The MPLS WG Archive

[Bora Akyol <bora@cisco.com>]

MAC Address is 48 bits. You need a 32 bit identifer. I also don't think that POS
interfaces have unique HW identifiers.

Bora


"Abarbanel, Benjamin" wrote:

> Bora:
>   I would agree that there needs to be a management knob to specify
> interface
> IDs that are static for TE purposes. I recommend we use the interface
> hardware
> address, in most cases this number is either configured statically by
> management
> system or is burnt into the adopter port card (e.g. ethernet MAC address).
>
> So I would say that an unnumbered interface could be defined by its "IP
> Router ID"
> and its "hardware interface address". In most IP interfaces there is already
> a
> field assigned for the hardware interface address. Typically that field is
> reflected
> in the "ifr_hwaddr" field of the (struct ifreq) IP interface structure.
> Usually its a
> MAC address but it could be any interface type hardware address.
>
> Regards,
> Ben
>
> -----Original Message-----
> From: Bora Akyol [mailto:bora@cisco.com]
> Sent: Wednesday, November 07, 2001 1:35 PM
> To: Abarbanel, Benjamin
> Cc: mpls@UU.NET
> Subject: Re: changes to unnumbered and link bundling
>
> If the operator does not have control over the interface identifiers be it
> IP
> addr or a 32 bit identifier, then they should not be specifying it as part
> of
> the constraints.
>
> Ideally, there needs to be a management knob to specify interface
> identifiers
> for TE purposes statically.
>
> Bora
>
> "Abarbanel, Benjamin" wrote:
>
> > What I was refering to, is someone writes a script configuring constraints
> > for ERO
> > CSPF calculations, but is unable to predetermine the Interface identity
> > ahead of time
> > if it's defined by an Ifindex and router ID) as an unnumbered interface.
> > Since Ifindex
> > is dynamic in nature the script will fail if the router affected is
> > rebooted.
> >
> > Ben
> >
> > of that router. Normally
> > file containing
> >
> > -----Original Message-----
> > From: Bora Akyol [mailto:bora@cisco.com]
> > Sent: Tuesday, November 06, 2001 6:51 PM
> > To: Abarbanel, Benjamin
> > Cc: mpls@UU.NET
> > Subject: Re: changes to unnumbered and link bundling
> >
> > CSPF computation is based on the routing database obtained from the IGPs,
> if
> > interface identifiers change, the database will be updated.
> >
> > This is more of an imlementation specific question.
> >
> > Bora
> >
> > "Abarbanel, Benjamin" wrote:
> >
> > > Hi all:
> > >   I have one concern regarding the use of EROs and Router ID/Ifindex to
> > > define
> > > specific unnumbered interfaces in the network. Constraint routing
> usually
> > > defines certain constraints (for CSPF) calculation sake based on
> > interfaces
> > > identified via IP addresses the problem with identifying interfaces
> which
> > > are
> > > unnumberd with router ID and Ifindex is that the Ifindex is dynamic and
> > > changes
> > > within the scope of the router especially during a reconfig of the
> > interface
> > > or
> > > reboot of the router. If someone, in another router wanted to write
> > > a static CLI based script to specify certain Constraint policies on in
> > > interface
> > > that is unnumbered he/she could not do it based on a Ifindex, because he
> > > would not
> > > know its value or be able to predict it will have the same value through
> a
> > > reboot
> > > of the router.
> > >
> > > How do we solve this one folks?
> > >
> > > Ben
> > >
> > > -----Original Message-----
> > > From: Bora Akyol [mailto:bora@cisco.com]
> > > Sent: Tuesday, November 06, 2001 12:41 PM
> > > To: Nabil Seddigh; Yakov Rekhter
> > > Cc: mpls@UU.NET
> > > Subject: Re: changes to unnumbered and link bundling
> > >
> > > This is similar to the discussion we had on the expanded ERO issue
> > > (draft-akyol-mpls-expanded-ero-00.txt, now expired) a while ago. I
> concur
> > > with Yakov that one has to identify unnumbered interfaces by the tuple
> > > (Router ID, ifindex) where ifindex is some 32 bit quantity assigned by
> the
> > > router that is advertising this interface in the IGP TE advertisements.
> > >
> > > If one does sit on a broadcast media where a router may have multiple
> > > interfaces sitting on the same segment, then even the proposal below is
> > not
> > > sufficient to uniquely identify the full path specified by the ERO.
> > >
> > > As A1 uniquely identifies the egress interface out of A, but we can not
> > > identify (assuming that this is happening on an Ethernet segment where B
> > has
> > > multiple interfaces connected) which ingress interface of B we want to
> > use.
> > >
> > > Which is why I think, the best way to specify an ERO is to write
> > > Router ID, Egress Interface, Router ID, Ingress Interface
> > >
> > > This leaves pretty much nothing to "interpretation" and results in a
> > precise
> > > definition.
> > >
> > > If there is interest, I may revive the expanded ERO draft.
> > >
> > > Bora
> > >
> > > ----- Original Message -----
> > > From: Yakov Rekhter <yakov@juniper.net>
> > > To: Nabil Seddigh <nseddigh@tropicnetworks.com>
> > > Cc: <mpls@UU.NET>
> > > Sent: Tuesday, November 06, 2001 8:03 AM
> > > Subject: Re: changes to unnumbered and link bundling
> > >
> > > > Nabil,
> > > >
> > > > > The proposed change is not quite clearly stated. Can you please
> > > > > restate in more precise language. Is it possible to put a diagram
> > > > > in the draft? E.g if we have nodes A,B,C,D with unnumbered i/f
> > > > > 1-6 (I have made them distict for ease of illustration):
> > > > >
> > > > >       1       2   3          4   5      6
> > > > >     A --------- B ------------ C -------- D
> > > > >
> > > > > The language in Section 6 of the unnum-02 draft would appear to
> > > > > mandate an unnumbered ERO as follows: A1,B3,C5
> > > > >
> > > > > What are you proposing to change it to?
> > > > > Is it B1,C3,D5?
> > > >
> > > > Certainly not, as I am proposing that "The Interface ID is the
> interface
> > > > identifier assigned to the interface by the LSR specified by the
> router
> > > ID."
> > > >
> > > > With this in mind B1 is not a valid combination, as the interface
> > > > identifier 1 is assigned by A, not by B. And with my proposal
> > > > you can't put in the Unnumbered Interface subobject the
> > > > interface identifier assigned to the interface by one LSR, and
> > > > the router ID of some other LSR.
> > > >
> > > > Ditto for C3 and D5.
> > > >
> > > > Yakov.
> > > >
> > > > P.S. Just like a numbered interface on an LSR is identified by the
> > > > IP address that the LSR assigns to that interface, I am suggesting
> > > > that an unnumbered interface be identified by the identified
> > > > (i/f index) that the LSR assigns to that interface and the Router-ID
> > > > of the LSR itself.
> > > >