/1/0 command in the system view.

[~HUAWEI-50|100GE0/1/0]

FlexE-50G interface

FlexE-50G interface view

Run the interface FlexE-50G 0/1/0 command in the system view.

[~HUAWEI-FlexE-50G0/1/0]

FlexE-50|100G interface

FlexE-50|100G interface view

Run the interface FlexE-50|100G 0/1/0 command in the system view.

[~HUAWEI-FlexE-50|100G0/1/0]

Table 2-2 Command views and prompts of logical interfaces

Interface Name

Command View

Accessing Command

Prompt

Sub-interface

Sub-interface view

Run the interface gigabitethernet 0/1/0.1 command in the system view

[~HUAWEI-GigabitEthernet0/1/0.1]

Eth-Trunk interface

Eth-Trunk interface view

Run the interface eth-trunk 0 command in the system view

[~HUAWEI-Eth-Trunk0]

Loopback interface

Loopback interface view

Run the interface loopback 2 command in the system view

[~HUAWEI-LoopBack2]

Null interface

Null interface view

Run the interface null 0 command in the system view

[~HUAWEI-NULL0]

IP-Trunk interface

IP-Trunk interface view

Run the interface ip-trunk 0 command in the system view

[~HUAWEI-Ip-Trunk0]

Tunnel interface

Tunnel interface view

Run the interface tunnel 0/1/0 command in the system view

[~HUAWEI-Tunnel0/1/0]

FlexE interface

FlexE interface view

Run the interface FlexE 0/9/129 command in the system view.

[~HUAWEI-FlexE0/9/129 ]

Commonly-used Link Protocols and Access Technologies

The link layer is responsible for accurately sending data from a node to a neighboring node. It receives packets from the network layer, encapsulates the packets in frames, and then sends the frames to the physical layer.

Major link layer protocols supported by the NE20E are listed as follows:

  • Ethernet

    Currently, the LAN mostly refers to the Ethernet. The Ethernet is a broadcast network, which is flexible and simple in configuration and is easy to expand. The Ethernet is widely used.

  • Trunk

    Trunks can be classified into Eth-Trunks and IP-Trunks. An Eth-Trunk must be composed of Ethernet links, and an IP-Trunk must be composed of POS links.

    The trunk technology has the following advantages:

    • Bandwidth increase: The bandwidth of an IP-Trunk is the total bandwidth of all member interfaces.
    • Reliability enhancement: When a link fails, other links in the same trunk automatically take over the services on the faulty link to prevent traffic interruption.
  • PPP

    The Point-to-Point Protocol (PPP) is used to encapsulate IP packets on serial links. It supports both the asynchronous transmission of 8-bit data without the parity check and the bit-oriented synchronous connection.

    PPP consists of the Link Control Protocol (LCP) and the Network Control Protocol (NCP). LCP is used to create, configure, and test links; NCP is used to control different network layer protocols.

  • HDLC

    The High-Level Data Link Control (HDLC) is a suite of protocols that are used to transmit data between network nodes. HDLC is widely used at the data link layer.

    In HDLC, the receiver responds with an acknowledgement when it receives frames transmitted over the network. In addition, HDLC manages data flows and the interval at which data packets are transmitted.

MTU

The maximum transmission unit (MTU) is the size (in bytes) of the longest packet that can be transmitted on a physical network. The MTU is very important for interworking between two devices on a network. If the size of a packet exceeds the MTU supported by a transit node or a receiver, the transit node or receiver may fragment the packet before forwarding it or may even discard it, increasing the network transmission loads. MTU values must be correctly negotiated between devices to ensure that packets reach the receiver.

  • If fragmentation is disallowed, packet loss may occur during data transmission at the IP layer. To ensure that long packets are not discarded during transmission, configure forcible fragmentation for long packets.

  • When an interface with a small MTU receives long packets, the packets have to be fragmented. Consequently, when the quality of service (QoS) queue becomes full, some packets may be discarded.

  • If an interface has a large MTU, packets may be transmitted at a low speed.

Control-Flap

The status of an interface on a device may alternate between Up and Down for various reasons, including physical signal interference and incorrect link layer configurations. The changing status causes Multiprotocol Label Switching (MPLS) and routing protocols to flap. As a result, the device may break down, causing network interruption. Control-flap controls the frequency of interface status alternations between Up and Down to minimize the impact on device and network stability.

The following two control modes are available.

Table 2-3 Flapping control modes

Control Mode

Function

Usage Scenario

control-flap

Controls the frequent flappings of interfaces from the network layer to minimize the impact on device and network stability.

  • This control mode is interface-specific.
  • This control mode suppresses interface flappings from the network layer and reports the flappings to the routing management module, thereby improving network-layer stability.
  • This control mode allows you to precisely configure parameters based on service requirements.
  • This control mode involves complex algorithms and is highly demanding to use.

damp-interface

Controls the frequent flappings of interfaces at the physical layer to minimize the impact on device and network stability.

  • This function is supported globally or on a specified interface.
  • This control mode suppresses the flappings from the physical layer, thereby improving link-layer and network-layer stability.
  • This control mode prevents the upper-layer protocols from frequently alternating between enabled and disabled, thereby reducing the consumption of CPU and memory resources.
  • This control mode does not involve any complex algorithms and is easy to use.
  • control-flap

    Concepts of control-flap:

    • Penalty value and threshold

      An interface is suppressed or freed from suppression based on the penalty value.

      • Penalty value: This value is calculated based on the status of the interface using the suppression algorithm. The penalty value increases with the changing times of the interface status and decreases with the half life.
      • Suppression threshold (suppress): The interface is suppressed when the penalty value is greater than the suppression threshold.
      • Reuse threshold (reuse): The interface is no longer suppressed when the penalty value is smaller than the reuse threshold.
      • Ceiling threshold (ceiling): The penalty value no longer increases when the penalty value reaches the ceiling threshold.

      The parameter configuration complies with the following rule: reuse threshold (reuse) < suppression threshold (suppress) < maximum penalty value (ceiling).

    • Half life

      When an interface goes Down for the first time, the half life starts. A device matches against the half life based on the actual interface status. If a specific half life is reached, the penalty value decreases by half. Once a half life ends, another half life starts.

      • Half life when an interface is Up (decay-ok): When the interface is Up, if the period since the end of the previous half life reaches the current half life, the penalty value decreases by half.
      • Half life when an interface is Down (decay-ng): When the interface is Down, if the period since the end of the previous half life reaches the current half life, the penalty value decreases by half.
    • Maximum suppression time: The maximum suppression time of an interface is 30 minutes. When the period during which an interface is suppressed reaches the maximum suppression time, the interface is automatically freed from suppression.
    • Penalty value: This value is calculated based on the status of the interface using the suppression algorithm. The core of the suppression algorithm is that the penalty value increases with the changing times of the interface status and decreases exponentially.
    • Suppression threshold: The interface is suppressed when the penalty value is greater than the suppression threshold. The suppression threshold must be greater than the reuse threshold and smaller than the ceiling threshold.
    • Reuse threshold: The interface is no longer suppressed when the penalty value is smaller than the reuse threshold. The reuse threshold must be smaller than the suppression threshold.
    • Ceiling threshold: The penalty value no longer increases when the penalty value reaches the ceiling threshold. The ceiling threshold must be greater than the suppression threshold.

    You can set the preceding parameters on the NE20E to restrict the frequency at which an interface can alternate between Up and Down.

    Principles of interface flapping control:

    In Figure 2-1, the default penalty value of an interface is 0. The penalty value increases by 400 each time the interface goes Down. When an interface goes Down for the first time, the half life starts. The system checks whether the specific half life expires at an interval of 1s. If the specific half life expires, the penalty value decreases by half. Once a half life ends, another half life starts.

    • If the penalty value exceeds the interface suppressing threshold, the interface is suppressed. When the interface is suppressed, the outputs of the display interface, display interface brief, and display ip interface brief commands show that the protocol status of the interface remains DOWN(dampening suppressed) and does not change with the physical status.

    • If the penalty value falls below the interface reuse threshold, the interface is freed from suppression. When the interface is freed from suppression, the protocol status of the interface is in compliance with the actual status and does not remain Down (dampening suppressed).

    • If the penalty value reaches ceiling, the penalty value no longer increases.

    Figure 2-1 Flapping control

  • damp-interface

    Related concepts:

    • penalty value: a value calculated by a suppression algorithm based on an interface's flappings. The suppression algorithm increases the penalty value by a specific value each time an interface goes Down and decreases the penalty value exponentially each time the interface goes Up.
    • suppress: An interface is suppressed if the interface's penalty value is greater than the suppress value.
    • reuse: An interface is no longer suppressed if the interface's penalty value is less than the reuse value.
    • ceiling: calculated using the formula of reuse x 2 (MaxSuppressTime/HalfLifeTime). ceiling is the maximum penalty value. An interface's penalty value no longer increases when it reaches ceiling.
    • half-life-period: period that the penalty value takes to decrease to half. A half-life-period begins to elapse when an interface goes Down for the first time. If a half-life-period elapses, the penalty value decreases to half, and another half-life-period begins.
    • max-suppress-time: maximum period during which an interface's status is suppressed. After max-suppress-time elapses, the interface's actual status is reported to upper layer services.

    Figure 2-2 shows the relationship between the preceding parameters. To facilitate understanding, figures in Figure 2-2 are all multiplied by 1000.

    Figure 2-2 Suppression on physical interface flappings

    At t1, an interface goes Down, and its penalty value increases by 1000. Then, the interface goes Up, and its penalty value decreases exponentially based on the half-life rule. At t2, the interface goes Down again, and its penalty value increases by 1000, reaching 1600, which has exceeded the suppress value 1500. At this time if the interface goes Up again, its status is suppressed. As the interface keeps flapping, its penalty value keeps increasing until it reaches the ceiling value 10000 at tA. As time goes by, the penalty value decreases and reaches the reuse value 750 at tB. The interface status is then no longer suppressed.

NOTE:

Loopback, Layer 2 interfaces that are converted from Layer 3 interfaces using the portswitch command and NULL interfaces do not support setting the maximum transmission unit (MTU) and deploying control-flap.

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Updated: 2019-01-03

Document ID: EDOC1100055118

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