tag:blogger.com,1999:blog-16848720710778721642024-03-14T16:09:34.716+02:00Carrier Grade CommunicationsYaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comBlogger33125tag:blogger.com,1999:blog-1684872071077872164.post-90987397018379972992013-10-21T15:40:00.000+03:002013-10-22T11:43:25.035+03:00Geography (Installment 4 of a series)In the previous two installments of this series on SDN and NFV I
discussed the virtualization and configuration of communications
functionalities; this installment will deal with their placement. I call this
aspect geography, and this time use the term in its most literal sense – where
geographically a given function should be physically located.
Note that this aspect of a network function Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-60382030036472951452013-06-04T17:25:00.001+03:002013-06-05T17:57:17.055+03:00Philosophy (Installment 3 of a series)In the previous installments I
discussed the assimilation of communications and computation, the spectrum linking
hardware and software, and how to virtualize communications functionalities.
This installment is all about configurability and programmability.
I entitled this blog entry philosophy,
since philosophy is literally the "love of knowledge", and generally deals with
what we can learn Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-4997461675549472202013-04-29T14:00:00.000+03:002013-04-29T14:00:22.768+03:00Physics (Installment 2 of a series)In the previous installment of this series on NFV, SDN and related issues, I
talked about the relationship between communications and computation (the
merging of which I dubbed computications); now we are ready to take these ideas
one step further.
A computational resource (such as
a server or a laptop computer), as well as a communications resource (such as a router or a
switch), may be a Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-49247150316706146462013-04-25T18:00:00.000+03:002013-04-29T09:32:53.373+03:00Computications (Installment 1 of a series)We have been hearing a lot recently about Network Functions Virtualization
(NFV), Software Defined Networking (SDN), and how communications could learn a
lot from computer science. This is the first blog entry of a series in which I
will attempt to impose some structure on these ideas by exploring five distinguishable
trends, which I shall dub, respectively :
Computications (on the relationshipYaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-63598625689659644082013-01-09T19:13:00.001+02:002013-01-09T19:13:57.719+02:00CAPping routed and SDN networksIn my last blog entry I discussed two differences between SDN and conventional networking. The second was that SDN returns to centralized control as compared to a distributed control plane (I’ll return to the first difference in just a moment). And this means that there is a single point of failure, even if the controller itself has built-in redundancy.
There has been discussion in the OpenFlow Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-90822433868498014932012-10-09T19:39:00.000+02:002012-10-09T22:56:53.981+02:00SDN : A Backward Step ForwardEveryone in the industry is talking about Software Defined Networks or SDNs, but unfortunately no two people using the term mean precisely the same thing. However, after hearing dozens of academicians and even more networking converts, and after reading hundreds of press releases, I believe that when people mention SDN they are talking about a network based on one or both of two guiding Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-89496792739178650682012-08-19T18:22:00.000+03:002012-08-20T09:44:59.463+03:00Quality of Experience (QoE)As a reader of this blog you are doubtless familiar with the concept of the Quality of Service (QoS) of a telecommunications service, by which we mean meeting defined levels of a set of measureable network parameters, such as availability, delay, delay variability, and information loss. The precise set of parameters depends on the service type; for example Bit Error Rate (BER) and Errored SecondsYaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-44209752644486570582012-05-20T09:47:00.002+03:002012-05-20T09:47:39.932+03:00What is time ?There is an anecdote about a foreigner visiting London asking a man on the street “what is time?” and receiving the answer “I’m sorry, but I am not a philosopher”.
I don’t want to discuss here the philosophical or physical questions of what time is, but rather what we mean by time in telecommunications applications. In particular, we frequently hear the terms “UTC”, “GPS time”, “NTP time”, and “Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-35424910424866095002012-05-08T18:36:00.001+03:002012-05-08T18:37:38.224+03:00iPhone StormsA few years ago RAD’s president Zohar Zisapel asked me to accompany him to a meeting with another Israeli company concerning possible cooperation on an important issue. On our way I asked him what this important issue was. He replied the iPhone problem and I immediately understood.
He informed me that he had been in the US the previous week, and although he carried a Blackberry and not an Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.comtag:blogger.com,1999:blog-1684872071077872164.post-90851663187672318312012-01-09T16:42:00.000+02:002012-01-09T16:42:28.784+02:00Jobs and RitchieOctober 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+02:002012-05-08T18:38:57.763+03:00The meaning of Apple's '647 patentOn 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+02:00On exa, zetta, and beyondAnyone 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+02:00My new CTO jobAs 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+02:00MPLS-TP updateAt 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+02:00The notorious IP checksum algorithmI 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+02:00Network CodingIn 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.InYaakov (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+03:00The PW Associated ChannelIn 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"Seamless MPLS" and Denial of ServiceA 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+02:00MPLS is not a "successful" protocolRFC 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+02:00Reliable transport vs. reliable transportOne 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 assumedYaakov (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+02:00IETF79 - Beijing !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+02:00OAM for flowsContinuing 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+02:00IETF and OAMOn 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, whenYaakov (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+02:00OAM for FM and PMThe 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+03:00Deployment, R&D, and protocolsIn 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&Yaakov (J) Steinhttp://www.blogger.com/profile/17092448930584936036noreply@blogger.com