Summer schedule
I’m switching to the “traditional” summer schedule: until mid-August, I’ll post two to three shorter articles per week. I don’t want to spend too much of my vacation time writing, but I also don’t want to see you bored with dormant blogosphere.
Some of my projects will simply have to wait for the temperatures to drop, including a few selected Service Provider issues I’ve started writing about in the last weeks and the ADSL QoS topics (don’t worry, I haven’t forgotten them).
Wimax: the next disruptive technology?
Fifteen years ago, the focus of the “true” service provider was on voice traffic and data offerings based on virtual circuits, implemented with a plethora of semi-compatible technologies slowly developed within the ITU organization: X.25, ISDN, Frame Relay and the all-encompassing ATM.
In the meantime, some relatively small companies (including Cisco, Wellfleet and 3Com) were producing so-called “routers” that supported two technologies nobody took seriously: Ethernet and IP.
Cisco IOS Hints available on Kindle
Followup: VLAN interface status
Thanks to my readers, I often learn something completely new about the intricacies of Cisco IOS. The “VLAN Interface Status” post resulted in a comment about the SVI autostate concept, which is (not surprisingly) a somewhat muddy topic:
- In most cases, the SVI interface tracks the state of access and trunk ports using the VLAN. The details are well explained in the Understanding SVI Autostate section of the Cisco IOS documentation.
The important part of the SVI autostate calculation is the “port is in STP forwarding state for the VLAN” requirement. If a VLAN is not carried in a trunk port (for example, due to switchport trunk allowed configuration command), the trunk port’s status does not influence the autostate.
PE-to-PE IPSec: do you have creative ideas?
Ying would like to have a PE-to-PE IPSec protection for traffic within a single VRF. For example, all traffic in VRF-A sent between PE-1 and PE-2 should be protected with IPSec and the PE-routers should be the endpoints of the IPSec session (CE-to-CE IPSec is trivial).
My first response was “hard to do”, then I started hallucinating about MPLS-over-GRE-over-IPSec-over-IP-over-MPLS tunnels between the PE-routers with tunnel-specific IGP and per-VRF BGP next hops. It can be done (we’ve implemented numerous large-scale MPLS/GRE/IPSec designs), but is there a simpler alternative? Please share your ideas in the comments.
Quick tip: VLAN interface status
Vijay sent me this question a while ago:
I have configured a L3 VLAN interface on a Cisco 3750 switch and assigned an IP address to it. I haven't assigned any ports to this VLAN. Why am I not able to ping the IP address of the VLAN interface from the switch itself?
The VLAN interface (like any other interface) has layer-1 and layer-2 state.
Question everything
In one of our discussions, Stretch provided an excellent graph illustrating that the ISP competition seems to reduce prices almost linearly and asked me in a later comment to justify the inverse relation between subscription charges and consumer choice.
You might consider this debate to be purely between Stretch and myself, but it’s an interesting example of what you might need to do in daily your job. If you want to be a great networking engineer, you have to be prepared to question everything, including common wisdoms, “well-known truths”, “common practices” and facts that look too good to be true. Ready? Let’s go …
Looking for additional information on Netflix video streaming
I'm looking for details on how Netflix streams videos over the Internet. I've found their description of encoding and bit rates, but was not able to find lower-layer details (I can only assume they use UDP, but I would like to verify that with someone who's actually using the service).
I would also appreciate any information on whether they work with Service Providers (for example, using local direct peering) to ensure the upstream Internet connections are not clogged with streamed video.
Drawing the diagrams
Every so often, someone asks me what tools I use to draw the diagrams. Years ago I was perfectly happy with Visio, but since Microsoft bought it, it became so bloated that I’ve been forced to drop it (it would take minutes to start on my laptop) and revert back to PowerPoint.
Followup: All-I-can-eat
The “All-I-can-eat-mentality” article has triggered (as expected) numerous responses. Some of them provided useful data, links to more information or informative perspectives – many thanks to those readers. A few others were unfortunately following the “I-am-right” line without considering facts. Most of the readers from the Service Provider community decided to stay anonymous (when you read all the comments, it becomes obvious they made a wise decision) or respond off-line.
Whatever your position in this issue, I would like to ask you to keep your comments focused on the topic. Although you were all infinitely more polite than the usual forum/blog crowd and provided some really good arguments, writing angry replies does not help. What’s happening with Internet is (like it or not) our common problem … or you could take the blue pill and continue bashing the other side.
I particularly liked the summary of our discussion posted on Slashdot (where someone included the link to my blog):
Whoa, whoa, whoa, that article seems to be promoting a balanced viewpoint that denies a) that telcos are totally evil and b) that we should all be allowed to have as much bandwidth as we want and not have to pay for it. We'll have none of that nonsense on /.