Subject: question: data link destination address

From: Gerhard Gessler <[email-masked]>
Date: Tue, 24 Nov 1998 14:43:15 +0100

Hi everybody,

my name is Gerhard Gessler, I study electrical engineering and
information technology at the Munich University of Technology and am
currently working on my dissertation. For that I´m implementing PIM-DM
over IPv6 (into the kernel of WinNT) and do some research about its
interaction with Mobile IPv6.

I have read the PIM-DM draft (draft-ietf-pim-v2-dm-01.txt), but I still
have some questions about PIM-DM and some addressing schemes.

I´m grateful for any help and comments.

If a sender (S) is attached to a multi-access-LAN (e.g. ethernet) with
two routers (R1, R2, look at the sketch) and a listening host (A) and it
wants to send mulicast-packets to a group, what data link destination
address does the sender use, what data link address do the routers R1
and R2 listen to, what data link address does A listen to?

               A     S      R1---other LANs/routers with hosts
               |     |      |
               ------+-------
               |
               R2
               ||
            other LANs/routers with hosts

       there is no possibility to create a loop between R1 and R2

  sender packet:
    data link source address:  its own ethernet unicast-address
    data link dest. address :  ????
    IP source address:      :  own IPv6 unicast-address
    IP destination address  :  the group address (a multicast address)

Thank you in advance for any reply and help.

  Gerhard

---------------------------------------------------
Gerhard Geßler

IABG mbH, Abteilung CC31
Einsteinstr. 20
85521 Ottobrunn

Tel. (089) 6088 3539
Fax: (089) 6088 2845

E-Mail: [email-masked]

---

From: Bill Fenner <[email-masked]>
Date: Wed, 25 Nov 1998 10:38:46 PST

In message <[email-masked]>you write:
>host (A) and it

Depends on the data link.  If it's Ethernet, then the IP group
address is mapped into an ethernet multicast address.  For IPv4,
the mapping in RFC1112 is used; for IPv6, the mapping is described
in RFC1972.

Routers must listen to the entire range of data link multicast
addresses; group members must listen to the set of addresses which
represent groups that have been joined by that host; senders need
not listen to any addresses (except for those covered by the previous
two categories, e.g. if the sender is also a group member).

  Bill