Method for data transfer through a bridge to a network requiring source route information

• US 4,947,390 A
• Filed: 03/22/1989
• Issued: 08/07/1990
• Est. Priority Date: 03/22/1989
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Sheehy, David B.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Jung, Min
• Application Number:
  US07/327,202
• Time in Patent Office: 503 Days
• Field of Search: 370/85.13, 370/85.14, 370/94.1, 370/85.12, 340/825.5, 340/825.51
• US Class Current: 370/401
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof

Abstract

A method for handling data frames (71,81) by a bridge (51) between a first network (61) which does not require route information within data frames (71,81) and a second network (21,22,23,24,25) requiring route information (74) within data frames (71,81) is presented. A system memory (12) includes an address table (14,140,141). In the address table (14,140,141) are a plurality of entries. Each entry is for a single station (31-60) on the first network (61) or the second network (21,22,23,24,25). Each entry contains a first field (17,170,171) which is the address of the station (31-60) and when the station (31-60) is in the second network (21,22,23,24,25) the entry additionally includes a second field (19,191) which contains a route to the station (31-60). When a first data frame (81) having a first destination address (72) is received from the first network (61), the address table (14,140,141) is checked for an entry which has the first destination address (81) in the first field (17,170,171). If an entry is found indicating that the first destination address (81) is for a station (31-54) in the second network (21,22,23,24,25), the route information (74) in the second field (19,191) is added to the first data frame (81) to create a first modified data frame and the first modified data frame is sent out on the second network (21,22,23,24,25). If no entry is found for the first destination address (81) a route discovery process is initiated to discover a route to the station (31-54) on the second network (21,22,23,24,25) with the first destination address (81).

Claims

1. A method for handling data frames (71,81) by a bridge (51) between a first network (61) which does not require route information within data frames (81) and a second network (21,22,23,24,25) requiring route information (74) within data frames (71), the method comprising the steps of:

(a) receiving a first data frame (81) from the first network (61), the first data frame (81) having a first destination address (72);

(b) when the first destination address (72) addresses a station (31-54) on the second network (21,22,23,24,25) and the bridge (51) has route information (74) to the station (31-54) on the second network (21,22,23,24,25), performing the following substeps;

(b1) adding first route information (74) to the first data frame (81) to create a first modified data frame, and

(b2) sending the first modified data frame out on the second network (21,22,23,24,25); and

,

(c) when the first destination address (72) addresses a station (31-54) on the second network (21,22,23,24,25) and the bridge (51) does not have route information (74) to the station (31-54) on the second network (21,22,23,24,25), initiating a route discovery process to discover a route to the station (31-54) on the second network (21,22,23,24,25).

2. A method as in claim 1 additionally comprising the step of:

(d) maintaining an address table (14,140,141) which includes the addresses for stations (51,55-60) on the first network (61) and which includes addresses and route information (74) of stations (31-54) on the second network (21,22,23,24,25) for which stations (31-54) on the second network (21,22,23,24,25) for which route information (74) is known by the bridge (51).

3. A method as in claim 2 additionally comprising the step of:

(e) receiving a second data frame (71) from the second network (21,22,23,24,25), the second data frame (71) having a second destination address (72) and a source address (73); and

,

(f) when the bridge (51) is referenced in the second route information (74), performing the following substeps;

(f1) removing route information (74) from the second data frame (71) to create a second modified data frame, and

(f2) sending the second modified data frame out on the first network (61), and

(f3) when the source address (73) is not in the address table (14,140,141) creating an entry in the address table (14,140,141) which includes the source address (73) and route information (74) derived from the route information (74) in the second data frame (71).

4. A method as in claim 2 additionally comprising:

(e) maintaining an address cache (11) in which is stored an address for every entry in the address table (14,140,141).

5. A method as in claim 1 wherein step (c) additionally includes discarding the first data frame (81) when the first destination address (72) addresses a station (31-54) on the second network (21,22,23,24,25) and the bridge (51) does not have route information (74) to the station (31-54) on the second network (21,22,23,24,25).

6. A bridge (51) between a first network (61) which does not require route information within data frames (71,81) and a second network (21,22,23,24,25) requiring route information (74) within data frames (71,81), the bridge (51) comprising:

a first memory (3) which receives data frames (71,81) from the first network (61) and from the second network (21,22,23,24,25), the data frames (71,81) each having a destination address (72,82);

a system processor (9), coupled to the first memory (3), the system processor (9) monitoring data frames (71,81) received by the first memory (3); and

,

a system memory (12), coupled to the system processor (9), the system memory (12) including an address table (14,140,141), the address table (14,140,141) including a plurality of entries, each entry being for a single station (31-60) and each entry including a first field (17,170,171) containing an address of the station (31-60), and when the station (31-60) is in the second network (21,22,23,24,25) the entry includes a second field (19,191) which contains a route to the station (31-60);

wherein when the first memory (3) receives from the first network (61) a first data frame (81) having a first destination address (72), the system processor (9) searches the address table (14,140,141) for the first destination address (72),

the system processor (9) adding first route information (74) to the first data frame (81) to form a first modified data frame and sending the first modified data frame out on the second network (21,22,23,24,25) when the system processor (9) finds a second entry in the address table (14,140,141), the second entry including the first destination address (72) in a first field (17,170,171) of the second entry, and the first destination address (72) being address of a station (31-54) on the second network (21,22,23,24,25), and

the system processor (9) initiating a route discovery process to a station (31-54) on the second network (21,22,23,24,25) with the first destination address (72) when no entry in the address table (14,140,141) contains the first destination address (72).

7. A bridge (51) as in claim 6 wherein when the first memory (3) receives from the second network (21,22,23,24,25) a second data frame (71) having second route information (74) and a source address (73), the system processor (9) searches the second route information to determine whether the bridge (51) is in the second route information (74),

the system processor (9) removing the second route information (74) from the second data frame (71) to form a second modified data frame and sending the second modified data frame out on the first network (61) when the system processor (9) determines the bridge (51) is referenced in the second route information (74), and

the system processor (9) adding a third entry to the address table (14,140,141), the third entry having the source address in a first field (17,170,171) address, and a second field (19,191) having route information (74) derived from the second route information (74) when the second destination address (72) is the address of a station (51,55-60) on the first network (61) and no entry in the address table (14,140,141) contains the the source address.

8. A bridge (51) as in claim 6 additionally comprising an address cache (11), coupled to the system processor (9), the address cache (11) containing at least a portion of addresses contained in the first field (17,170,171) of entries in the address table (14,140,141).

9. A bridge (51) as in claim 6 wherein the system processor (9) discards the first data frame (81) when the system processor (9) finds a first entry in the address table (14,140,141) which includes the first destination address (72), the first destination address (72) being the address of a station (51,55-60) on the first network (61).

10. A bridge (51) as in claim 6, each entry in the address table (14,140,141) including a third field (18) indicating in which of the first network (61) and the second network (21,22,23,24,25) a station (31-60) listed in the first field (17,170,171) of the entry resides.

11. A bridge (51) as in claim 6 wherein when the first memory (3) receives from the second network (21,22,23,24,25) a second data frame (71) having second route information (74), a second destination address (72) and a source address (73), the system processor (9) searches the second route information (74) to determine whether the second data frame (71) is an explorer message of the all routes type and searches the address table (14,140,141) to determine on which network (21,22,23,24,25,61) a station (31-60) with the second destination address (72) resides, the system processor (9) discarding the second data frame (71) when both the second data frame (71) is an explorer message of the all routes type and the second destination address (72) addresses a station (31-54) on the second network (61).

12. A method for handling data frames (71,81) by a bridge (51) between a first network (61) which does not require route information within data frames (71,81) and a second network (21,22,23,24,25) requiring route information (74) within data frames (71,81), the method comprising the steps of:

(a) receiving a first data frame (81) from the first network (61), the first data frame (81) having a first destination address (72);

(b) when the first destination address (72) addresses a station (31-54) on the second network (21,22,23,24,25) and the bridge (51) has route information (74) to the station (31-54) on the second network (21,22,23,24,25), performing the following substeps;

(b1) adding route information (74) to the first data frame (81) to create a first modified data frame, and

(b2) sending the first modified data frame out on the second network (21,22,23,24,25); and

,

(c) when the first destination address (72) addresses a station (31-54) on the second network (21,22,23,24,25) and the bridge (51) does not have route information (74) to the station (31-54) on the second network (21,22,23,24,25), initiating a route discovery process to discover a route to the station (31-54) on the second network (21,22,23,24,25).

13. A method as in claim 12 additionally comprising the steps of:

(d) receiving a second data frame (71) from the second network (21,22,23,24,25), the second data frame (71) having second routing information (74) and a source address (73);

(e) when the bridge (51) is in the second route information (74), performing the following substeps;

(e1) removing the second route information (74) from the second data frame (71) to create a second modified data frame, and

(e2) sending the second modified data frame out on the first network (61), and

(e3) when the source address (73) is not in the address table (14,140,141) recording in a memory the route information (74) derived from the second route information (74) in the second data frame (71).