OpenFlow协议1.2版本详解：支持IPv6

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"OpenFlow协议1.2是Software Defined Networking (SDN)领域的一个关键标准，由Open Networking Foundation (ONF)发布。该版本在2011年12月推出，是对之前版本（如1.1和1.0）的升级和发展。OpenFlow协议的核心目标是使网络设备的转发平面能根据来自OpenFlow控制器的指令处理数据包，实现对网络流量的精细控制。" 在OpenFlow 1.2中，主要包含了交换机规范的更新，这个规范定义了OpenFlow交换机如何接收、响应来自OpenFlow控制器的消息，并基于这些消息调整其转发策略。这种对话机制旨在指导交换机的转发平面以特定方式处理入站数据包。 OpenFlow 1.2的显著改进包括： 1. **IPv6支持**：除了原有的对IPv4、MPLS和二层头部的支持，OpenFlow 1.2增加了对IPv6源地址、目的地址和协议字段的匹配能力。这使得网络管理者能够更灵活地针对IPv6流量进行策略设定和管理。 2. **扩展的流表项**：版本1.2扩展了流表项的匹配字段，允许更精确的流量匹配条件，从而增强了网络控制的粒度。例如，可以依据更丰富的TCP/UDP端口、ICMP类型和代码等字段来定义流规则。 3. **多供应商互操作性**：为了提高不同厂商设备间的互操作性，OpenFlow 1.2引入了更多的标准化接口和协议，这有助于确保不同供应商的OpenFlow设备能够在同一网络环境中无缝协作。 4. **增强的安全特性**：新版本加强了安全机制，例如增加了对安全通道的强化，以保护控制器与交换机之间的通信不受攻击。 5. **流表大小和流条目数量**：OpenFlow 1.2可能支持更大的流表和更多的流条目，以适应更大规模的网络环境和更复杂的流量控制需求。 6. **批量操作支持**：协议增加了对批量操作的支持，允许控制器一次性发送多个命令，提高了网络配置和更新的效率。 7. **更好的性能和效率**：通过优化协议的传输和处理机制，OpenFlow 1.2提升了整体性能，降低了延迟，并提高了资源利用效率。 OpenFlow 1.2的发布标志着SDN技术的进步，它为网络管理员提供了更强大的工具来实现动态、自适应和灵活的网络管理，同时也为未来的其他组件（如OF-Config和OF-Test）奠定了基础，这些组件将进一步完善SDN的生态系统。随着OpenFlow协议的不断演进，SDN技术在数据中心、广域网和未来网络架构中的应用将更加广泛和深入。

OpenFlow Switch Speciﬁcation Version 1.2

support all counters, just those marked “Required” in Table 3.

Duration refers to the amount of t im e the ﬂ ow has been installed in the switch, and must be tracked with

second pr e ci si on . The Receive Errors ﬁeld is the total of all receive and coll is i on errors deﬁned in Table 3,

as well as any others not called out in t h e table.

Counters are unsign ed and wrap around with no overﬂow i nd i cat or . If a speciﬁc numeric counter is

not available in the s wi t ch, its value should be set to the maximum ﬁeld value (the unsigned equivalent of

-1).

Counter Bits

Per T able

Reference count (active entries) 32 Required

Packet Lookups 64 Optional

Packet Matches 64 Optional

Per Flow

Received Packets 64 Optional

Received Bytes 64 Optional

Duration (seconds) 32 Required

Duration (nanoseconds) 32 Optional

Per Port

Received Packets 64 Required

Transmitted Packets 64 Required

Received Bytes 64 Optional

Transmitted Bytes 64 Optional

Receive Drops 64 Optional

Transmit Drops 64 Optional

Receive Errors 64 Optional

Transmit Errors 64 Optional

Receive Frame Alignment Erro rs 64 Op tio na l

Receive Overrun Errors 64 Optional

Receive CRC Errors 64 Optional

Collisions 64 Optional

Per Queue

Transmit Packets 64 Required

Transmit Bytes 64 Optional

Transmit Overrun Errors 64 Optional

Per Group

Reference Count (ﬂow entries) 32 Optional

Packet Count 64 Optional

Byte Count 64 Optional

Per Bucket

Packet Count 64 Optional

Byte Count 64 Optional

Table 3: List of counters

5.6 Instructions

Each ﬂow entry contains a set of instruc t i ons that are executed when a packet matches the entry. These

instructions result in changes to the packet, action set and/or pipeline processing.

A switch is not required to support all action types , just those marked “Required Instruction” below. The

OpenFlow Switch Speciﬁcation Version 1.2

controller can also query the switch about which of the “Optional Instr u ctio n” it supports.

• Optional Instruction: Apply-Actions action(s): Applie s the speciﬁc action(s) immediately, without

any change to the Action Set. This inst r u ct i on may be used to modify the packet between two tables

or to execute multiple actions of the same type. The actions are speciﬁed as an action list ( se e 5.8).

• Optional Instruction: Clear-A ction s : Clears all the actions in the action se t immediately.

• Required Instruct ion : Write-Actions action(s): Merges th e speciﬁed act i on( s ) into the current

action set (see 5.7). If an ac t ion of the gi ven type exists in the curre nt set, overwrite it, otherwise add

it.

• Optional Instruction: Write-Metadata metadata / mask : Writes the masked metadata value into

the met ad at a ﬁeld. The mask speciﬁes which bits of the metadata register should be modiﬁed (i.e.

new metadata = old metadata & ˜mask | value & mask).

• Required Instruction: Goto-Table next-table-id : Indicates the next table in the processing pipeline.

The tabl e -i d must be greater than the current table-id. The ﬂows of last table of the pipeline can not

include this instruction (see 5.1).

The inst ru ct i on set associated with a ﬂow entry contains a maximum of one instruction of each type.

The instructions of the set execute in the order speciﬁed by this above list . In practice, the onl y constraints

are that the Clear-Actions instruction is execut ed before the Write-Actions instruction, and that Goto-Table

is ex ec ut e d last.

A switch may reject a ﬂow entry if it is unable to execute the instructions associated with the ﬂow

entry. In this case, the switch must r et u rn an unsupported ﬂow error (see 6.7). Flow tables may not support

every match, every instruction and every actions.

5.7 Action Set

An action set is associated with each packet. This set is empty by default. A ﬂow entry can modify the

action set using a Write-Action instruction or a Clear-Action i n st r uc t ion associated with a particular match.

The action set is carried between ﬂow tables. When the in st r uc ti on set of a ﬂow entry does not contain a

Goto-Table instruct i on , pipeline processing stops and the actions in the action set of t h e packet are executed.

An acti on set contains a maximum of one action of each type. The set-ﬁeld actions are identiﬁed

by their ﬁeld types, therefore the action set contains a maximum of one set-ﬁeld action for each ﬁeld

type (i.e. multiple ﬁelds can be set). Whe n multiple actions of the same type are required, e.g. pushing

multiple MPLS labels or popping multiple MPLS labe l s, the Apply-Actions instructi on may be used (see 5.8).

The action s in an action set are applied in the order speciﬁed below, regardless of the order that

they were added to the set. If an action set contains a group action, the actions in the appropriate action

bucket of the group are also applied i n the order speciﬁed below. The switch may support arbitrary action

execution order through the action list of the Apply-Actions instruction.

1. copy TTL inwards: apply copy TTL inward actions to the packet

2. pop: apply all tag pop actions to the packet

3. push: apply all tag push actions to the packet

4. copy TTL outwards: apply copy TTL outwards action to the packet

5. decrement TTL: apply decrement TTL action to the packet

OpenFlow Switch Speciﬁcation Version 1.2

6. set: apply all set-ﬁeld actions to the p acket

7. qos: apply all QoS actions, such as set queue to the packet

8. group: if a group ac ti on is speciﬁed, apply the actions of the relevant group bucket(s) in the order

speciﬁed by this list

9. output: if no group action is speciﬁed, forward the packet on the port speciﬁed by the output action

The output action in the action set is executed last. If both an out pu t action and a group action are

speciﬁed in an action set, the output action is ignored and the group acti on takes precedence. If n o output

action and n o group action were speciﬁed in an action set, the packet is dropped. The execution of groups

is recursive if the switch supports it ; a group bucket may spe ci fy anot h er group , in which case the execution

of act ion s traverses all the groups speciﬁed by the group conﬁguration.

5.8 Action List

The Apply-Acti ons instruction and the Packet-out message include an action list. The semantic of the

action list is identical to the OpenFlow 1.0 speciﬁcation. The actions of an action list are executed in the

order sp ec iﬁ ed by the list, and are applied immediately to the packet.

The execution of an action list start with the ﬁrst action in the list and each action is executed on

the packet in sequence. The eﬀect of those actions is cumulative, if the action list contains two Push VLAN

actions, two VLAN headers are added to the packet. If the action list c ontains an output act ion , a c opy of

the packet is forwarded in its current state to the desired port. If the list contains a group actions, a copy

of th e packet in its current state is processed by the relevant group buckets.

After the execution of the action l i st in an Apply-Actions instructi on , pipeline execution continues

on the modi ﬁ ed packet (see 5.1). The action set of the packet is unchanged by the execution of the action

list.

5.9 Actions

A switch is not required to support all action types, just those marked “Requi red Action” below. The

controller can also query the switch about which of the “Optional Action” it supports.

Required Action: Output. The Output action forwards a packet to a speciﬁe d OpenFlow port (see

4.1). OpenFlow switches must support forwarding to physical ports, switch-deﬁned logical ports and the

required reserved ports (see 4.5).

Optional Action: Set-Queue. The set-queue action set s the queue id for a packet. When the

packet is forwarded to a port using the output action, the queue id determines which queue attached to this

port is used for forwarding the packet. Forwarding behavior is dictated by the conﬁguration of the queue

and i s used to provide basic Quality-of-Service (QoS) support (see section A.2.2).

Required Action: Drop. There is no explicit action to represent drops. Instead, packets whose ac-

tion sets have no output actions should be dropped. This result c oul d come from empty instruct i on sets or

empty action buckets in the pr ocessing pipeline, or after executing a Clear-Actions instruction.

Required Action: Group. Process the packet through the speciﬁed group. The e x act interpret at i on

depends on group type.

Optional Action: Push-Tag/Pop-Tag. Switches may support the ability to push/pop tags as shown in

OpenFlow Switch Speciﬁcation Version 1.2

Table 4. To aid integration with exi st i n g networks, we suggest that the abil ity to push/pop VLAN tags be

supported.

The or de ri n g of header ﬁelds/tags is:

Ethernet VLAN MPLS ARP/IP TCP/UDP/SCTP (IP-only)

Newly pushed tags should always be inserted as the outermost tag in this ordering. When a new VLAN tag

is pushed, it should be the outermost VLAN tag inserted immediately after the Ethernet header. Likewise,

when a new M PLS tag is pushed, i t should be the outermost MPLS tag, inserted as a shim header after any

VLAN tags.

Note: Refer to section 5.9.1 for information on default ﬁeld values.

Action Associated Data Description

Push VLAN header Ethertype Push a new VLAN header onto the packet.

The Ethertype is used as the Ethertype for the tag. Only

Ethertype 0x8100 and 0x88a8 should be used .

Pop VLAN header - Pop the outer-mo st V LA N head er from the pa cket.

Push MPLS header Ethertype Push a new MPLS shim header onto the packet.

The Ethertype is used as the Ethertype for the tag. Only

Ethertype 0x8847 and 0x8848 should be used .

Pop MPLS header Ethertype Pop the outer-most MPLS tag or shim header from the

packet.

The Ethertype is used a s the Ethertype for the resulting

packet (Ethertype for the MPLS payload).

Table 4: Push/pop tag actions.

Optional Action: Set-Field. The various Set-Field actions are identiﬁed by their ﬁeld type an d modify the

values of respective heade r ﬁelds in the packet. While not strictly req ui r ed , the support of rewriting various

header ﬁelds using Set-Field actions greatly increase the usefulness of an OpenFlow imple mentation. To

aid integration with exist i ng networks, we suggest that VLAN modiﬁcation act i ons be supported. Set -F i el d

actions should always be applied to the outermost-possible header (e.g. a “Set VLAN ID” acti on always

sets the ID of the outermost VLAN tag), unless the ﬁeld type speciﬁes otherwise.

Optional Action: Change-TTL. The various Change-TTL actions modify the values of the IPv4

TTL, IPv6 Hop Limit or MPLS TTL in th e packet. While not strictly required, the actions shown in

Table 5 greatly increase the usefulness of an OpenFlow imp le mentation for i mp le m e nting routing fu nc t ion s.

Change-TTL actions shou l d always be applied to the outermost-possible header.

Action Associated Data Description

Set MPLS TTL 8bits:NewMPLSTTL Repla c e the existing MPLS TTL. Only applies to packets

with an existing MPLS shim header.

Decrement MPLS TTL - Decrement the MPLS TTL. Only ap p l ie s to packets with

an existing MPLS shim header.

Set IP TTL 8bits:NewIPTTL Replace the existing IPv4 TTL or IPv6 Hop Limit and up-

date the IP checksum. Only applies to IPv4 and IPv6 pack-

ets.

Table 5 – Continued on next page

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