Re: [mpls-linux-devel] Jamal's MPLS design document

[Vilyan D. <vdi...@ne...>]

Hello,

I have comments on last e-mails here (general notes, not regarding 
current implementation).

First, what the FEC is?

RFC3031:

forwarding equivalence class   a group of IP packets which are
                                     forwarded in the same manner (e.g.,
                                     over the same path, with the same
                                     forwarding treatment)

Most commonly, a packet is assigned to a FEC based (completely or
partially) on its network layer destination address. However, the
label is never an encoding of that address.
--------------------------------------------------------------------------------------------------------

So, we are free to decide how to classify packets into FECs. We should 
use at least network layer destination
address - so called basic MPLS implementation.

Label binding are advertised to other LSRs via some label distriburion 
protocol. This protocol
should describe FECs to its neigbours. Currently LDP (RFC3036) supports 
3 types of FEC elements:
wildcard, host and prefix (IPv4 and IPv6).

Destination prefix only classification is implemented by many vendors. 
For example see NPF MPLS
Implementation Agreement.

In other hand draft-ietf-mpls-ftn-mib-09 defines more complex 
classification rules:

mplsFTNTable allows 6-tuple matching rules based on one or more of
   source address range, destination address range, source port range,
   destination port range, IPv4 Protocol field [RFC791] or IPv6 next-
   header field [RFC2460] and the DiffServ Code Point (DSCP, [RFC2474])
   to be specified. 

But I don't see support in label distribution protocols for such FEC 
elements.

Using only destination prefixes for classification will allow us to 
implement FTN table as extention of
IPv4/IPv6 FIB. In this case we don't need separate Classification Engine.

So, we should define classification rules.

> c) tunnels like IPSEC using the SPI mapped to an MPLS label
> d) L2 type of technologies ex VLAN, PPP, ATM etc

For transport of L2 frames we should use Pseudo Wires (see IETF PWE3 w.g. documents). We don't need
additional classification rules.


-- 
Regards,
Vilyan Dimitrov
Network Administrator
Net Is Sat Ltd.