- The Evolution of MPLS
- In Search of a Faster Routing Method
- Many IP/Tag Switching Technologies
- Introducing MPLS
- Back to Fundamentals
Many IP/Tag Switching Technologies
The first proposal for IP switching (RFC 1953) was introduced in early 1996 by a small startup company called Ipsilon Networks. It proposed the prior mapping of IPv4 flows onto a Layer 2 label space; more specifically, onto the ATM VPI/VCI fields, as they were readily available.
The idea of IP switching prompted a flurry of proposals along a similar line of thought. Among them were Cisco's Tag Switching, IBM's ARIS (Aggregate Route-Based IP Switching), Cascade's IP Navigator, and Toshiba's Cell Switch Router.
Cisco proposed Tag Switching (RFC 2105) in early 1997. A generic "shim" header is used to encode a tag that has only local significance (unlike the IP address, which has global significance). In addition, a separate control mechanism was proposed to distribute the tag information among the switches. Again, the tag could be mapped onto the ATM VPI/VCI field when the underlying Layer 2 infrastructures were ATM.
Although their details vary slightly, all the proposals had the same essential ingredients. It's therefore natural to have a standardized method on which everyone can agree, and that presumably would combine the advantages (or disadvantages) of various proposals.