Consider the CID to be a connection
identifier equivalent to a particular Ethernet wire in an Ethernet network.
In that context read:
“Thanks for your
reply.I agree CID's are used for forwarding packets,but in MAC header we have
only one CID field,is that CID indicates source CID or destination CID.”
As being
“Thanks for your reply.I agree Ethernet wires are used
for forwarding packets,but carrying the packet we have only one wire ,
does that wire indicate the source port or destination port?”
So to answer case b, the CID doesn’t
identify the source, it identifies both the transmitter and receiver (SS and
BS). The BS will receive the packet because it has knowledge that it is one end
of the connection with that CID and it forwards traffic based on the contents
of the payload, not the CID. If the payload contains and 802.1 compliant header
information (the Ethernet or 802.1 packet CSs) then it will use the mac address
to have it routed through an 802.1 bridge or terminate it into an IP stack that
will either route it or terminate it. If the payload contains just an IP packet
(IP packet CS) then it will pass up into an IP stack.
Case a is misstated. At L1 we have a point
to multipoint system, but at L2, we don’t have a point to multipoint
system, we have multiple point to point connections. In all cases, the CID get
the packet from SS to BS or BS to SS, but the payload contents determine the
final destination of the packet.
This is different to 802.11, where the MAC
address is used for directing the packet, hence there are 3 and 4 address
packets so the sender and transmitter and receiver and destination can be distinguished.
I hope that helps.
DJ
From: Vasanth.Rajan
[mailto:vasantha.rajan@CRANESSOFTWARE.COM]
Sent: Wednesday, June 21, 2006
9:52 PM
To: STDS-802-16@listserv.ieee.org
Subject: Re: [STDS-802-16]
destination address
Thanks for your reply.I agree CID's are used for forwarding
packets,but in MAC header we have only one CID field,is that CID indicates
source CID or destination CID.
a.In a point to multipoint system if the CID in MAC
header indicates destination then how come the SS's come to know other
SS's CID and how come the BS come to know the source CID sending that
packet.
b.If the CID indicates source CID then how come the BS will
forward the packet to the destination SS.
Please help me in sorting out this issue
----- Original Message -----
Sent: Wednesday, June
21, 2006 11:23 PM
Subject: RE: [STDS-802-16]
destination address
In 802.16 the MAC addresses are not the
basis for forwarding packets. Instead CIDs are used. These can be unicast,
multicast or broadcast.
From:
Vasanth.Rajan [mailto:vasantha.rajan@CRANESSOFTWARE.COM]
Sent: Wednesday, June 21, 2006
7:01 AM
To: STDS-802-16@listserv.ieee.org
Subject: [STDS-802-16] destination
address
In 802.16 point to multipoint, if a subscriber station(SS1)
needs to send a packet to another subscriber station(SS2) then,how does
a SS1 comes to know the destination address(b'coz in 802.11 MAC header we
have source MAC address & destination MAC address fields.)