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ME60 V800R010C10SPC500 Feature Description - WAN Access 01

This is ME60 V800R010C10SPC500 Feature Description - WAN Access
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BGP-LS

BGP-LS

BGP-link state (LS) enables BGP to report topology information collected by IGPs to the controller.

Background

BGP-LS is a new method of collecting topology information.

Without BGP-LS, the ME device uses an IGP (OSPF or IS-IS) to collect topology information of each AS, and the IGP reports the information to the controller. This topology information collection method has the following disadvantages:
  • The controller must have high computing capabilities and support the IGP and its algorithm.
  • The controller cannot gain the complete inter-AS topology information and therefore is unable to calculate optimal E2E paths.
  • Different IGPs report topology information separately to the controller, which complicates the controller's analysis and processing.

For details on how OSPF collects topology information, see ME60 Feature Description - OSPF.

For details on how IS-IS collects topology information, see ME60 Feature Description - IS-IS.

With powerful routing capabilities of BGP, BGP-LS has the following advantages:
  • Reduces computing capability requirements and spares the necessity of IGPs on the controller.
  • Facilitates route selection and calculation on the controller by using BGP to summarize process or AS topology information and report the complete information to the controller.
  • Requires only one routing protocol (BGP) to report topology information to the controller.

Related Concepts

BGP-LS provides a simple and efficient method of collecting topology information.

BGP-LS routes carry topology information and are classified into three types of routes that carry node, link, and route prefix information, respectively. Theses routes collaborate in carrying topology information.

BGP-LS Route Formats

Format of node routes

For example, a node route is in the format of [NODE][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as100][bgp-ls-identifier11.1.1.2][ospf-area-id0.0.0.0][igp-router-id0000.0000.0001.00]].

Node routes carry node information.

Table 9-7 describes the fields in node routes.

Table 9-7 Description of the fields in node routes

Item

Description

NODE

Field indicating that the BGP-LS route is a node route.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

Format of link routes

For example, a link route is in the format of [LINK][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as255.255][bgp-ls-identifier192.168.102.4][ospf-area-id0.0.0.0][igp-router-id0000.0000.0002.01]][REMOTE[as255.255][bgp-ls-identifier192.168.102.4][ospf-area-id0.0.0.0][igp-router-id0000.0000.0002.00]][LINK[if-address0.0.0.0][peer-address0.0.0.0][if-address::][peer-address::][mt-id0]].

Link routes carry information about links between devices.

Table 9-8 describes the fields in link routes.

Table 9-8 Description of the fields in link routes

Item

Description

LINK

Field indicating that the BGP-LS route is a link route.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

REMOTE

Field indicating information of a remote node.

if-address

IP address of the local interface.

peer-address

IP address of the remote interface.

mt-id

ID of the topology.

Format of prefix routes

For example, a prefix route is in the format of [IPV4-PREFIX][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as100][bgp-ls-identifier192.168.102.3][ospf-area-id0.0.0.0][igp-router-id0000.0000.0001.00]][PREFIX[mt-id0][ospf-route-type0][prefix192.168.102.0/24]].

Prefix routes carry information about reachable network segments.

Table 9-9 describes the fields in link routes.

Table 9-9 Description of the fields in prefix routes

Item

Description

IPV4-PREFIX

Field indicating an IPv4 or IPv6 prefix route. The ME device cannot generate IPv6 prefix routes, but it can process the IPv6 prefix routes received from non-Huawei devices.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

PREFIX

Field indicating an IGP route.

mt-id

ID of the topology.

ospf-route-type

OSPF route type:
  • 1: Intra-Area
  • 2: Inter-Area
  • 3: External 1
  • 4: External 2
  • 5: NSSA 1
  • 6: NSSA 2
prefix

Prefix of an IGP route.

Typical Networking

Networking in which topology information is collected within an IGP area

In Figure 9-42, Device A, Device B, Device C, and Device D use IS-IS to communicate with each other at the network layer. They are all Level-2 devices in the same area (area 10). Only one of the four devices needs to have BGP-LS deployed and establish a BGP-LS peer relationship with the controller so that BGP-LS can collect and report topology information to the controller. To improve reliability, deploying BGP-LS on two or more devices and establishing a BGP-LS peer relationship between each BGP-LS device and the controller are recommended. The BGP-LS devices collect the same topology information, and they back up each other in case one of them fails.

Figure 9-42 Networking in which topology information is collected within an IGP area

Networking in which topology information is collected between IGP areas

In Figure 9-43, Device A, Device B, Device C, and Device D use IS-IS to communicate with each other at the network layer. Device A, Device B, and Device C reside in area 10, whereas Device D resides in area 20. Device A and Device B are Level-1 devices, Device C is a Level-1-2 device, and Device D is a Level-2 device. Only one of the four devices needs to have BGP-LS deployed and establish a BGP-LS peer relationship with the controller so that BGP-LS can collect and report topology information to the controller. To improve reliability, deploying BGP-LS on two or more devices and establishing a BGP-LS peer relationship between each BGP-LS device and the controller are recommended. The BGP-LS devices collect the same topology information, and they back up each other in case one of them fails.

Figure 9-43 Networking in which topology information is collected between IGP areas

Networking in which topology information is collected between BGP ASs

In Figure 9-44, Device A and Device B belong to the same AS, and an IS-IS neighbor relationship is established between them. BGP is not enabled on Device A. An EBGP peer relationship is established between Device B and Device C. If BGP-LS is not enabled, BGP cannot exchange topology information between AS 100 and AS 200. As a result, the topology information collected in AS 100 is different from that collected in AS 200. To address this problem, enable BGP-LS on at least one device (two or more is recommended for higher reliability) in each AS and establish a BGP-LS peer relationship between each of the devices and the controller.

Figure 9-44 Networking 1 in which topology information is collected between BGP ASs

If two controllers are deployed and are connected to different ASs, for example in Figure 9-45, a BGP-LS peer relationship must be established between the two controllers or between Device B and Device C so that both controllers can obtain topology information on the whole network.

Figure 9-45 Networking 2 in which topology information is collected between BGP ASs
NOTE:

To reduce the number of connections to the controller, deploy one or more BGP-LS RRs and establish BGP-LS peer relationships between each RR and the devices that require BGP-LS peer relationships with the controller.

Usage Scenario

The ME device functions as a forwarder and reports topology information to the controller for topology monitoring and traffic control.

Benefits

BGP-LS offers the following benefits:

  • Reduces computing capability requirements of the controller.
  • Allows the controller to gain the complete inter-AS topology information.
  • Requires only one routing protocol (BGP) to report topology information to the controller.
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Updated: 2019-01-04

Document ID: EDOC1100059473

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