Response: Cisco Closes Sourcefire Acquisition; Delivers Threat-Centric Security Model

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The announcement is a major change in Cisco Security strategy and perspective and, I think, a promising step forward: From a strategic standpoint, we will focus on a “threat-centric” security model moving forward – meaning that we will put a heavier focus on the threats themselves versus policy or controls. Given the fast-changing threat landscape, […]

Planning for Cisco Live 2013 in Orlando

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Cisco has sponsored the Packet Pushers Podcast to attend the Cisco Live 2013 event in Orlando, Florida. Although I will spend a lot of time in back rooms recording shows & receiving briefings ( always great to learn new things ) I have time set aside to meet people. Many listeners and readers have said that they would appreciate an opportunity to meet, say hello and have some discussions.

Rant: A Better Cisco Software Experience (Licensing) For Partners (but not Customers)

Cisco customers can update their licenses using this handy portal. Sounds good ? Exciting ? No, not the person who bought the software license, the partner that sold you the license can update the licenses. You might have forgotten who is Cisco’s real customer, and it’s not the person who paid for products. Partners, the […]

Sniffing on Cisco IOS on Unix (IOU) Emulator

Martin sent me an email about packet capture tool for IOU that he wrote. I haven’t tested it because I’m short on time right now so let me know what your experiences are: Some of you might already know IOU, it’s Cisco IOS compiled on Unix. It allows emulating routers and switches. One IOU process […]

◎ What’s Happening Inside an Ethernet Switch ? ( Or Network Switches for Virtualization People )

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I was going to call this article “Ethernet Switches for Virtualisation Engineers” but, really, everyone should have some understanding of the internals of an Ethernet switch. But particularly I want to focus on how multicast and broadcasts are handled in a high speed, low latency environment like a Data Centre Network.

It’s vital to understand that latency is critical to your application performance. It is common for a single transaction to take hundreds of round trips so a small increase in latency on each round trip has a large impact on the perceived performance. The client will send a chunk of data and wait for acknowledgement. Even setting up the TCP connection takes a few round trip – remember that TCP sessions are setup, and each data transfer is confirmed.

A modern network switch will have latency around 10 microseconds. The Cisco Nexus 7000 is about 8 microseconds & Brocade VDX 8770 claims less than 4 microseconds. There are many reasons why a switch can be faster or slower but I’ll look at a specific example

Remember, the latency interval is the time taken to receive a packet, decode the address, lookup the forwarding table, switch the packet (and copy it if needed) and transmit out of an Ethernet interface. That’s really fast processing. How does an Ethernet switch do this ?

The Huawei Security Problem Isn’t the Hardware, it’s Engineers Fixing the Bugs.

I’ve been thinking about the security issues of working with Huawei equipment and Huawei the company. I’ve spoken with a number of people who, off the record, talk of working with Huawei as customers and their experiences of the product have been less than excellent but the price is low. What I’ve realised is concerning. […]

Nexus 5500 Packet Forwarding – Cut Through or Store & Forward

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Was reading through some documentation as noticed that the Nexus 5500 series has some unusual behaviours for Store and Forward. I made myself notes about the functional modes. Cut-Through vs Store and Forward In cut-through mode of operation a switch will start transmitting a frame before the frame has been completely received and this is the […]