RRPP Technology White Paper

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RRPP Technology White Paper

Hangzhou H3C Technologies Co., Limited 1/30

RRPP Technology White PaperKeywords: RRPP, RRPP domain, RRPP ring, control VLAN, protected VLAN, master node,

transit node, edge node, assistant-edge node, ring group.

Abst ract: The Rapid Ring Protection Protocol (RRPP) is a link layer protocol dedicated to

Ethernet rings. This document introduces H3Cs RRPP implementation, characteristics,

and typical networking schemes.

Acronyms:Acronym Full spelling

RRPP Rapid Ring Protection Protocol

SRPT Sub Ring Packet Tunnel in Major Ring

STP Spanning Tree Protocol

VLAN Virtual Local Area Network


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Table of Contents

1 Overview........................................................................................................................................31.1 Background ........................................................................................................................31.2 Benefits ...............................................................................................................................3

2 RRPP Implementation ..................................................................................................................42.1 Basic Concepts in RRPP...................................................................................................4

2.1.1 RRPP Domain .........................................................................................................42.1.2 RRPP Ring...............................................................................................................52.1.3 RRPP Control VLAN ...............................................................................................62.1.4 RRPP Protected VLAN ...........................................................................................62.1.5 Master Node ............................................................................................................62.1.6 Transit Node ............................................................................................................72.1.7 Edge Node and Assistant-Edge Node ...................................................................82.1.8 Primary Port and Secondary Port ..........................................................................82.1.9 Common Port and Edge Port .................................................................................9

2.2 RRPPDUs...........................................................................................................................92.2.1 RRPPDU Types.......................................................................................................92.2.2 RRPPDU Format...................................................................................................11

2.3 Single Ring Fundamentals ..............................................................................................122.3.1 Single-Domain Single Ring...................................................................................122.3.2 Multi-Domain Single Ring .....................................................................................17

2.4 Intersecting Ring Fundamentals .....................................................................................182.4.1 Single-Domain Intersecting Rings........................................................................182.4.2 Multi-Domain Intersecting Rings ..........................................................................192.4.3 SRPT State Detection Mechanism ......................................................................20

3 Application Scenarios .................................................................................................................273.1 Single-Domain Single Ring .............................................................................................273.2 Multi-Domain Single Ring ................................................................................................273.3 Tangent Rings ..................................................................................................................283.4 Single-Domain Intersecting RRPP Rings.......................................................................293.5 Multi-Domain Intersecting RRPP Rings .........................................................................293.6 RRPP in Combination with STP......................................................................................30


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1 Overview1.1 Background

Nowadays, most networks use the ring structure to improve reliability. With ring

networking technologies, network devices are connected to form rings. To avoid

broadcast storms, which are common in a ring network, a loop protection mechanism

must be used.

The IEEE spanning tree protocols have been widely used for loop protection.

However, as STP topology convergence gets slower while network size is growing,transmission performance can be degraded in a large network.

To remove the negative impact of network size on topology convergence and shorten

topology convergence time, H3C developed RRPP.

1.2 BenefitsRRPP is a link layer protocol dedicated to Ethernet rings. It can prevent broadcast

storms caused by data loops when an Ethernet ring is healthy, and rapidly restore the

communication paths between the nodes after a link is disconnected on the ring by

bringing up the backup link.

Compared with STP, RRPP has the following advantages:z Fast topology convergence within 50 ms.

z Convergence time independent of Ethernet ring size.On intersecting rings, the topology change of an RRPP ring does not cause topology

changes in the other rings, and therefore, data transmission is more stable. In

addition, RRPP supports load sharing in Ethernet rings, which improves physical link

bandwidth utilization.


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2 RRPP Implementation2.1 Basic Concepts in RRPP2.1.1 RRPP Domain

An RRPP domain identified by an integral ID defines a topology range calculated and

controlled by the RRPP protocol. It consists of some interconnected devices with the

same domain ID, control VLANs, and protected VLANs. A device can belong to

multiple RRPP domains.

An RRPP domain consists of the following elements:z RRPP ringsz RRPP control VLANsz RRPP protected VLANsz Master nodesz Transit nodesz Edge nodes

z Assistant-edge nodes

In Figure 1, Domain 1 is an RRPP domain that contains Ring 1 and Ring 2 formed by

devices S1 through S6. Ring 1 is the primary ring, where S1 is the master node and

S2, S3, and S4 are transit nodes. Ring 2 is the subring, where S6 is the master node,

and S5 is a transit node. S3 and S2 are the edge node and the assistant-edge node

respectively. The primary control VLAN and secondary control VLAN of Domain 1 are

VLAN 3 and VLAN 4 respectively.


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S1

3

S2

S3S4

S5

S6

4

4

3 3

4

3 4

4 4

4

3 4

3 4 4

4 4

4 43 3

S

P

PS

Master

Edge

Assistant

Master

Ring 1 Ring 2

Domain 1

B

B

B

P - Primary Port

- Secondary Port

- Blocked Port

RRPP Domain Outline

Major Ctrl VLAN:3

Sub Ctrl VLAN:4

S

Figure 1A sample RRPP domain

2.1.2 RRPP RingEach RRPP ring corresponds to a ring-shaped Ethernet topology and is identified by

an integral ID. As described in the last section, an RRPP domain consists of a single

RRPP ring or multiple connected RRPP rings. The topology calculation is actually

based on RRPP rings.

Typically, ring topologies fall into these three types: single ring, tangent rings, and

intersecting rings. For each topology type, the RRPP domain configuration is different:

z All devices on the single ring are configured to be in the same RRPP domain.

z All devices on intersecting rings are also configured to be in the same RRPP

domain.

z For two tangent rings, the devices on each ring are configured to be in the same

RRPP domain. That is, two tangent rings need two different RRPP domains,

one for each ring.

In an RRPP domain with intersecting rings, to achieve independent topology

calculation on each ring without affecting other rings and prevent loops, you need to

configure one ring as the primary ring and the others as subrings. The primary ring as

a whole serves as a logical node on the subrings, and protocol packets from the


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subrings are transparently transmitted through the primary ring. In this way, topology

calculation is performed on the intersecting rings as a whole. Protocol packets of the

primary ring are confined within the primary ring. The level of the primary ring is 0 and

that of subrings is 1.

For example, to configure Ring 1 in Figure 1 as the primary ring, you should set its

ring level to 0 and set the level of all the other rings in the domain, Ring 2 in this

example, to 1. By doing this, you can prevent loops in the intersecting ring topology

and ensure the connectivity between nodes.

2.1.3 RRPP Control VLANAs described earlier, RRPP separates data traffic from RRPPDUs (RRPP packets) by

transmitting RRPPDUs in dedicated VLANs called control VLANs. An RRPP domain

is configured with one primary control VLAN and one secondary control VLAN. After

you specify a VLAN as the primary control VLAN, the VLAN whose ID is one plus the

primary control VLAN ID is configured as the secondary control VLAN automatically.

The primary control VLAN transmits the RRPPDUs of the primary ring and the EDGE-

HELLO messages of the subrings. The secondary control VLAN transmits the

RRPPDUs of the subrings except the EDGE-HELLO messages.

All the ports connecting devices to RRPP rings are assigned to control VLANs, and

only such ports can be assigned to control VLANs. As shown in Figure 1, 3 and/or 4

near a port indicate the VLAN(s) the port is assigned to. RRPP ports on the primary

ring must be assigned to both the primary control VLAN and the secondary control

VLAN; RRPP ports on the subrings can be assigned to only the secondary control

VLAN.

2.1.4 RRPP Protected VLAN

A protected VLAN is a VLAN that transmits data packets. It can contain both RRPP

ports and non-RRPP ports. A protected VLANs forwarding status is controlled by its

RRPP domain. Different RRPP domains on the same RRPP ring are configured with

different protected VLANs, and each RRPP domain controls the forwarding status of

ports in it independently.

2.1.5 Master NodeEach device on an RRPP ring is called an RRPP node. On an RRPP ring, you must


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configure only one as the master node. The master node initiates ring status

detection with the polling mechanism and makes operation decisions upon ring

topology changes. In Figure 1, S1 is the master node on the primary ring, and S6 is

the master node on the subring.

A master node can be in one of the following states:z Complete stateThe master node is in the complete state if it can receive at its secondary port the

Hello packets sent out its primary port. In this case, the master node blocks the

secondary port to prevent traffic loops.

z Failed stateWhen a link in the ring fails, the master node is in the failed state. To avoid traffic

interruption in the ring, the master node unblocks the secondary port to forward data

traffic.

Note:The state of the master node represents the state of the whole RRPP ring. That is,

when the master node is in the complete (failed) state, the RRPP ring is also in the

complete (failed) state.

2.1.6 Transit NodeAll the nodes except the master node on a ring are transit nodes. For example, in

Figure 1, S2, S3, and S4 are transit nodes on the primary ring, and S5 is a transit

node on the subring. A transit node transparently transmits Hello packets of the

master node, monitors the state of its directly connected RRPP links, and reports link

state changes (if any) to the master node to decide the actions to be taken.

A transit node can be in one of the following states depending on the states of its

primary and secondary ports:

z Link-up stateWhen both the primary port and secondary port are up, the transit node is in the link-

up state.


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z Link-down stateWhen either the primary port or the secondary port is down, the transit node is in the

link-down state.

z Pre-forwarding stateWhen either the primary port or the secondary port is blocked, the transit node is in

the pre-forwarding state.

2.1.7 Edge Node and Assistant-Edge NodeIn an RRPP domain, of the two nodes at which the primary ring and a subring

intersect, one is the edge node and the other is the assistant-edge node. You can

configure either of them as the edge or the assistant-edge but must ensure that the

roles of the two nodes are different. In Figure 1, S3 is the edge node, and S2 is the

assistant-edge node.

These two roles are significant only on subrings.

Edge nodes and assistant-edge nodes are special transit nodes. An edge or edge-

assistant node can be in one of the following three states depending on the state of

its edge port:z Link-up stateWhen the edge port is up, the node is in the link-up state.

z Link-down stateWhen the edge port is down, the node is in the link-down state.

z Pre-forwarding stateWhen the edge port is blocked, the node is in the pre-forwarding state.

The state transition of an edge or edge-assistant node is the same as that of a transit

node but it is triggered by the link state change of the edge port only.

2.1.8 Primary Port and Secondary PortOf the ports that connect a node to an RRPP ring, one is the primary port and the

other is the secondary port. You can configure them as needed.

The primary and secondary ports of master nodes are different in functions. A master

node sends HELLO messages out its primary port. If it can receive these HELLO


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messages on its secondary port, the master node considers the RRPP ring as

complete and thus blocks the secondary port to avoid loops. If the master node fails

to receive these HELLO messages within the specified period, it considers the ring as

having failed and unblocks the secondary port to ensure service continuity.

The primary and secondary ports of a transit node are the same in functions.

In an RRPP domain, the primary ring is a logical node of each subring and it transmits

subring RRPPDUs (except the EDGE-HELLO messages) transparently as data traffic.

Therefore, no data packet or subring RRPPDU (except the EDGE-HELLO messages)

can pass through a blocked port on the primary ring.2.1.9 Common Port and Edge Port

On an edge or assistant-edge node, the port connecting to the subring is called the

edge port while the two ports connecting to the primary ring are called common ports.

The link between the common port on the edge node and that on the assistant-edge

node is called the common link.

As a primary ring is considered as a logical node on its subrings, the common link is

considered as an internal link of the primary ring node. Thus, the common link state

changes are reported only to the master node of the primary ring.

In Figure 1, on the edge node S3, the port connecting to S6 is an edge port, while the

ports connecting to S4 and S2 are common ports. The link directly connecting the

edge node S3 to the assistant-edge node S2 is the common link.

2.2 RRPPDUs2.2.1 RRPPDU Types

RRPPDU type Description

HELLO

Sent regularly by a master node to check ringcompleteness. If the sent HELLO messages canfinally reach the secondary port of the master nodewithin the predefined period, the ring is consideredcomplete; if not, the ring is considered open, inwhich case a link may have failed on the ring.

LINK-DOWNSent by a transit, edge, or edge-assistant node toreport link failure to the master node.


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RRPPDU type Description

COMMON-FLUSH-FDB

Sent by a master node to notify the transit nodes toupdate their MAC address tables and ARP/ND

tables when it transitions to the failed state.The nodes on the primary ring must update theirMAC address table and ARP/ND tables afterreceiving COMMON-FLUSH-FDB messages, even ifthey are from the master node on a subring.

COMPLETE-FLUSH-FDB

Sent by a master node to notify the transit nodes toupdate their MAC address tables and ARP/NDtables when it transitions to the complete state. Thetransit nodes thus transition to the link-up state,unblocking the temporarily blocked ports.

For the nodes on the primary ring, if the sending

master node is on a subring, they will update theMAC address tables and ARP/ND tables, but will notunblock the blocked ports.

EDGE-HELLO

Sent by the edge node of a subring and received bythe assistant-edge node of the same subring tocheck whether the SRPTs of the subring are in goodcondition.

The edge node periodically sends EDGE-HELLOmessages out the two common ports to theassistant-edge node across the primary ring. If theassistant-edge node receives the messages, theSRPTs are considered as in good condition; if theassistant-edge node does not receive the messageswithin a specified period of time, the SRPTs areconsidered as faulty.

MAJOR-FAULTSent by an assistant-edge node to report SRPTfailure to the edge node. Upon receiving a MAJOR-FAULT message, the edge node blocks its edgeport.


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2.2.2 RRPPDU Format 0 7

Destination MAC Address (6 bytes)

15 23 31 39 47

Source MAC Address (6 bytes)

EtherType PRI VLAN ID Frame Length

DSAP/SSAP

0x00bb

CONTROL OUI = 0x00e02b

0x99 0x0b RRPP Length

RRPP_VER RRPP Type Ring IDDomain ID

0x0000 SYSTEM_MAC_ADDR (6 bytes)

HELLO_TIMER FAIL_TIMER

0x00000x00000x00 LEVEL

RESERVED(0x000000000000)

RESERVED(0x000000000000)

RESERVED(0x000000000000)

RESERVED(0x000000000000)

RESERVED(0x000000000000)

RESERVED(0x000000000000)

Figure 2 RRPP RRPPDU format

The following table describes each field in an RRPPDU: Field Length (in bits) Description

Destination MACAddress

48Destination MAC address, in therange of 0x000FE2078217 to0x000FE2078416.

Source Mac Address 48Source MAC address, fixed to0x000fe203fd75.

EtherType 8Encapsulation type, fixed to0x8100 indicating taggedencapsulation.

PRI 4Class of service (CoS) priority,fixed to 0xe0.

VLAN ID 12ID of the VLAN to which thepacket belongs.

Frame Length 16Ethernet frame length, fixed to0x48.

DSAP/SSAP 16Destination service accesspoint/source service accesspoint, fixed to 0xaaaa.

CONTROL 8 Fixed to 0x03.


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Field Length (in bits) Description

OUI 24 Fixed to 0x00e02b.

RRPP Length 16RRPP protocol data unit length,fixed to 0x40.

RRPP_VER 16 RRPP version, 0x0001 currently.

RRPP Type 8

RRPPDU type:

z 5: HELLOz 6: COMPLETE-FLUSH-FDBz 7: COMMON-FLUSH-FDBz 8: LINK-DOWNz 10: EDGE-HELLOz 11: MAJOR-FAULT

Domain ID 16ID of the RRPP ring to which thepacket belongs.

Ring ID 16ID of the RRPP ring to which thepacket belongs.

SYSTEM_MAC_ADDR 48Bridge MAC address of the nodesending the packet.

HELLO_TIMER 16Hello timer setting (in seconds)of the sending node.

FAIL_TIMER 16Fail timer setting (in seconds) ofthe sending node.

LEVEL 8Level of the RRPP ring to whichthe packet belongs.

2.3 Single Ring Fundamentals2.3.1 Single-Domain Single Ring

This section describes how RRPP works and how ring topology converges by

analyzing the Ethernet ring status change from complete to failed, and then back to

complete.

1. Ring status detection and related operations

RRPP uses a polling mechanism to check ring completeness: the master node sends

Hello messages to the ring regularly. These Hello messages pass through each


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transit node on the ring in turn. If they can finally reach the secondary port of the

master node, the ring is considered complete. In this case, to avoid broadcast loops

on the ring, the master node keeps its secondary port blocked. Figure 3 shows a

closed RRPP ring.

Data Packet

Control PacketS

P

MasterHELLO

B

P - Primary Port

- Secondary Port

- Blocked Port

SB

Single Ring Complete state

Complete state

S port blocked

Figure 3A complete RRPP ring

2. Fault detection and related operations

Ring faults can be detected by using one of the following mechanisms:

z Polling mechanism

z Link down alarm mechanism

1) Polling mechanism

RRPP uses a polling mechanism to check ring faults.

With this mechanism, a master node sends Hello messages to the ring regularly.

These Hello messages pass through each transit node on the ring in turn. If they fail

to reach the secondary port of the master node within a specified period of time, the

ring is considered open, in which case at least one link may have failed on the ring. In

this case, the master node transitions to the failed state, unblocks the secondary port,

and sends COMPLETE-FLUSH-FDB messages out its primary and secondary ports

to instruct all the transit nodes to update their MAC address table entries and


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ARP/ND entries.

2) Link down alarm mechanism

A node is always monitoring its own port link status, and takes immediate actionsupon detecting a failed port.

z When a master nodes primary port goes down, the master node is able to

sense the link fault by itself. It immediately unblocks its secondary port, and

sends a COMPLETE-FLUSH-FDB message out its secondary port to instruct all

the transit nodes to update their MAC address table entries and ARP/ND entries.

z When one port on a transit node goes down, the transit node sends a LINK-

DOWN message out the other RRPP port that is still up to notify the master

node, as shown in Figure 4. Upon receiving the message, the master node

unblocks its secondary port and transitions to the failed state. To avoid packet

direction errors due to the topology change, the master node updates its own

MAC address table and ARP/ND entries and sends a COMMON-FLUSH-FDB

message out its primary and secondary ports to instruct all the transit nodes to

update their MAC address table entries and ARP/ND entries. See Figure 5 for

the process of a master node transitioning from the complete state to the failed

state.

Data Packet

Control PacketS

P

Master

LINK-DOWN

B

P - Primary Port

- Secondary Port

- Blocked Port

SB

Transit Send LINK-DOWN to MasterLink failure

Figure 4A transit node sends a LINK-DOWN message to the master node


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Data Packet

Control PacketS

P

Master

B

P - Primary Port

- Secondary Port

- Blocked Port

S

Master Transfer to Failed State

Transfer to Failed State

Unblock S port

COMMON-FLUSH-FDB

Figure 5 The master node transitions to the failed state

The link-down alarm mechanism provides faster fault protection than the polling

mechanism. However, if LINK-DOWN messages are lost on the way to the master

node, the link faults will be detected later by the master node using the polling

mechanism. If the master node fails to receive on its secondary port the Hello

messages it sends out within a period of time specified by the Fail timer, it considers

the ring topology as faulty, and then takes related actions as described earlier.

3. Fault recovery detection and related operations

When a failed port on a transit node recovers, the master node cannot be notified of

the recovery immediately. Hence, the master ports secondary port is still up. If the

transit node transitions to the Link-Up state at once, a temporary loop will be created

on the ring. Therefore, when a Link-Down transit nodes primary and secondary ports

are both recovered, the transit node blocks them immediately and transitions to the

pre-forwarding state, as shown in Figure 6. At this point, the ring is not recovered yet.

The master node initiates the ring recovery process.


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Data Packet

Control PacketS

P

Master

B

P - Primary Port

- Secondary Port

- Blocked Port

S

Transit block restored port temporarily

at Failed State

BB

Transfer to preforwarding

state & block restored port

Figure 6A transit node blocks its recovered ports and transitions to the pre-forwarding state

When all the links on the ring recover and the master node is able to receive its own

Hello packets again, it blocks the secondary port and transitions back to the complete

state. Because of the ring topology change, the master node needs to update its

MAC address table entries and ARP/ND entries, and sends COMPLETE-FLUSH-FDB

messages to instruct all the transit nodes to update their MAC address table entries

and ARP/ND entries. When receiving the COMPLETE-FLUSH-FDB message from

the master node, the transit nodes in the pre-forwarding state transition to the Link-Up

state. Thus the ring is recovered, as shown in Figure 7.


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Data Packet

Control PacketS

P

MasterCOMPLETE-FLUSH-FDB

B

P - Primary Port

- Secondary Port

- Blocked Port

SB

Master transfer to Complete state

Transfer to Link-Up State

& Unblock port

Transfer to Complete state

& block S port

Figure 7 How a ring recovers

In case the COMPLETE-FLUSH-FDB messages fail to reach a transit node, the

transit node in the pre-forwarding state unblocks the blocked port automatically,

updates its MAC address table entries and ARP/ND entries and transits to the link-up

state if it fails to receive any COMPLETE-FLUSH-FDB messages from the master

node within the period of time specified by the Fail timer.

2.3.2 Multi-Domain Single Ring

If traffic of multiple VLANs exists on an RRPP ring, you can configure multiple RRPP

domains on the RRPP ring, with each domain transmitting traffic for different VLANs

(protected VLANs). In this way, data traffic of different VLANs is transmitted along

different paths on the ring, thus achieving load sharing.


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Figure 8 Multi-domain single ring

As shown in Figure 8, Ring 1 is configured as the primary ring in both Domain 1 and

Domain 2. Domain 1 and Domain 2 have different protected VLANs. In Domain 1,

Device A is configured as the primary node on Ring 1, while in Domain 2, Device B is

configured as the primary node on Ring 1. Under such configurations, traffic of

different VLANs is transmitted along different paths.

2.4 Intersecting Ring Fundamentals

2.4.1 Single-Domain Intersecting Rings

In a single-domain intersecting rings topology, the implementation of the primary ring

and the fault detection mechanism used by the subrings master nodes are the same

as those used on a single-ring topology. The difference is that the SRPT state

detection mechanism is used on a multi-ring topology to prevent data loops on the

subrings when both SRPTs are disconnected. Before the master node on a subring

unblocks its secondary port, the edge node blocks its edge port, thus preventing

broadcast loops on the subrings. For more information about the SRPT state

detection mechanism, refer to SRPT State Detection Mechanism.Additionally, when the nodes on the primary ring receive COMMON-FLUSH-FDB or

COMPLETE-FLUSH-FDB messages from a subring, they must update their MAC

address table entries and ARP/ND entries. However, the COMPLETE-FLUSH-FDB

messages from a subring cannot make a transit node on the primary ring to unblock

its temporarily-blocked port.


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Device A Device B

Device CDevice D

Device E

Edge node

Master node

Transit node

Assistant edge node

Domain 1

Ring 1 Ring 2

Master node

Figure 9 Single-domain intersecting rings

2.4.2 Multi-Domain Intersecting Rings If traffic of multiple VLANs exists in an intersecting RRPP rings topology, you can

configure multiple RRPP domains for the intersecting rings, with each domain

transmitting traffic for the specified protected VLANs. Each RRPP domain in the multi-

domain topology works in the same way as a single domain does. In this way, data

traffic of different VLANs is transmitted along different paths on the ring, thus

achieving load sharing.

Device A Device B

Device CDevice D

Device E

Ring 1 Ring 2Domain 1 Domain 2

Figure 10 Multi-domain intersecting rings

As shown in Figure 10, Ring 1 and Ring 2 are respectively configured as the master

ring and subring in both Domain 1 and Domain 2. They have different protected


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VLANs. In Domain 1, Device A is configured as the master node of Ring 1, while in

Domain 2, Device D is configured as the master node of Ring 1. In both Domain 1

and Domain 2, Device E is configured as the master node of Ring 2. However, for

Domain 1 and Domain 2, the primary and secondary ports on Device E are different.

In this way, traffic of different VLANs can be transmitted along different paths in the

primary ring and subrings, thus achieving load sharing on the intersecting rings.

2.4.3 SRPT State Detection Mechanism1. Introduction to SRPT state detection mechanism

SRPTs are tunnels for subring packets on the primary ring. The primary ring as a

whole serves as a logical node on the subrings, and protocol packets from the

subrings are transparently transmitted through the primary ring. The primary ring

forwards protocol packets (except EDGE-HELLO packets) from the subrings as data

packets.

Each subring has two SRPTs. As shown in Figure 11, the two SRPTs for subrings

Ring 2 and Ring 3 are S3-S2 and S3-S4-S1-S2. When the primary ring is healthy, the

secondary port of its master node is blocked, in which case only the S3-S2 tunnel is

available. When fault occurs on the S3-S4-S1-S2 tunnel, the S3-S2 tunnel is

available; when fault occurs on the S3-S2 tunnel, the S3-S4-S1-S2 tunnel is available.

In other words, of a subrings two SRPTs, only one of them is available at any point of

time, thus preventing data loops on the primary ring for subring protocol packets.

When both the SRPTs of a subring fail, and the subrings master node fails to receive

its own Hello packets within the period of time specified by the Fail timer, the

subrings master node unblocks its secondary port. In this way, the subring can

restore communication to the maximum extent without creating data loops.

This works fine in a common RRPP network topology but not in a dual-homed RRPP

ring topology. As shown in Figure 11, the two subrings Ring 2 and Ring 3 are

interconnected through the edge node and assistant-edge node and form a loop

naturally. Therefore, data loops are unavoidable when the secondary ports on the

master nodes of the subrings are unblocked after the two SRPTs on Ring 1 went

down. The arrows in the figure indicate traffic directions.


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Figure 11 Loops in a dual-homed ring topology without SRPT state detection

To address the problem, the SRPT state detection mechanism is introduced, which is

carried out by the edge and assistant-edge nodes together. When the edge node

detects that both the SRPTs are down, it blocks the edge ports on the edge nodes

before the secondary ports on the master nodes of the subrings are both unblocked.

Thus, loops are avoided. Figure 12 shows how loops are removed with the SRPT

state detection mechanism.

Figure 12 Loop removal in a dual-homed ring topology with SRPT state detection


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2. SRPT state detection process

In the SRPT state detection mechanism, the edge node initiates SRPT state

detection and determines the actions to take; the assistant-edge node monitors SRPT

state and notifies the edge node of SRPT state changes, if any. The following

subsections describe how the mechanism works.1) Detecting SRPT stateThe edge node of a subring periodically sends EDGE-HELLO messages destined for

the assistant-edge node out the two ports connecting the subring to the SRPTs. The

EDGE-HELLO messages travel through each node on the SRPTs, as shown in

Figure 13. If at least one SRPT is normal for transmitting subring protocol packets,

the assistant-edge node can receive these EDGE-HELLO messages within the

specified period of time. If the two SRPTs are both disconnected and the subring

protocol packets cannot travel through the primary ring, the assistant-edge node

cannot receive these EDGE-HELLO messages within the specified period of time.

Data Packet

Control PacketS

P

PS

Master

Edge

Assistant

Master

Major ring Sub ring

EDGE-HELLO

B

B

B

P - Primary Port- Secondary Port

- Blocked Port

S

Figure 13 The edge node sends EDGE-HELLO messages

2) Blocking the edge port of the edge node when the SRPTs are disconnectedUpon detecting that the two SRPTs are both disconnected, the assistant-edge node

sends MAJOR-FAULT messages out the edge port to the edge node through the

subring. If the subring is normal, the edge node can receive these MAJOR-FAULT


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messages. Upon receiving the MAJOR-FAULT messages, the edge node blocks its

edge port as shown in Figure 14. If the subring fails, the edge port of the edge node

will not be blocked.

MAJOR-FAULT messages are sent periodically. If the edge node receives them, its

edge port stays blocked; if the edge node fails to receive any MAJOR-FAULT

message within the specified period of time, its edge port is unblocked automatically.

Data Packet

Control PacketS

P

PS

Master

Edge

Assistant

Master

Major ring Sub ring

MAJOR-FAULT

B

B

P - Primary Port

- Secondary Port- Blocked Port

S

B

Figure 14 The edge node blocks its edge port upon receiving MAJOR-FAULT messages

3) Transitioning to the failed state when the subring failsAs the master node on the subring cannot receive the HELLO messages it sent out

due to disconnection of the two SRPTs, it unblocks its secondary port and transitions

to the failed state, as shown in Figure 15.


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Data Packet

Control PacketS

P

P

S

Master

Edge

Assistant

Master

Major ring Sub ring

B

P - Primary Port

- Secondary Port

- Blocked Port

S

B

Figure 15 The subrings master node transitions to the failed state due to SRPT disconnection

4) SRPT recoveryWhen the primary ring recovers, the SRPTs also recover. Therefore, the assistant-

edge node stops sending MAJOR-FAULT messages.

In this case, if the subring is normal, its master node can receive its own Hello

packets again, and thus blocks its secondary port and transitions to the complete

state, as shown in Figure 16.


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Data Packet

Control PacketS

P

PS

Master

Edge

Assistant

Master

Major ring Sub ring

HELLO

B

B

P - Primary Port

- Secondary Port

- Blocked Port

S

B

Figure 16 SRPT recovery

After the subring is recovered, its master node sends COMPLETE-FLUSH-FDB

messages out the primary port. Upon receiving the COMPLETE-FLUSH-FDB

messages, the edge node unblocks its edge port if the port is blocked, as shown in

Figure 17. Thus, communication in the entire network is recovered.

Data Packet

Control PacketS

P

PS

Master

Edge

Assistant

Master

Major ring Sub ring

COMPLETE-FLUSH-FDB

B

B

P - Primary Port

- Secondary Port

- Blocked Port

S

Figure 17 The edge node of the subring unblocks the edge port


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If a fault is present on the subring when the SRPTs recover, the subring cannot be

recovered. In this case, the master node of the subring does not send COMPLETE-

FLUSH-FDB messages and the blocked edge port of the edge node will be

unblocked only after the Fail timer expires.

3. Ring group

In SRPT state detection, the edge node and assistant-edge node of subrings

respectively sends and receives EDGE-HELLO packets frequently. As shown in 1.

Figure 11 in the multi-ring dual-homed topology, if you configure S2 and S3 as the

edge node and assistant-edge node of both Ring 2 and Ring 3, S2 needs to send

EDGE-HELLO packets for both Ring 2 and Ring 3, while S3 needs to receive EDGE-

HELLO packets for both Ring 2 and Ring 3. The more subrings are configured, the

more EDGE-HELLO packets will occur in the network, thus increasing the CPU load

of the devices.

To reduce Edge-Hello traffic, you can configure a group of subrings on the edge node

or assistant-edge node. A ring group configured on the edge node is called an edge

node ring group, and a ring group configured on an assistant-edge node is called an

assistant-edge node ring group. In an edge node ring group, only an active subringwith the smallest domain ID and ring ID sends EDGE-HELLO packets; in an

assistant-edge node ring group, a random active subring receives the EDGE-HELLO

packets and passes the information to other active subrings. In this way, after subring

groups are configured on the edge node and assistant-edge node, only one subring

in each group sends/receives EDGE-HELLO packets, thus reducing the device CPU

load significantly.

You must configure a device as the edge node of these subrings, and another device

as the assistant-edge node of these subrings. Additionally, these subrings must have

the same SRPTs.


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3 Application Scenarios 3.1 Single-Domain Single Ring

Device A Device B

Device CDevice D

Master node

Transit node

Domain 1

Ring 1

Transit node

Transit node

Figure 18 Network diagram for a single-domain single-ring network

A single-domain single-ring network has only one ring. Therefore, you need to define

only one RRPP domain and one RRPP ring.

A single-domain single-ring network features fast response to topology changes and

fast topology convergence.

3.2 Multi-Domain Single Ring

Figure 19 Network diagram for a multi-domain single-ring network


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A multi-domain single-ring network has only one ring, but multiple VLANs for the

purpose of load sharing. Multiple RRPP domains are configured in the network, each

having its own protected VLANs. In addition, an RRPP ring has different master

nodes in different RRPP domains or has the same master node but different

primary/secondary ports in different RRPP domains. Therefore, the protected VLANs

of different RRPP domains have different logical topologies.

3.3 Tangent Rings

Ring 1

Device A

Device B

Device C

Device E

Master node

Domain 1

Transit node

Device D

Transit node

Transit node

Ring 2

Device F

Master node

Transit node

Domain 2

Figure 20 Network diagram for a tangent-ring network

A tangent-ring network contains two or more rings. Every two rings have only one

common node. For each ring, you are required to define an independent RRPP

domain.The tangent-ring topology is suitable for large-scale networks that require networks at

the same level to be managed as independent domains.


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3.4 Single-Domain Intersecting RRPP Rings

Device A Device B

Device CDevice D

Device E

Edge node

Master node

Transit node

Assistant edge node

Domain 1

Ring 1 Ring 2

Master node

Figure 21 Networking diagram for single-domain intersecting rings

A single-domain intersecting-ring network contains two or more rings. Every two rings

have two common nodes. In this case, you can define one RRPP domain. In the

domain, configure a ring as the primary ring and the other rings as subrings.

A typical single-domain intersecting-ring topology is dual-homed rings where the

master node of a subring is dually uplinked to the primary ring through the edge node

and the assistant-edge node for uplink backup.

3.5 Multi-Domain Intersecting RRPP Rings

Device A Device B

Device CDevice D

Device E

Ring 1 Ring 2Domain 1 Domain 2

Figure 22 Networking diagram for multi-domain intersecting rings


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H h H3C T h l i C Ltd 30/30

A multi-domain intersecting-ring network contains two or more rings. Every two rings

have two common nodes. To achieve load sharing when data traffic of multiple

VLANs exists in the network, you can configure multiple RRPP domains in the

network, each having its own protected VLANs. In addition, an RRPP ring has

different master nodes in different RRPP domains or has the same master node but

different primary/secondary ports in different RRPP domains. In this way, the

protected VLANs of different RRPP domains can have different logical topologies.

3.6 RRPP in Combination with STPRRPP is mutually exclusive with STP on a port because RRPP may conflict with STP

in port state calculation. An RRPP ring can be connected to an STP ring only in the

tangent mode, where no common ports exist between rings.

Figure 23 RRPP in combination with STP

Copyright 2008 Hangzhou H3C Technologies Co., Ltd. All Rights ReservedExtracting and copying partial or whole contents of the document without H3Cs written permission is prohibited.

The information is this document is subject to due modification.

Date post:	14-Apr-2018
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