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NAT State Synchronization using SCSP draft-xu-nat-state-sync-00

NAT State Synchronization using SCSP draft-xu-nat-state-sync-00. Dean Cheng (chengd@huawei.com) Xiaohu Xu (xuxh@huawei.com) Joel Halpern (Joel.Halpern@ericsson.com) Mohamed Boucadair (mohamed.boucadair@orange-ftgroup.com) IETF76, Hiroshima. SCSP – A Protocol for Data Cache Synchronization.

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NAT State Synchronization using SCSP draft-xu-nat-state-sync-00

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  1. NAT State Synchronization using SCSPdraft-xu-nat-state-sync-00 Dean Cheng (chengd@huawei.com) Xiaohu Xu (xuxh@huawei.com) Joel Halpern (Joel.Halpern@ericsson.com) Mohamed Boucadair (mohamed.boucadair@orange-ftgroup.com) IETF76, Hiroshima

  2. SCSP – A Protocol for Data Cache Synchronization • Server Cache Synchronization Protocol (SCSP - RFC2334) solves a general server synchronization/cache-replication problem for distributed databases. • SCSP uses link-state based algorithm to reliably flood database entries among participating servers. • SCSP defines application-independent protocol mechanisms and requires applications to define their own formats for cache records, called Cache State Advertisement (CSA). • This document specifies a method of using SCSP to achieve NAT state synchronization among NAT devices in a redundancy group including associated CSA format.

  3. Requirements for NAT Devices Deployed with Redundancy • Achieve hot-standby and load balancing, data synchronization is a MUST. • Reliability and robustness are very much desired during data synchronization process. • Stateful contents in data cache maintained by NAT MUST be replicated and synchronized on all participating NAT devices in a redundancy group. • When a NAT device in a redundancy group fails, all existing NAT sessions must survive without any perceived impact on traffic (e.g., severe delay, loss, etc.)

  4. Use SCSP to Sync NAT Database • Multiple NAT devices deployed on the border between two IP domains form a redundancy group which, possibly along with other redundancy groups, belong to a SCSP Server Group (SG), identified by SGID. • Within a redundancy group, there is a primary and one or more backup devices. When the primary NAT device fails, a new primary NAT device is elected. • For each NAT type, a separate SCSP Protocol ID (PID) is assigned by IANA. • Currently NAT type includes NAT44, NAT64, and NAT46. • The method described is applicable to stateful NAT devices only.

  5. NAT State Refreshment Mechanism • Only primary NAT device can create new cache entries. • NAT database entries are aged. The primary device is responsible to re-originate and re-flood them before aging out for active entries. • After a switchover, the newly elected primary NAT device MUST re-originate all cache entries that were originated by the previous primary NAT device, with NAT contents remain the same followed by a reliable flooding defined by SCSP.

  6. SCSP Message Mandatory Common Part • 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol ID | Server Group ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender ID Len | Recvr ID Len | Number of Records | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / Sender ID (Variable Length) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / Receiver ID (Variable Length) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  7. Values for the SCSP “Mandatory Common Part” • Protocol ID = TBD • There is a separate Protocol ID for NAT44, NAT64, and NAT46, assigned by IANA. • Server Group ID = NAT device redundancy group ID • Sender ID Len • = 4, if IPv4 address is used • =16, if IPv6 address is used. • Per RFC2334, an identifier assigned to a server (in this case, a NAT device), might be the protocol address of the sending server. • Recvr ID Len • = 4, if IPv4 address is used • =16, if IPv6 address is used. • Per RFC2334, an identifier assigned to a server (in this case, a NAT device), might be the protocol address of the receiving server.

  8. Values for the SCSP “CSAS Record” • Cache Key Len = 4 • This 4-byte opaque string is generated by the NAT device that originates the CSAS. • Originator ID Len • = 4, if IPv4 address is used • = 16, if IPv6 address is used. • Per RFC2334, an identifier assigned to a server (in this case, a NAT device) might be the protocol address of the server.

  9. NAT Specific CSA • 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol | Option Length | Unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Port Mapped from | Port Mapped to | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / Address Mapped from (Specific to NAT type) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / Address Mapped to (Specific to NAT type) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / TLV Options (Variable Length) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  10. The Next … • Authors would like to solicit comments with discussion on mailing list at this time • If there is enough interest, we’ll propose to move this I-D as a working group document

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