The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: Penultimate Hop Popping
Hi Bhavesh, Regardless of how the next hop is represented, the egress would need to be capable of two lookups if there is a non-null label present that results in a pop operation, and there is additional information to determine next hop (IP header or other field as you suggest). The benefits of non-PHP implementation is that the label specific information and statistical information is maintained for one-hop LSPs and last hop of an LSP. This is not an unsolvable problem as Avici hardware and software is capable of these two lookups, as well as operation in a PHP scenario. Don > On Fri, Aug 29, 2003 at 10:24:22PM +0530, Bhavesh Modi wrote: >> >> Hi all >> >> As RFC 3031 says ( Section 3.16 ), If we do not use Penultimate Hop >> Popping , the egress router will have to do two table lookups even in >> case of only single label in label stack - one for determinig that it >> has to pop the label & second traditional IP lookup. But instead of >> only telling to pop the label can't we have one more field which gives >> it next hop? If we have such thing, there is no need of penultimate >> hop popping in case of stack of sigle label atleast. Has any vendor >> implemented such technique? > > What you're talking about is replacing explicit-null with a real label > value. This is an implementation-specific thing at the tail; simply > advertise a non-null, real label for a given prefix or next-hop or > whatever. One of the problems with this approach is dealing with the > payload of whatever's underneath this bottom label without looking at > the payload. > > > > > eric > >> >> -Bhavesh Modi >> MTech-ICT >> DA-IICT. >> Gandhinagar >> >> ------- >> The MPLS-OPS Mailing List >> Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml >> Archive: http://www.mplsrc.com/mpls-ops_archive.shtml > > ------- > The MPLS-OPS Mailing List > Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml > Archive: http://www.mplsrc.com/mpls-ops_archive.shtml ------- The MPLS-OPS Mailing List Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml Archive: http://www.mplsrc.com/mpls-ops_archive.shtml
|
|