5 Replies Latest reply on Jun 24, 2011 1:15 AM by content.librarian

# Random Transaction Rate: The new high speed memory performance metric

In the networking world, routers and switches deal with a sequence of random packets that need to be routed/switched to destinations dictated by their header fields after appropriate security checks and classification. Each packet requires 15-25 memory transactions to random locations before it is routed from the ingress to an egress of the router/switch.

Random transactions Rate are the # of fully random memory accesses (reads or writes) that can be performed on the memory. Simply stated it is the rate at which random data can be addressed (or random address rate).This metric is independent of the number of bits being accessed for the transaction (transaction bit width). Random transactions rate would be measured in million transactions per second or MT/s.

Memory Random Transaction Rate (RTR) is currently one of the major limiting factors for the continued increase in networking line and switching rates.
• ###### 1. Re: Random Transaction Rate: The new high speed memory performance metric

Hi Jayasree,

Could you advise a example for the RTR?  Like 100GE, the packet buffer, what is the RTR needed?

Besides, is RTR the stander metrix for SRAM performance?

Thanks

Haiping

• ###### 2. Re: Random Transaction Rate: The new high speed memory performance metric

For a 100GE interface, the packet rate (R) would be 150MP/s.

For a Packet buffer application,the random transaction rate range is (4R-6R) MT/s where R is the Packet rate. This comes upto 600-900MT/s

• ###### 3. Re: Random Transaction Rate: The new high speed memory performance metric

Why do you need to multiply the Packet Rate by 4 or 6 ? where does this come from?

• ###### 4. Re: Random Transaction Rate: The new high speed memory performance metric

The Random Transaction Rate = Packet Rate (R) x (# of Accesses/packet)

The # of Accesses/packet for Packet Buffer application ranges between 4 and 6.Hence the Packet Rate (R) is multiplied by this factor.

• ###### 5. Re: Random Transaction Rate: The new high speed memory performance metric

Ok

that may be true for the packet buffer function. But what about statistics? Look up tables, scheduling?

Are there others?

• ###### 6. Re: Random Transaction Rate: The new high speed memory performance metric

Below are the RTR for the following applications.

Statitics : 2R MT/s

Lookup tables :4R-8R MT/s

Scheduling :: 2R MT/s