MULTIHOMING IN MOBILE IPv6. By: Rajat Singh Ahmed Abdul Haleem

Transcription

1 MULTIHOMING IN MOBILE IPv6 By: Rajat Singh Ahmed Abdul Haleem

2 Definition of multihoming: A host can be multihomed in two basic ways: The first is with a single network interface, which has been assigned multiple IP addresses The second is multiple network interfaces. 2

3 Scenarios in which a host is multihomed 3

4 Only one interface One HoA,, one CoA: The host is not multihomed Several HoAs,, one CoA: The host is multihomed, since it has several HoAs. 4

5 Only one interface Several HoAs,, one CoA (contd.): This case may happen when a host is getting access to Internet through different ISPs and each offers a Mobile IPv6 service to the host. That way, the host will have a HoA per ISP. Once the host is connected to a visited IPv6 subnet, it gets one CoA. This CoA may be registered with all the Home Agents provided by the ISPs, in order to remain simulteneously reachable through all its HoAs. 5

6 Only one interface One HoA,, several CoAs: The host is multihomed since it has several CoAs. This case may occur when the interface of the host is connected to a link where multiple IPv6 prefixes are advertised. Several HoAs and several CoAs: The host is multihomed, since it has multiple addresses. This case can be viewed as a combination of the two cases described above 6

7 Multiple Interfaces One HoA, one CoA The host is multihomed. Example: A host with two interfaces connected to different IPv6 subnets; one of the subnet is the home network of the host and allows the host to use its HoA. The host can build a temporary IPv6 address on its other interface but it cannot register the temporary address with its Home Agent. 7

8 Multiple Interfaces One HoA, several CoAs The host is multihomed. Example: Consider a host with several interfaces, each connected to an IPv6 network (the same or not). In this example, at least one IPv6 address is configured on each interface. The host has only one home link, and only one Home Agent. 8

9 Multiple Interfaces Several HoA, one CoA The host is multihomed. This case extends the case (n,1,1) when the host has several HoAs, for example from multiple ISPs. Several HoAs, several CoAs The host is multihomed. Example: Consider a host with three interfaces, two of them connected to their home link(two different HoAs) and the last one connected to a visited link where two IPv6 prefixes are advertised. 9

10 Goals & Benefits of multihoming: ubiquitous access: anywhere and anytime redundancy/fault recovery load sharing: share load in the network load balancing: share load between interfaces 10

11 Goals & Benefits of multihoming: Bicasting: n-cat the traffic to multiple addresses preferences settings: allow the user/application/isp to set preferences on interfaces/addresses 11

12 Open issues Issues related to MIPV6 In case of multiple HoAs when the mobile host otains a new CoA, it's not clear to which HoA the new CoA would be bound to. There is thus a need to define a relationship between HoAs and CoAs. How to bind multiple CoAs to the same HoA Need a policy to manage several CoAs bound to a single HoA 12

13 Open issues Issues not related to MIPV6 How to simultaneously use several interfaces How to bind multiple HoAs to host 13

14 Open issues Issues not related to MIPV6 In the (n,1,1) case, the node may want to use each interface differently according to some policies and preferences that would define which flow would be mapped to which interface and/or which flow should not be used over a given interface. Solution: Allow multihomed hosts to set filters on flows on distant nodes (Correspondent Node or Home Agent). 14

15 Multihoming Scenarios with Multiple Home Agents in Mobile IPv6 15

16 Multihoming scenarios Basic scenarios - multiple HAs within a single AS Extended scenarios - multiple HAs in different AS 1. Multiple HAs in different AS with one HoA 2. Multiple HAs in different AS with multiple HoAs 16

17 Assumptions: (Assumption 1) MN accesses multiple HAs using a single IP addresses: (Assumption 2) MN has only one active CoA at a time: (Assumption 3) There exist trust relations among HAs: 17

18 Basic multihoming scenario - multiple HAs within a single AS The basic scenario considers the case that MN is multihomed to multiple HAs in different home links within a single AS. The goal of this multihoming configuration is to provide HA redundancy for MN. 18

19 An example of basic multihoming scenario 19

20 Benefit of the basic multihoming scenario We can reduce the burden of MN to maintain the HA list and SA database. How? Since the MN can access multiple HAs using one HA address and multiple HAs share SAs,, the MN does not have to maintain HA list to track HAs who have its binding information and SA information.if the MN should establish SA with each HA, the burden to manage SA database would increase. 20

21 Technical issues in implementing basic scenario Inconsistent IPsec sequence number Inter-HA protocol -Synchronizing binding information -Synchronizing SA information -HA failure detection and recovery 21

22 Inconsistent IPsec sequence number Defination: The The IPsec sequence number is an unsigned 32-bit counter which monotonically increments by one for each IPsec packet. This field is mandatory and always present even if the anti-replay service for a specific SA is disabled. 22

23 Inconsistent IPsec sequence number Problem: If multiple HAs are allowed to share the same SA, it is difficult to synchronize IPsec sequence number among tunneled packets by them. 23

24 Inconsistent IPsec sequence number Proposed solution: To cope with inconsistent To cope with inconsistent IPsec sequence number among multiple senders: We provide additional information, the original IP address of HA. All HAs are accessible from MN using the reserved HA address, but each HA should have its original IP address to be attached to the home link. Each HA who shares the same SA adds its original IP address information to the destination option header in the outer header of tunneled packet. To do this, we define the ORIGIN_IP destination option. 24

25 Inconsistent IPsec sequence number Proposed solution(contd.): When MN receives the inbound tunneled packets, it checks the ORIGIN_IP option in the destination option header to extract the original ip address of the sender HA. Based on the original HA address, the MN can split the IPsec tunneled streams into an individual stream from each HA. 25

26 Inter-HA protocol 1. Synchronizing binding information There are two possible ways in synchronizing binding information. i) HA can request Binding Cache information for a specific MN to its primary HA. ii) The second is that the primary HA for a specific MN sends out the Binding Information Update message to other HAs on the HA list whenever there is the change in its Binding Information Cache. 26

27 Inter-HA protocol Synchronizing SA information: The procedure of synchronizing SA information is very similar to that of binding information except it requires an additional SA Information renew request message. HA can request the SA information for a specific MN to the primary HA using the SA information request message. On the other hand, HA can send out the SA Information update message in the same manner as the Binding Information update message when there is the change in SA Information for a specific MN by reestablishing SA due to SA revocation or expiration. 27

28 Inter-HA protocol HA failure detection and recovery: There are two possible methods to detect HA failure. i) HA can detect the failure of other HAs by sending an application-level level keepalive message to other HAs on a regular basis. If an HA does not respond to these messages consecutively, the sender HA of this message marks the HA entry as invalid. 28

29 Inter-HA protocol HA failure detection and recovery: ii) The second method is to use the HA HELLO message. HA regularly sends out these HA HELLO messages to inform other HAs of activeness of the sender HA of these messages. So, if an HA does not receive these message several times in a row, it marks the HA entry as invalid. 29

30 Multiple HAs in different AS with one HoA 30

31 Multiple HAs in different AS with one HoA Benefit: The inbound traffic to the MN is always going to be the cheapest HA according to the BGP policy of the CN domain. The technical issue: multiple multiple ASs should advertise the same network prefix for MN's home link. 31

32 Multiple HAs in different AS with multiple HoAs: This scenario is the typical example of site- multihoming. This scenario is likely that we have the combination of multiple basic scenario. Since HAs within an AS do not interfere with those in other AS, no change in the basic scenario is required. 32

33 Conclusion So, we have seen many issues related to multihoming and studied different scenrios in which a host is multihomed. But still there are a number of issues where a good solution is yet to be proposed. 33

34 References N. Montavont: Analsis of Multihoming in Mobile IPv6,, IETF Internet Draft, work in progress: draft-montavont montavont-mobileip-pb-statement-01.txt, July SeungSun Hong et al: Multihoming Scenrios with Multiple Home Agents in Mobile IPv6,, IETF Internet Draft, work in progress: draft-honig honig- mip6-multihoming multihoming-scenarios-00.txt, July

35 Questions? 35