Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
2000-07-31
2004-08-03
Hsu, Alpus H. (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S466000, C370S395520
Reexamination Certificate
active
06771662
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a node applied to an IP (Internet Protocol) network and, more particularly, to a label switching type packet forwarding apparatus.
(2) Description of the Related Art
On an IP network typified by the Internet, data is forwarded in accordance with the IP protocol. In recent years, attention is paid to a label switching type packet forwarding for labeling an IP packet and forwarding a reception packet in accordance with the label. A typical example of label switching is MPLS (Multi Protocol Label Switching) which is being standardized by the IETF (Internet Engineering Task Force).
In order to make the invention understood easily, a conventional technique related to the invention will be described hereinbelow with reference to drawings.
FIG. 20
shows an IP network comprising a plurality of routers R
51
to R
55
for forwarding IP packets.
Hosts IP
51
to IP
55
such as terminals or servers as sources or destinations of IP packets are connected to the IP network via the routers. In the IP network shown in the diagram, the router R
53
for connecting the routers R
51
, R
52
, R
54
and R
55
has, for example, a routing information table
100
shown in
FIG. 21
to determine the forwarding route of a reception packet.
The routing information table
100
comprises a plurality of entries showing the relation among a destination IP address IN
51
as input information IN
5
, a next hop router address IM
51
as intermediate information IM
5
, and output port identifier (output port number) OUT
51
and output layer
2
(L
2
) information OUT
52
as output information OUT
5
.
In the IP network of
FIG. 20
, for example, when a route of an IP packet transmitted from the host IP
51
to the host IP
53
is RT
51
and a route of an IP packet transmitted from the host IP
52
to the host IP
54
is RT
52
, entries EN
51
and EN
52
having the contents shown in
FIG. 21
are set in the routing information table
100
of the router R
53
in correspondence with the routes.
For example, when attention is paid to the route RT
51
, an IP packet inputted from the host IP
51
via the router R
51
to the router R
53
has an IP header H
1
of a format shown in
FIG. 22
, in which the address of the host IP
53
is set as an destination IP address H
13
. When the IP packet is received from the router R
51
, the router R
53
extracts the destination IP address from the IP header H
1
and searches the table
100
by using the destination IP address as input information. By the search, an output port number #
53
to which the IP packet is to be forwarded and output L
2
information
5
i
to be added to an output packet are obtained.
When the routing information table
100
is divided into a first table in which the relation between the input information IN
5
and the intermediate information IM
5
is defined and a second table in which the relation between the intermediate information IM
5
and the output information OUT
5
is defined, by referring to the second table on the basis of the next hop router address R
54
obtained from the first table, the output port #
53
and the output L
2
information
5
i
are obtained. When the input information IN
5
and the output information OUT
5
are directly associated with each other on the same table, the intermediate information IM
5
can be omitted.
The output L
2
information added to the output packet denotes routing information of the layer
2
(data link layer) of the OSI reference model applied to output lines of the router R
53
. For example, when the output line is of Ethernet, an MAC destination address H
21
in an Ethernet header H
2
shown in
FIG. 23
corresponds to the output L
2
information. When the output line is an ATM line, VPI/VCI H
31
in an ATM header H
3
shown in
FIG. 24
corresponds to the output L
2
information. When the output line is of POS (PPP over SONET) , as shown in
FIG. 31
, no information of the layer
2
exists in the POS header. Consequently, in a table entry corresponding to the POS line in the routing table
100
, the output L
2
information OUT
52
is blank.
The router
53
forwards the reception IP packet to the next hop router R
54
in a format that the output L
2
information which is necessary for a lower layer of the OSI standard model applied to each of the output lines is added. Also on the packet route RT
52
having the information of the destination IP address of “IP
54
”, in a manner similar to the route RT
51
, an IP packet is forwarded to the next hop router R
55
in accordance with the output information of the entry EN
52
corresponding to the destination IP address set in the routing information table
100
.
FIG. 25
shows an example of an IP network including label switching nodes E
61
to E
63
, C
61
and C
62
for forwarding packets by the MPLS.
In the diagram, an ellipse domain D
6
in the center of the network denotes an MPLS domain for forwarding packets by the MPLS. In the following description, the nodes E
61
, E
62
and E
63
disposed at the incoming and outgoing ports of the MPLS domain D
6
will be called edge nodes and the nodes C
61
and C
62
disposed on the inside of the MPLS domain will be called core nodes. The edge nodes E
61
, E
62
and E
63
are connected to routers R
61
, R
62
, R
63
and R
64
for IP forwarding the packets, respectively, on the outside of the MPLS domain D
6
.
On the inside of the MPLS domain D
6
, as shown in
FIG. 26
, the packet forwarding is performed in an MPLS packet
210
format in which a Shim header H
4
is added to an IP packet
200
. Each of the edge nodes has a table shown in
FIGS. 27 and 28
for determining the forwarding route of a reception packet.
FIG. 27
shows an ingress routing information table
110
which is referred to when the forwarding route of a packet inputted from the outside of the MPLS domain D
6
into the domain is determined.
FIG. 28
shows an egress routing information table
120
which is referred to when the forwarding route of a packet outgoing from the inside of the MPLS domain D
6
to the outside is determined.
The ingress routing information table
110
comprises a plurality of entries showing the relation between a destination IP address IN
61
as input information IN
6
i
, and an output port OUT
61
and an output label OUT
62
as output information OUT
6
i
. The output label OUT
62
corresponds to the value of a label H
41
included in the Shim header H
4
of the MPLS shown in FIG.
26
.
The egress routing information table
120
comprises a plurality of entries showing the relation among a destination IP address IN
62
as input information IN
6
e
, a next hop router address IM
61
as intermediate information IM
6
e
, and an output port OUT
63
and output L
2
information OUT
64
as output information OUT
6
e
. The egress routing information table
120
basically has a structure similar to that of the routing information table
100
shown in
FIG. 21
which is referred to in the IP forwarding.
In the IP network shown in
FIG. 25
, when it is assumed that a route of an IP packet transmitted from the host IP
61
to the host IP
63
is RT
61
, a route of an IP packet transmitted from the host IP
62
to the host IP
64
is RT
62
, a route of an IP packet transmitted from the host IP
63
to the host IP
61
opposite to the route RT
61
is RT
63
, and a route of an IP packet transmitted from the host IP
64
to the host IP
62
opposite to the route RT
62
is RT
64
, in the ingress and egress routing information tables
110
and
120
of the edge node E
61
, entries EN
61
, EN
62
, EN
63
and EN
64
having the contents shown in
FIGS. 27 and 28
are set in correspondence with the routes.
When attention is paid to the route RT
61
, the IP packet transmitted by the host IP
61
to the host IP
63
is inputted to the edge node E
61
via the router R
61
. The edge node E
61
searches the ingress routing information table
120
by using the destination IP address “
1
IP
63
” of the reception IP packet as input information and obtains output port number
Miki Kazuho
Sakamoto Ken'ichi
Wakayama Koji
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Hsu Alpus H.
Tran Thien
LandOfFree
Label switching type of packet forwarding apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Label switching type of packet forwarding apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Label switching type of packet forwarding apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3331182