WO2014059864A1

WO2014059864A1 - Network switching apparatus

Info

Publication number: WO2014059864A1
Application number: PCT/CN2013/084287
Authority: WO
Inventors: Yujie LIANG; Wei Wang
Original assignee: Hangzhou H3C Technologies Co., Ltd.
Priority date: 2012-10-18
Filing date: 2013-09-26
Publication date: 2014-04-24
Also published as: CN103780503B; CN103780503A

Abstract

A network switching apparatus comprising a processor, a first network interface comprising a first network port for exchanging data with a first network, a second network interface comprising a plurality of second network ports for exchanging data with a second network, and a processor to process multicast traffic between the first network and the second network, wherein the network switching apparatus is to distribute multicast traffic designated to multicast groups among said plurality of second network ports.

Description

NETWORK SWITCHING APPARATUS

BACKGROUND

[001 ] Many communication applications require data to be delivered from a sender to many receivers. Examples of such applications include on-line lectures such as webinars, on-line or web conferencing, software updates, newsletter sending and real-time news delivery. A process where data is delivered from a sender to many receivers in a network is commonly called 'multicast', applications that involve a multicast data delivery are called 'multicast applications', and the receivers which are to receive data from the sender are collectively referred to as a 'multicast group'. [002] The size of a multicast group is not limited and a multicast group can include a very large number of receivers. In general, members of a multicast group can be geographically dispersed, and members of a multicast group can join or leave a multicast group at any time.

[003] As multicast operations can involve high volume data transmissions to a large number of members at the same time, efficient data delivery is between source and a large number of destinations is highly desirable.

DESCRIPTION OF FIGURES

[004] The disclosure will be described by way of non-limiting example with reference to the accompanying Figures, in which:- Figure 1 is a schematic diagram depicting an example network comprising a network switching apparatus and routers,

Figure 2 is a functional block diagram depicting an example network switching apparatus according to the disclosure,

Figure 3 is a flow diagram depicting example operation of the example network switching apparatus of Figure 2 to distribute multicast traffic among a plurality of forwarding devices, _n

2

Figure 4 is a flow diagram depicting example distribution of multicast traffic among a plurality of forwarding devices,

Figure 5 is a flow chart depicting an example multicast traffic distribution process, Figure 6 is a flow chart depicting an example process to switch from the example process of Figure 5 to one with no traffic distribution, and

Figure 7 is a flow diagram depicting example operation of example network switching apparatus according to this disclosure.

DESC IPTION OF EXAMPLES [005] In general, there is disclosed a method of forwarding multicast traffic to a network which is accessible through a plurality of forwarding apparatus, the method comprising allocating the multicast traffic among said plurality of forwarding apparatus according to a predetermined allocation scheme. In operation, when multicast traffic M is forwarded to the network switching apparatus 100 as depicted in Figure 1 , the multicast traffic M will be divided into multicast traffic groups ml , m2, m3 and forwarded as multicast traffic ml to Router A, as multicast traffic m2 to Router B, and as multicast traffic m3 to Router C.

[006] As depicted in Figure 3, upon receipt of multicast traffic at step 310, traffic distribution will be performed at step 320 according to multicast groups, and the multicast traffic will be forwarded to designated forwarding apparatus at step 330. More specifically, and as depicted in Figure 4, upon receipt of multicast traffic at step 350, the multicast traffic will be distributed among a plurality of forwarding apparatus at 360, and the inbound multicast traffic will be forwarded to the allocated forwarding apparatus for forwarding to destinations at step 370. [007] For example, the allocation scheme may be by sequential allocation, by distribution according to load requirements of the multicast groups, or by hashing with reference to group addresses. When traffic is based on the Internet Group Management Protocol (IGMP), a multicast router will be present to generate inquiries known as IGMP queries. This multicast router is known as Querier in IGMP. Allocating multicast traffic among a plurality of forwarding apparatus such as switches or routers would bring about more efficient traffic as the Querier is no longer responsible for the multicast traffic alone.

[008] For example, the method may include identifying multicast groups that are associated with the first network, allocating one of said multicast groups to a selected one of said plurality of forwarding apparatus such that multicast traffic designated to said multicast group is forwarded through said selected one of said plurality of forwarding apparatus.

[009] For example, the method may include identifying said multicast groups with reference to their corresponding group addresses.

[0010] The method may be implemented as a network switching apparatus which connects the first network to the second network.

[001 1 ] Therefore, there is disclosed a network switching apparatus comprising a processor, a first network interface comprising a first network port for exchanging data with a first network, a second network interface comprising a plurality of second network ports for exchanging data with a second network, and a processor to process multicast traffic between the first network and the second network, wherein the network switching apparatus is to distribute multicast traffic designated to multicast groups among said plurality of second network ports. The processor is configured to execute machine readable instructions to facilitate distribution of the multicast traffic. In an example, the networks switching apparatus may have a module for traffic distribution; this module may be implemented by a processor

[0012] In an example, the processor is adapted to identify multicast groups that are associated with the first network, and to allocate one of said multicast groups to a selected one of said plurality of second network ports such that multicast traffic designated to said multicast group is forwarded through said selected one of said plurality of second network ports.

[0013] The processor may be adapted to collect identification information of the multicast groups and to send the identification information of a multicast group to the „

4 selected one of said plurality of second network ports corresponding to said multicast group.

[0014] The processor may be adapted to collect identification information of the multicast groups from IGMP (Internet Group Management Protocol) Reports by making IGMP inquiries.

[0015] The processor may allocate said multicast groups among said plurality of second network ports to facilitate a more balanced or even traffic distribution among said plurality of second network ports.

[0016] The processor may send instructions to the second network interface to instruct all switching devices connected thereto to cease making IGMP queries upon receipt of an IGMP Snooping (IGSP)IGSP enabling message at the first network interface.

[0017] For example, the processor may switch to elect a Querier upon receipt of notification that IGSP is disabled in layer 2. [0018] There is disclosed a network switching apparatus comprising a first network interface for exchanging data with a first network, a second network interface for exchanging data with a second network, and a processor to process multicast traffic between the first network and the second network, wherein the processor is to cease electing a Querier upon receipt of notification of IGSP enabling. [0019] The schematic diagram of Figure 1 depicts a network switching apparatus 100 which connects an example local area network (LAN) 10 and the IP network 40.

[0020] The example LAN 10 includes a first host apparatus 12 (Host_A), a second host apparatus 14 (Host_B), a third host apparatus 16 (Host_C), and a fourth host apparatus 18 (Host_D). The host apparatus 12, 14, 16, 18 are connected to the network switching apparatus 100, and the network switching apparatus 100 is to facilitate data exchange between host apparatus of the LAN 10 and host apparatus outside the LAN 10. The network switching apparatus 100 is connected to the IP network 40 via three routers, namely, Router_A, Router_B and Router_C. [0021 ] The network switching apparatus 100 comprises a processor 102, a memory 104, a LAN interface 106, and a router interface 108 as depicted in Figure 2. Both the LAN interface 106 and the router interface 108 are Ethernet ports but are so designated for convenience. The LAN interface 106 includes a LAN port for connection with a private network to facilitate data exchange with the private network. The router interface 108 includes a number of router ports for connection with a corresponding number of routers. The processor 102 is to control and distribute data traffic between the LAN interface 106 and the router interface 108. The processor is configured to execute machine readable instructions to facilitate distribution of the multicast traffic. In an example, the networks switching apparatus may have a module for traffic distribution. The memory 104 is for saving information such as multicast membership, multicast group address, and traffic distribution routing information.

[0022] The router interface incudes a first port, Port_1 , a second port, Port_2, and a third port, Port_3. In the example network of Figure 1 , Port_1 is connected to Router A, Port_2 is connected to Router B, and Port_3 is connected to Router C. Each one of the routers, namely, Router A 42, Router B 44 and Router C 46 is an interfacing gateway between the LAN 10 and the IP network 40. In other words, each of the routers, namely, routers A, B, C, is a last hop router for data traffic coming from the IP network to the LAN or a first hop router for data going from the LAN to the IP network.

[0023] Each of the routers is a multicast router which supports multicast operation. Each multicast router is to perform two main functions, namely, multicast routing and multicast forwarding. Multicast routing is a process to set up a distribution tree for a multicast group. This process includes setting up multicast routing tables. A routing table may list multiple next hop addresses for a routing table entry. Multicast forwarding includes processing of an incoming datagram, the routing table lookup and transmission on an outgoing interface. A multicast router conserves network bandwidth by forwarding a single stream of datagrams to multicast group members who share the same data paths. A multicast router will replicate multicast datagrams where data paths begin to diverge. _Λ

6

[0024] A multicast group is open and dynamic. A host apparatus can join or leave a multicast group as a multicast group member at any time. When a host apparatus joins a multicast group, the host apparatus will inform the network switching apparatus 100 that it wishes to receive datagram addressed to that multicast group by sending a report message to the network switching apparatus 100. The network switching apparatus 100 will send report messages received from the host apparatus to the routers 42, 44, 46. The report messages are sent in a distributed manner so that the report messages will not go to a single router but may be distributed among the active routers in order to facilitate traffic load balancing. For example, the processor of the network switching apparatus 100 may distribute the load traffic by performing a hash operation on the multicast group addresses so that data traffic designated to a specific multicast group will be designated to a specific router for forwarding in order to facilitate load balancing. After the hashing operation has been performed, data traffic designated to a specific multicast group may be forwarded via a specific router to achieve traffic balancing. The report messages may be sent to the routers in a balanced manner so that the load at the routers is more balanced. The distribution may be by hashing, by sequential allocation, by distribution according to load requirements of the multicast groups, or by hashing with reference to group addresses to achieve a more balanced traffic distribution. [0025] The network switching apparatus 100 will periodically query the LAN to determine if known group members are still alive as a group member and will update its routing table according to results of the query. When a new router is connected to the network switching apparatus 100 to operate as a new multicast router, the router will send a query message and the network switching apparatus 100 on detecting the presence of a new multicast router will perform another operation to redistribute data traffic among the active multicast routers connected to the network switching apparatus 100; for example by performing another hashing operation.

[0026] Example multicast operation is illustrated herein with reference to the example network of Figure 1 and protocols relevant to the implementation of multicast operation. The protocols include, for example, Internet Group Management Protocol (IGMP), Multicast Listener Discovery Protocol (MLD), Protocol Independent Multicast (PIM) and Internet Group Management Protocol Snooping (IGSP) IGMP version 1 (RFC-1 1 12), IGMP version 2 (RFC-2236), IGMP version 3 (RFC-3376), MLD (RFC- 2710), PIM-SM (RFC-4601 ), PIM (RFC-4608) and IGSP (RFC-4541 ). The protocols are incorporated herein by reference and appropriate modifications are made where context requires to facilitate illustration of the present disclosure. [0027] Each multicast group is assigned a multicast group address in the range of 224.0.0.0 to 239.255.255.255 to facilitate multicast operation. This address range corresponds to Class D address in the class-based IP address scheme and each of the multicast group addresses start with "1 1 10" and this leaves 28 bits in the address field to identify a multicast group. [0028] A new IGMP message is defined. As depicted in Fig 7, when IGSP or IGMP Snooping is enabled at layer 2 in step 710, all ports of the LAN will be informed that the layer 2 IGSP has been enabled in step 720. When the layer 2 IGSP has learned a new router port, it will notify that port of the information that layer 2 has been IGSP enabled in step 730. [0029] When the layer 3 side of the network switching apparatus 100 has learned that IGSP has been enabled at layer 2, election of IGMP Querier will be cancelled, and Non-Queriers will delete information on the current Querier. The Non-Queriers will resume sending General Query messages periodically to its attached network to solicit group membership information while the Querier will continue to periodically send General Query messages periodically to its attached network to solicit group membership information.

[0030] When a new IGMP router is connected to the network, it will transmit an IGMP Query message. When the layer 2 IGSP has learned a new router, it will notify the new router that layer 2 has been IGSP enabled so that the router is made aware of the existence of layer 2 IGSP. There is no need for the new router does to activate IGMP Querier election mechanism.

[0031 ] When IGSP is disabled on the VLAN, layer 2 IGSP apparatus will notify all ports of the VLAN that IGSP has been disabled. When layer 3 IGMP routers receive the notification that IGSP has been disabled at layer 2, election of an IGMP Querier will resume. [0032] When layer 2 IGSP apparatus are present and notified of layer 2 IGSP enabling, IGMP multicast routers connected to common or shared network segments will no longer elect IGMP Querier. Therefore, there is no distinction between Querier and non-Querier. All IGMP routers will periodically transmit General Query messages to the common or shared network segments.

[0033] In the example network of Figure 1 , each one of the multicast routers, namely, Router_A, Router_B and Router_C, will periodically transmit IGMP Query messages. When the multicast router receive IGMP Report from the downstream hosts, it will set up an IGMP Group table, send requests to be added upstream, and forward multicast datagram downstream.

[0034] The Layer 2 switching apparatus will operate to perform IGMP Snooping. When an IGMP General Query message has been received, it will add a new corresponding port as a router port and refresh or update an aging timer. A first IGMP General Query message received within a Query period will be forwarded to other ports of the VLAN. A subsequent or non-first IGMP General Query message received within a Query period will not be be forwarded but will be used to maintain an aging timer. In the example network of Figure 1 , IGSP will learn that Router_A, Router_B and Router_C are multicast router ports.

[0035] When the Layer 2 switching apparatus has received an IGMP Report messages, it will add a corresponding port as a group member port and refresh or update an aging timer. A first IGMP Report message received by the network switching apparatus 100 within a Query period will be forwarded to a designated multicast router port.

[0036] In order to facilitate a more balanced multicast traffic distribution among available multicast routers, a multicast traffic distribution mechanism is adopted. An example multicast traffic distribution mechanism is to allocate multicast traffic designated to a multicast group address to be forwarded by a designated router such that multicast traffic for different multicast groups are shared by the available multicast routers. [0037] In an example, data such as multicast group addresses and indexes relating to the router ports which are gathered from IGMP Report messages are used as _Λ

9 parameters to balance load distribution by a hash function. For a multicast group address, hash values calculated from the available router ports are compared and the router port have a larger hash value is chosen as a forwarding port for that multicast group. Where hash values are identical, a routing port having a larger index will be selected as the forwarding port. The aforesaid port assignment rules will allocate a unique or definitive routing port among the plurality of available routing ports to a multicast group having a specific multicast group address. As multicast traffic are distributed among available routers, no single router will be burdened with forwarding of all multicast traffic. [0038] An example allocation of routing ports according to the multicast group addresses by performing a hash function is depicted in table 1 below.

Table 1

[0039] It will be noted from the above allocation that multicast traffic is allocated to the available ports according to multicast group addresses and this will result in a more even or balanced traffic distribution.

[0040] For example, when IGSP Reports of multicast groups having group addresses 225.0.0.0, 225.0.0.2, and 225.0.0.7, are received, the IGSP apparatus will only forward these group addresses to Router_A according to the hash table, and Router_A will be the only multicast router that is responsible for the maintenance of these multicast groups. In addition, Router_A will send the message (^*,G) to RP (Rendezvous Point), the message (S,G) to source and send traffic addressed to these multicast groups downstream. The symbols, RP, (^*,G), and (S,G) are as described in PIM-SM (rfc-4601 ). , _Λ

10

[0041 ] Likewise, when IGSP Reports of multicast groups having group addresses 225.0.0.1 , 225.0.0.4, and 225.0.0.5, are received, the IGSP apparatus will only forward these group addresses to Router_B according to the hash table, and Router_B will be the only multicast router that is responsible for the maintenance of these multicast groups. In addition, Router_B will send the message (^*,G) to RP, the message (S,G) to source and send traffic addressed to these multicast groups downstream.

[0042] Likewise, when IGSP Reports of multicast groups having group addresses 225.0.0.3, 225.0.0.6 are received, the IGSP apparatus will only forward these group addresses to Router_C according to the hash table, and Router_C will be the only multicast router that is responsible for the maintenance of these multicast groups. In addition, Router_C will send the message (^*,G) to RP, the message (S,G) to source and send traffic addressed to these multicast groups downstream.

[0043] An example process to facilitate multicast traffic distribution is described with reference to the flow chart of Figure 5. Initially, IGSP is enabled in layer 2 & information on IGSP enabling is disseminated in VLAN (layer 2) at step 410. IGSP is then to disseminate information of IGSP enabling on VLAN on learning new router ports at step 420. IGMP is then to cancel election of Querier on learning IGSP enabling in layer 2, and to send and receive periodic Query messages with no suppression of querying at step 430. IGSP will then maintain router ports on receipt of IGMP Query messages and forward the Query messages to corresponding router ports at step 440. Next, IGSP is to maintain host ports on receipt of IGMP Query messages and forward the Query messages to router ports according to hash values at step 450. IGSP is then to forward IGMP Reports in a balanced manner to upstream IGMP routers at step 460. IGMP to maintain IGMP Group, to send join-in messages upstream and to send multicast traffic downstream at step 470.

[0044] In an example, the LAN interface portion of the network switching apparatus 100 of Figure 2 is to operate as a Layer 2 switching apparatus while the IP network interface portion of the network switching apparatus 100 is to operate as a Layer 3 switching apparatus in this disclosure. , ,

1 1

[0045] In an example as depicted in Figure 6, the network switching apparatus is switchable to IGMP operation such as that according to in rfc 2236 by disabling IGSP at the VLAN in which case election of a router as a Queries will be resumed. For example, IGSP will be disabled in layer 2 at step 510. Information on IGSP disabling will be disseminated in VLAN (layer 2) at step 520. IGMP will resume election of Querier on learning IGSP disabling in layer 2 at step 530. IGMP operation will be resumed and a multicast router having the smallest IP address will elected as a Querier at step 540.

[0046] While the disclosure has been illustrated with reference to the above examples, it should be appreciated that the examples are for illustration only and are not to be construed as to restrict scope of the disclosure. For example, while various standard protocols such as IGMP, IGSP, PIM, have been used herein, they are used for convenience only. Furthermore, where an apparatus comprising a processor is described, it should be appreciated that the processor can be a single processor, multiple processors, a cluster of processors, or distributed processors without loss of generality. Where a method or process is described herein, it should be appreciated that the method or process can be implemented by means of hardware, software, firmware or a combination thereof without loss of generality.

Claims

A network switching apparatus according to Claim 1 , wherein the processor is to identify multicast groups that are associated with the first network, and to allocate one of said multicast groups to a selected one of said plurality of second network ports such that multicast traffic designated to said multicast group is forwarded through said selected one of said plurality of second network ports.

A network switching apparatus according to Claims 1 , wherein the processor is to identify said multicast groups with reference to their corresponding group addresses.

A network switching apparatus according to claim 1 , wherein the processor is to collect identification information of the multicast groups and to send the identification information of a multicast group to the selected one of said plurality of second network ports corresponding to said multicast group.

A network switching apparatus according to Claim 4, wherein the processor is to collect identification information of the multicast groups from IGMP Reports by making IGMP inquiries.

A network switching apparatus according to claim 1 , wherein the processor is to allocate said multicast groups among said plurality of second network ports to facilitate a more balanced or even traffic distribution among said plurality of second network ports.

7. A network switching apparatus according to clainn 1 , wherein the second network ports are ports adapted to connect to multicast routers.

8. A network switching apparatus according to clainn 1 , wherein the processor is to allocate said multicast groups to said plurality of second network ports by hashing.

9. A network switching apparatus according to Claim 8, wherein the processor is to use addresses of the multicast groups and indexes of the second network ports as hashing parameters.

10. A network switching apparatus according to claim 1 , wherein the processor is to receive IGMP (Internet Group Management Protocol) membership reports at the first network interface whereby the membership identifications of group members belonging to the multicast group are collected, and to distribute the membership reports among said plurality of second network ports such that the membership identification of a group member is available as a membership report of that group member on a selected port.

1 1 . A network switching apparatus according to Claim 10, wherein the processor is to send instructions to the second network interface to instruct all switching devices connected thereto to cease making IGMP queries upon receipt of an IGSP enabling message at the first network interface. 12. A network switching apparatus according to claim 1 , wherein the processor is to switch to elect a Querier upon receipt of notification that IGSP is disabled.

13. A network switching apparatus according to claim 1 , wherein the first network is a private network such as a VLAN and the second network is a public network such as the Internet. 14. A network switching apparatus according to Claim 1 , wherein the apparatus is a multicast router and the processor is to selectively forward multicast traffic to multicast groups selected among a plurality of multicast groups designated to the first network.

15. A method of forwarding multicast traffic to a network which is accessible through a plurality of forwarding apparatus, the method comprising allocating the multicast traffic among said plurality of forwarding apparatus according to a predetermined allocation scheme.