3Com 7600 User Manual

3

Com

7600 Fast Ethernet Interface Card

RELEASE NOTES

Software Release 3.50

( Revision control - Version 1.0 - Published version )

About this SW version 3.50

The 7600 software version 3.50 is intended for use with the CoreBuilder 7000 (REV. C) and CoreBuilder
7000HD ( all revisions ) switch board .

This version includes new features/functionality enhancements as well as bug fixes for technical problems
found in the latest release of the 7600 card , version 3.31.

It is strongly recommend to use the CoreBuilder 7000/7000HD software version 3.50. Using this version
will provide the best level of feature support and more recent bug fixes.

The official released version of 3.50 can be identified precisely by checking the LMA menu sequence :
System/Display for compilation date of 12/10/97 at 16:23:25. The time stamp of the files themselves is

12/10/97 at 17:19 .

New Features in S/W Ver. 3.50

The following new features have been added in Software Release 3.50 :

LAN Emulation

• Frame Buffering During Move from BUS to Data Direct.

When a LEC begins transmitting data to a new destination MAC address, it first sends an LE_ARP to
the LES, and simultaneously then begins broadcasting data frames through the BUS. This continues
until a Data Direct is either found or set up between the source LEC and the destination LEC . At this
point, the source LEC would like to start transmitting through the (much faster) data direct VCC.
However, it must wait until all data sent via the BUS arrives at its destination. The LANE standard
defines a flush request frame which the source LEC sends to the BUS. This frame indicates to the
LANE process that no more frames should be sent via the BUS, and that all further frames are to be sent
via the data direct after the source LEC receives the Flush Response from the destined LEC if the time­out for the Flush Response has been expired.

The standard defines that the destined LEC, after receiving the flush request frame and ensuring that all
frames have been sent to the destination MAC address sends a flush response frame confirmation to the
source LEC. The source LEC only begins transmission via the Data Direct path after it has received the
flush response through the Control Direct confirmation to the flush request, or a time-out has expired.

The LANE standard does not define what is done with the data that arrives at the source LEC during the
time between the LEC sends the flush request frame to the BUS, and the time it receives the flush
response. The time required to receive the flush response is normally on the order of tens of
milliseconds. The enhancement implemented in this version, stores the data arriving during the flush
period in a temporary buffer and therefore enables more reliable operation of connectionless protocols
such as TFTP and NFS that utilize UDP. It is important to note that the described phenomena with the
data received during the flush period is related to the required time interval to set-up the Data Direct
VCC.

2

The number of frames buffered can be set to a value between 1 and 4. (The default number is 2). When
the flush response received by the source LEC , the 7X00 first sends the frames stored in its buffers over
the Data Direct VCC, and only then begins normal transmission of data on the data direct.

The solution buffers frames for an operator-definable number of destination MAC addresses. This
number can be set to between 1 and 3. The default number of MAC addresses is 3.

The frame buffer during flush solution can be managed via the Local Management Application (LMA)
in admin mode. The menu le\Buffer (see below) allows the operator to display the buffer status, enable
or disable (the default value) the buffer operation and set the number of frames buffered and number of
destination MAC addresses to be handled.

7400 Card in slot #4 context #0 - flush menu:
=============================================
[1] display - Display MAC buffer status
[2] enable - Toggle Enable/Disable MAC buffer
[3] frames - Set number of frames per MAC in buffer
[4] entries - Set number of entries (MAC addresses) in MAC buffer

• A mapping between MAC addresses to the VPI/VCI, through which the MAC addresses have been

appeared from the ATM side, may be displayed through the LMA in the bridge Forwarding Data Base
(FDB) table( Bridge/FDB/Display or Learned menu ).

• Terminate LEC and its all Data-Direct connections to the ATM side may be performed through the

LMA ( LE/Terminate menu ).

• Terminate MID - termination of all VCCs to a specific ATM address may be performed through the

LMA( LE/MID/Terminate menu ).

Performance Improvement

• The new version 3.50 of the 7600 interface card implements a new concept for the frame flow handling.

This new concept increases the 7600 performance. This enhancement increases the system throughput
in forwarding cells through the ATM side towards the switch engine. The two main aspects are:

∗ Full line rate for any single session running between the Fast Ethernet ports.
∗ The total aggregated bandwidth per 4 ports is up to 310 Mbps all the way from the

Arbiter through the ZipChip toward the backplane and the switch engine and all the
way back as well.

• In order to take advantage of this performance improvement, select option number two (50Mhz) in the

System/Update/Frequency LMA menu. A reset is required in order to validate this modification as
indicated by the LMA monitor prompt.

Notes:

⇒ It is highly recommend to use this option (50Mhz), otherwise by using the default option (33Mhz)

the performance for frame length less then 128 bytes will be less then the full rate.

⇒ Short mode ( only the lower 8 ports are functioning) is not available in the current version .

3

Miscellaneous

• LMA Timeout:

The CoreBuilder 7000 Local Management Interface (LMA) allows users to access the LMA of each
interface card (7200/7400/7436/7600) directly, without the need to connect to the interface cards
directly. This is true for both a direct console terminal connection and via Telnet. Moreover, when a
user moves from a module menu to the switch menu (or to another module menu) the LMA maintains
the session to the intelligent interface module, thus preserving the menu location for future access.
Since only a single user can use the intelligent module’s LMA at any one time, a user may make this
interface inaccessible to other users, whether they attempt to use it from the system console or via
Telnet. If the access to the switch is via Telnet, the only way to access the module’s LMA may be to
resetting it.
Solution: The LMA (RS232 or Telnet) is disconnected (Telnet) / logged out (RS232) when a specific
timeout (with no user activity) has expired, after which other LMAs (new or existing) sessions can be
established as they would if this LMA has disconnected/logged out manually. The hard coded value for
the timeout is 15 minutes.

7600 Card SW Bug Fixes In Version 3.50

The following bugs have been fixed in Software Release 3.50 :

• Port administration status : “Disable” does not save properly in the Flash memory , therefore after a reset

the actual port administration status returns to be “Operational” . In order to disable again the port
administration status the user must first Enable the port status and then Disables it again.

• The redundant switch engine capability is not supported in a CoreBuilder 7000 which is populated by

7600 and/or 7400 modules only. The CoreBuilder 7000 should house at least one 4-ATM port module,
7200 module or 8-ATM port card in order to support redundant switch capability. There is no restriction
on the slot number that the interface modules must be placed in, when using the CoreBuilder 7000
version 3.20-Fixed in conjunction with version 3.50 of the CB7000.

• The NMS’s LANsentry application , which its MIB is a part of the RMON standard MIB , fails to “get”

RMON information. For more details refer to 7600 Software Clarifications and Restrictions section.

• When “NotFlood” method, which is blocking the actual data flow through the BUS during the LAN

Emulation Data-Direct VCC creation process, is enabled for a specific bridge, then the bridge entity can
not be managed by SNMP protocol even does not answer to pings which are destined to its management
agent IP address.

• Spanning Tree LANE Topology Requests - With Spanning Tree Protocol enabled, too many LE

topology requests were being sent. As a result , the system software was required to process the huge
number of requests, thereby lowering software performance. This can potentially affect the speed of the
LMA display, address learning or even connections to interface cards (e.g. -"Error in connection to
module" message) but does not affect forwarding performance (which is performed in hardware).

• When STP is enabled, after bridge initialization or VN dynamic change, ports are passing too fast from

Blocking state into Forwarding state, so BPDU frames not to be received by these ports causing them to
move directly to the Forwarding state. Therefore, a short broadcast storm may be occurred till the ports
which have been moved rapidly from Blocking to Forwarding state will receive the BPDU frames and
as a result they will be moved back to the Blocking state. From this stage the entire tree structure will be
built correctly and the ports will be set in their final and appropriate states (Blocking or Forwarding).

4