tag:blogger.com,1999:blog-16848720710778721642012-01-09T16:46:03.999+02:00Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comBlogger241100tag:blogger.com,1999:blog-1684872071077872164.post-90851663187672318312012-01-09T16:42:00.000+02:002012-01-09T16:42:28.784+02:00

October 2011 marked the passing away of two men well-known in the computation and communications industries. One was Steve Jobs. In his honor Apple, Microsoft, and Disneyland all flew their flags at half-staff. October 16, 2011, was declared "Steve Jobs Day" in California. President Obama gave a eulogy calling Jobs “among the greatest of American innovators … a visionary”. The other was Dennis

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-34086292507063263182011-12-25T14:50:00.015+02:002011-12-25T18:05:47.241+02:00

On December 19th the U.S. International Trade Commission (ITC) issued its final determination on Apple's claims against HTC of Taiwan, finding that HTC violated Section 337 of the Tariff Act by selling Android phones containing a technology that infringed a patent held by Apple. Section 337 enables the ITC to block importation into the US of foreign products that unfairly compete with domestic

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-53391217719382569672011-11-30T11:10:00.008+02:002011-11-30T14:57:25.035+02:00

Anyone who lives in metric system countries knows what "kilo" means. A kilogram is 1000 grams, a kilometer is 1000 meters. Of course frequencies are measured in kiloHertz and in the computer world we have kilobits and kilobytes (although we are never quite sure if that is 1000 or 1024!).Most people even know that "mega" means a million. Power stations output megawatts of electricity, FM radios

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-25333197920127075292011-11-23T19:12:00.004+02:002011-11-23T19:38:40.716+02:00

As you all probably know, I have changed job titles.I am now RAD's Chief Technology Officer instead of (or perhaps in addition to?) Chief Scientist.Our previous CTO, Prof. Daniel Kofman, is still in touch with the company. However, he is a bit busy since in addition to his position as Professor at Telecom ParisTech (formerly ENST), he has been appointed by France's Minister of Research and

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-57216916114876729212011-11-17T16:29:00.006+02:002011-11-17T16:46:05.918+02:00

At the MPLS Working Group meeting this week it was announced that the core set of MPLS-TP RFCs have been finished.Indeed, we now have (I hope that I haven't missed too many):•RFC 5586 MPLS Generic Associated Channel (G-ACh and GAL)•RFC 5654 Requirements of an MPLS Transport Profile•RFC 5718 An In-Band Data Communication Network for MPLS-TP•RFC 5860 Requirements for OAM in MPLS Transport Networks•

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-81947638737738891732011-11-16T19:12:00.008+02:002011-11-16T19:34:11.956+02:00

I have been asked several times to explain the checksum calculation used in the IP suite (IPv4, TCP and UDP all utilize the same checksum algorithm).RFC 791, which defines IPv4, gives the checksum algorithm as follows :The checksum field is the 16 bit one's complement of the one'scomplement sum of all 16 bit words in the header. For purposes ofcomputing the checksum, the value of the checksum

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-60764045969187869872011-10-05T19:53:00.013+02:002011-10-06T07:07:12.057+02:00

In conventional communications networks the active network elements (e.g., Ethernet switches or IP routers) are store-and-forward devices. They perform no nontrivial computation. It turns out that in certain cases it is possible to optimize network operation (to conserve some network resource or to improve some network performance measure) by embedding more intelligence in the network elements.In

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-45751621886983314602011-08-21T11:50:00.014+03:002011-08-21T14:00:24.300+03:00

In the beginning of the development of pseudowire technology, it was obvious to many of us that PWs would require some sort of OAM support. As always with OAM the question was how to make OAM packets fate-share with user data packets. The original RAD proposition was to define a special "OAM PW" that would be placed alongside the monitored PWs. In the MPLS case this meant a special PW label for

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-84207339184954049982011-05-30T16:02:00.010+03:002011-05-30T16:38:13.787+03:00

A Denial of Service (DoS) attack is an attack that attempts to render a service temporarily unavailable to legitimate users of the service. DoS attacks are carried out by attackers disrupting the function of any link in the service supply chain. In the context of services provided over telecommunications networks, DoS attacks can be directed at a web or mail server, routers, or at any necessary

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-22895440991059976162011-01-10T09:51:00.004+02:002011-01-10T10:08:24.042+02:00

RFC 5218 defines what the Internet Architecture Board considers to be a "successful" protocol. A "successful" protocol is one that meets its original goals and is widely deployed, such as DNS, BGP, SMTP, and SIP. A "wildly successful" protocol far exceeds its original goals in terms of purpose and scale. Examples of the latter are IPv4, ARP, and HTTP. A protocol may be considered successful even

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-19025770895481469742010-11-29T13:46:00.004+02:002010-11-29T14:29:53.170+02:00

One of the most contradictory uses of terminology in communications concerns the word transport as used by the IETF and the ITU-T communities. To make matters worse, the term’s prevalent modifier reliable leads to even further divergence in meaning.To the Internet community, transport refers to the fourth layer of the OSI layer stack (a layer stack known to the ITU-T as X.200, but largely assumed

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-74351765699672201322010-11-23T23:05:00.002+02:002010-11-23T23:15:24.027+02:00

I haven’t had much time to blog of late, having to catch up on work since returning from Beijing.Beijing ? I hear you ask. Yes, the 79th IETF meeting was held 7-12 November in the Chinese capital.This was my 26’th IETF, and things have changed since my first meeting. Back in the “old days” the meetings were mostly in the US (e.g., Minneapolis in the winter) and occasionally in Europe. This was

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-75236129054065731922010-11-02T21:47:00.003+02:002010-11-02T21:54:10.344+02:00

Continuing my coverage of the recent joint IESG/IAB design team on OAM, this time I want to discuss the issue of OAM for flows in Packet Switched Networks (PSNs).From a pure topology standpoint any communications network is imply a set of source ports (i.e., interfaces into which we may input information), a set of destination ports (i.e., interfaces from which we may receive information), and a

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-16192761251866836942010-10-28T14:38:00.005+02:002010-10-28T15:03:14.547+02:00

On October 12nd and 13th the IESG (Internet Engineering Steering Group) and IAB (Internet Architecture Board), the two IETF management bodies, held a joint design session on OAM. I was a bit surprised that the IETF leadership would be interested in devoting a separate meeting (not coinciding with an IETF conference) to the subject of OAM; OAM has never been an area of IETF expertise. Indeed, when

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-21502974225349158292010-09-29T12:04:00.006+02:002010-09-29T12:21:17.901+02:00

The Operations, Administration, and Maintenance (OAM) functionality provided in all modern communications systems supports two distinguishable functions, namely Fault Management (FM) and Performance Management (PM).It is important to remember that despite the use of the word “management” here, OAM is a user-plane function. OAM may trigger control plane procedures (e.g., protection switching) or

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-18326313387623341882010-09-08T12:56:00.003+03:002010-09-08T13:00:58.650+03:00

In my last entry I discussed why the last mile is a bandwidth bottleneck while the backhaul network is a utilization bottleneck. Since I was discussing the access network I did not delve into the core, but it is clear that the core is where the rates are highest, and where the traffic is the most diverse in nature.Based on these facts, we can enumerate the critical issues for deployment and R&D

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-34989939526117016322010-08-26T12:04:00.004+03:002010-08-26T12:17:38.264+03:00

Let us consider an end-to-end data transport path that can be decomposed into the following segments* end-to-end path = LAN + access network + core network + access network + LANThere may be distinct service providers for each of these segments, thus many different decompositions may make sense from the business perspective. Yet, the identity of the access network, and of its components * access

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-61946611701740244092010-08-19T14:16:00.003+03:002010-08-26T12:18:45.807+03:00

My last entry provoked several emails on the subject of the terms last/first mile vs. access networks. While answering these emails I found it useful to bring in an additional term – the backhaul network. Since these discussions took place elsewhere, I thought it would be best to summarize my explanation here.Everyone knows what a LAN is and what a core network is. Simply put, the access network

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-43747150360045523562010-08-08T14:37:00.003+03:002010-08-08T14:43:21.570+03:00

Physical-layer access technologies with limited range are usually called last mile technologies. More specifically, we usually use the expression last mile when considering xDSL, that enables several Mbps to be transported over several kilometers, or a fiber optic link or PON, that enable hundreds or even thousands of Mbps to be transported over tens of kilometers.In the year 2000 the IEEE

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-69237590194348491382010-08-02T14:42:00.000+03:002010-08-02T15:22:41.901+03:00

IP addresses (even 4-byte IPv4 ones), are generally not easy to remember, which is why humans prefer to type domain names into their browser address window, even if they are longer. It is job of the Domain Name System (DNS) to translate the domain name into the correct IP address, which is placed in the IP header and enables proper forwarding.The DNS works recursively in the following way. When

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-56045352839608880772010-07-29T00:25:00.000+03:002010-07-29T00:35:48.421+03:00

This entry is an update for people who have been following the IETF TICTOC working group that I chair. We had a very lively meeting yesterday, and the topic that evoked the most interest was that of how to transfer timing flows (especially 1588, but NTP as well) over MPLS networks.The first question is why anything special treatment is needed here at all - after all, anything that can be carried

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-15401105554134618472010-07-28T13:21:00.000+03:002010-07-29T00:38:02.252+03:00

I am in Maastricht at the 78th IETF meeting.In the weeks before the meeting many IETF'ers complained about the fact that there were no direct flights to the venue. The closest airports are Amsterdam and Brussels, but from there three trains had to be taken.At first I had thought that the problem was related to carrying luggage between trains, but discovered that the concerns were more about the

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-58640295290666614412010-07-26T19:06:00.001+03:002010-07-26T19:46:20.878+03:00

My wife and I cultivate succulents, plants that store water. Cacti are succulents, but we don’t collect them – only the cuddly and outwardly types. What I find so interesting about succulents is that the various types are relatively unrelated – there was never a proto-succulent that evolved into many subspecies. Instead many different kinds of plants developed similar mechanisms to cope with the

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-67100769534246198732010-07-21T11:05:00.000+03:002010-07-26T19:50:58.310+03:00

This is my first blog entry on the world of traffic shaping. We have all been hearing about the need for shaping in 3G mobile networks. The subject’s popularity exploded with the publicity of network overload problems that some operators were experiencing with the introduction of the iPhone. Most of that turned out to be due to signaling overload. However, almost everyone is convinced that if

Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.com