Contents

Configuring BIER OAM·· 1

About BIER OAM·· 1

BIER OAM packet format 1

BIER ping· 3

BIER tracert 4

Enabling BIER OAM·· 7

Performing BIER ping· 8

Performing BIER tracert 8

 

Configuring BIER OAM

About BIER OAM

BIER Operation, Administration, and Maintenance (OAM) uses ping and tracert utilities to test BIER network connectivity.

·     BIER ping—Tests the reachability of destinations on a BIER network.

·     BIER tracert—Tests the reachability of destinations on a BIER network and identifies the fault point on the BIER forwarding path.

BIER ping and tracert add three headers: a UDP header, an IPv6 header, and an IPv6 BIER header in sequence to an OAM echo request or reply and transmit it over a BIER tunnel.

BIER OAM uses a UDP port number (default 49100) to listen and receive request packets. Upon receipt of a request, the destination responses with a UDP packet.

BIER OAM packet format

BIER ping and tracert use BIER OAM echo requests and replies for network diagnosis.

G-BIER echo packet format

Figure 1 shows the format of a G-BIER echo request or reply packet.

Figure 1 BIER OAM echo request/reply packet format

 

BIERv6 echo packet format

Figure 2 shows the format of a BIERv6 echo request or reply packet.

Figure 2 BIERv6 OAM echo request/reply packet format

 

MSR6 echo packet format

Figure 2 shows the format of an MSR6 echo request or reply packet.

Figure 3 BIERv6 OAM echo request/reply packet format

 

BIER OAM packet fields

The following describes the meanings of BIER OAM packet fields:

·     G-BIER/BIERv6/MSR6 header: For detailed information about the fields in the G-BIER, BIERv6, and MSR6 headers, see BIER Configuration Guide.

·     IPv6 header:

¡     Source Address—IPv6 source address, 32 bits in length. In a request packet, the value of this field is consistent with that in the BIER header. In a reply packet, the value of this field is the prefix of the destination BFR.

¡     Destination Address—IPv6 destination address, 32 bits in length. In a request packet, the value of this field is fixed at 0:0:0:0:0:FFFF:7F00:1. In a reply packet, the value of this field is the source IPv6 address of the request.

·     UDP header:

¡     Source Port—UDP source port number, 16 bits in length.

¡     Destination Port—UDP destination port number, 16 bits in length.

¡     UDP Length—UDP datagram length, 16 bits in length.

¡     UDP Checksum—UDP checksum, 16 bits in length. It is used to verify the integrity of the transmitted data.

BIER ping

BIER ping tests routing underlay connectivity and can be performed only if the BIER routing underlay is established. It does not rely on any BIER-based multicast service configuration or the IPv6 source address that represents the MSID, Src.DT4, or Src.DT6.

A node in a BIER domain transmits a BIER echo request packet to the destination BFER to initiate a ping test. After receiving the request packet, the destination BFER responds with a BIER echo reply packet. If the initiating node does not receive a response from the destination BFER node within the specified time, a timeout message is generated.

Figure 4 shows a BIER ping procedure. In this example, the packet is transmitted over the Device A→Device B→Device C→Device D path. For simplified illustration, the BSL used is 4 bits.

Figure 4 BIER ping

 

1.     Device A determines the BIER triplet information (BSL, sub-domain, and SI) based on the ping command and identifies the BIFT ID, 0x30100 in this example.

2.     Device A looks up the local BIER forwarding table based on the BIFT ID.

3.     Device A transmits the BIER echo request to Device B. Within the BIER header, the destination IPv6 address depends on the encapsulation type:

¡     For G-BIER, the destination IPv6 address is Device B's MPRA.

¡     For BIERv6, the destination IPv6 address is the End.BIER SID.

¡     For MSR6, the destination IPv6 address is the End.RGB SID.

4.     Device B looks up the local BIER forwarding table and then forwards the packet to Device C.

5.     Device C looks up the local BIER forwarding table and then forwards the packet to Device D.

6.     Upon receipt of the echo request, Device D which is the destination node returns an echo reply packet to Device A.

7.     Upon receiving the echo reply, Device A compares the key fields of the reply packet with those of the request packet it sent. If the fields match, Device A outputs the length, sequence number of response time of the reply packet. If the fields do not match, Device A ignores the packet.

8.     If Device A does not receive a response from the specified destination node within the specified waiting time, it outputs a timeout message.

BIER tracert

The BIER tracert uses the following process:

1.     The source node sends BIER echo requests.

The source node sends the first echo packet with a TTL of 1 and increments the TTL by 1 on each subsequent transmission, until the destination responds or until the maximum TTL is reached.

2.     Intermediate nodes processes the requests.

¡     After receiving an echo request, an intermediate node forwards the request if the TTL is not decremented to 0.

¡     If the TTL decrements to 0, it returns code 5 (successful packet forwarding) if a forwarding entry exists and code 8 (no matching entry in the forwarding table) if no matching entry exists in the forwarding table.

3.     Destination nodes respond with a BIER echo reply.

Upon receipt of an echo request, a destination node returns either of the following codes:

¡     3 (Replying BFR is the only BFER in header Bitstring)—The destination node is the only BFER matching the bit string in the BIER OAM echo request header.

¡     4 (Replying BFR is one of the BFER in header Bitstring)—The destination node is one of the BFERs matching the bit string in the BIER OAM echo request header.

A BFER will not be tested after it replies. The BIER tracert procedure is completed and BIER forwarding path information is provided only if all destination BFERs return code 3 or 4 or the maximum TTL is reached.

The subsections use the first, the second, and the last tracert round trips as examples to describe the BIER tracert procedure.

First tracert round trip

The TTL is 1 for the first tracert round trip, as shown in Figure 5.

Figure 5 First tracert round trip

 

1.     Device A determines the BIER triplet information (BSL, sub-domain, and SI) based on the tracert command and identifies the BIFT ID.

2.     Device A looks up the local BIER forwarding table based on the BIFT ID.

3.     Device A transmits the BIER echo request to Device B. Within the BIER header, the destination IPv6 address depends on the encapsulation type:

¡     For G-BIER, the destination IPv6 address is Device B's MPRA.

¡     For BIERv6, the destination IPv6 address is the End.BIER SID.

¡     For MSR6, the destination IPv6 address is the End.RGB SID.

The BFR prefix of Device B is carried in the Downstream Mapping TLV field.

4.     After the request arrives at Device B, its TTL is decremented to 0, and Device B returns an echo reply packet to Device A. Because Device B is a transit node, the echo reply packet carries its own BFR prefix in the Responder BFR TLV and the BFR prefixes of downstream Device C and Device E in the Downstream Mapping TLV.

5.     Upon receipt of the echo reply, Device A compares key fields in the reply with those in the request it sent. If the fields do not match, Device A ignores the reply. If the fields match, Device A displays reply information.

Second tracert round trip

The TTL is 2 for the second tracert round trip, as shown in Figure 6.

Figure 6 Second tracert round trip

 

1.     Device A looks up the local BIER forwarding table based on the BIFT ID.

2.     Device A transmits the BIER echo request to Device B. Within the BIER header, the destination IPv6 address depends on the encapsulation type:

¡     For G-BIER, the destination IPv6 address is Device B's MPRA.

¡     For BIERv6, the destination IPv6 address is the End.BIER SID.

¡     For MSR6, the destination IPv6 address is the End.RGB SID.

The BFR prefixes (copied from the received echo reply) of Device C and Device E are carried in the Downstream Mapping TLV field.

3.     After the request arrives at Device B, its TTL is decremented to 1.

4.     Device B looks up the local BIFT and forwards the packet to Device C.

5.     After the request arrives at Device C, its TTL is decremented to 0, and Device C returns an echo reply packet to Device A. Because Device C is a transit node, the echo reply packet carries its own BFR prefix in the Responder BFR TLV and the BFR prefix of downstream Device D in the Downstream Mapping TLV.

6.     Upon receipt of the echo reply, Device A compares key fields in the reply with those in the sent request. If the fields do not match, Device A ignores the reply. If the fields match, Device A displays reply information.

Last tracert round trip

The TTL is 3 for the last tracert round trip, as shown in Figure 6.

Figure 7 Second tracert round trip

 

1.     Device A looks up the local BIER forwarding table based on the BIFT ID.

2.     Device A transmits the BIER echo request to Device B. Within the BIER header, the destination IPv6 address depends on the encapsulation type:

¡     For G-BIER, the destination IPv6 address is Device B's MPRA.

¡     For BIERv6, the destination IPv6 address is the End.BIER SID.

¡     For MSR6, the destination IPv6 address is the End.RGB SID.

The BFR prefixes (copied from the received echo reply) of Device C and Device E are carried in the Downstream Mapping TLV field.

3.     After the request arrives at Device B, its TTL is decremented to 2, and Device B looks up the local BIFT and forwards the packet to Device C.

4.     After the request arrives at Device C, its TTL is decremented to 1, and Device C looks up the local BIFT and forwards the packet to Device D.

5.     After the request arrives at Device D, its TTL is decremented to 0, and Device D returns an echo reply packet to Device A. Because Device D is a destination node, the echo reply packet carries its own BFR prefix in the Responder BFR TLV and does not carry the Responder BFR TLV.

6.     Upon receipt of the echo reply, Device A compares key fields in the reply with those in the sent request. If the fields do not match, Device A ignores the reply. If the fields match, Device A displays reply information.

Enabling BIER OAM

Restrictions and guidelines

Devices transmit BIER OAM packets over UDP. To avoid UDP port conflict between BIER OAM and other protocols, use the default UDP port number for BIER OAM packets.

For BFRs in a BIER sub-domain to receive BIER echo requests, specify the same UDP port number for the BFRs.

Procedure

To enable BIER OAM, execute the following command:

bier ipv6 oam enable [ udp-port udp-port ]

By default, BIER OAM is enabled.

Performing BIER ping

Restrictions and guidelines

Before configuring this task, make sure BIER OAM is enabled.

If you specify multiple destination BFRs in this command, make sure all the BFRs are in the same SI.

After sending a BIER echo request, the device waits for the response timeout to expire before a subsequent transmission if the specified echo request transmission interval is less than the response timeout.

Procedure

To test reachability of one or a range of BFRs on the BIER network, execute the following command in any view:

ping bier { bierv6 | g-bier | msr6 } sub-domain sub-domain-id bsl bsl-value  bfr-id bfr-id-value [ to bfr-id-end-value ] [ -c count | -h ttl-value | -m interval | -t timeout | udp-port udp-port ] *

Performing BIER tracert

Restrictions and guidelines

Before configuring this task, make sure BIER OAM is enabled.

After a fault is detected by using the ping bier command, you can use the tracert bier command to locate the fault point on the network.

If multiple BIER ECMP paths exist between the source node and destination node, specify an entropy value for selection of a path.

Procedure

To trace the path that a BIER packet traverses from the source to destination, execute the following command in any view:

tracert bier { bierv6 | g-bier | msr6 } sub-domain sub-domain-id bsl bsl-value bfr-id bfr-id-value [ to bfr-id-end-value ] [ entropy entropy-value [ to entropy-end-value ] | -ds | -h ttl-value | -ibs | -t timeout | -tbs | udp-port udp-port ] *