One of the reasons that traditional land-line telephone service is going the way of the dinosaur is cell phones. The other is Voice (or Video) Over Internet Protocol. The advantages of VOIP are obvious - let's say you're in the US and you want to talk to somebody in the UK. Traditional phone service will absolutely kill you for that privilege. VOIP will be free. Other advantages include webcam integration (video phones, in other words) and the ability to more carefully and granularly manage a site's voice and data network.
VOIP can go over traditional analog phone sets via an adapter (in this case, a VOIP router, PBX or even a workstation with an Analog Telephone Adapter) over specialized IP telephones, or over a workstation with a softphone program (like Skype or Ventrillo) installed on it and a headset plugged in.
VOIP can also mean Video Over Internet protocol and in this case encompasses things like the aforementioned videophone, but also live camera feeds (a lot of modern security systems use this) or streaming video from a server (such as youtube).
Behind the scenes VOIP uses a protocol called SIP (Session Initiation Protocol) to regulate the packets and make sure the incoming data is formatted in a manner the player it's going to can make sense of.
This one is near and dear to me - I use Skype to stay in touch with some friends who are out of state, and I watch online TV on hulu and movies via Netflix.
Monday, November 30, 2009
Chapter 10: TCP/IP Arcana (In depth TCP/IP)
This chapter covered three primary topics: subnetting, mail services, and TCP/IP utilities.
Subnetting is the process by were a single IP address can be split into more sub-nets. This is great (for example) for large networks that use a significant potion of their private IP space. It's also good for added security, improved performance, and simplified troubleshooting. Subnetting is a achieved through a process which ANDs the binary value of an IP address with another block of 4 octets called the subnet mask to provide a subnet address.
TCP/IP mail services are what one would expect – email. However, it's not quite that cut and dried. SMTP (Simple Mail Transfer Protocol) is the protocol for moving email around, among other things, the Internet. It operates over port 25 and uses a format called MIME (Multipurpose Internet Mail Extensions). MIME was released by the IEEE in 1992 to make email more versatile. Before MIME you couldn't for example, include pictures in an email. (You couldn't include malware, either, but hey, you have to take the bad with the good.) There's also POP (Post Office Protocol) which operates over port 110. Also out there is IMAP (Internet message Access Protocol) which was developed as a more sophisticated option over P POP3. It can replace POP3 without changing programs.
The final portion of the chapter covered utilities like traceroute, host, dig, and netstat that are used for setting up and troubleshooting a network.
Reading this chapter, it finally started to sink in why it's possible to make a living doing this stuff – to a layperson, a lot of this must be dauntingly arcane.
Subnetting is the process by were a single IP address can be split into more sub-nets. This is great (for example) for large networks that use a significant potion of their private IP space. It's also good for added security, improved performance, and simplified troubleshooting. Subnetting is a achieved through a process which ANDs the binary value of an IP address with another block of 4 octets called the subnet mask to provide a subnet address.
TCP/IP mail services are what one would expect – email. However, it's not quite that cut and dried. SMTP (Simple Mail Transfer Protocol) is the protocol for moving email around, among other things, the Internet. It operates over port 25 and uses a format called MIME (Multipurpose Internet Mail Extensions). MIME was released by the IEEE in 1992 to make email more versatile. Before MIME you couldn't for example, include pictures in an email. (You couldn't include malware, either, but hey, you have to take the bad with the good.) There's also POP (Post Office Protocol) which operates over port 110. Also out there is IMAP (Internet message Access Protocol) which was developed as a more sophisticated option over P POP3. It can replace POP3 without changing programs.
The final portion of the chapter covered utilities like traceroute, host, dig, and netstat that are used for setting up and troubleshooting a network.
Reading this chapter, it finally started to sink in why it's possible to make a living doing this stuff – to a layperson, a lot of this must be dauntingly arcane.
Chapter 9: Network operating Systems
This chapter dealt with NOSs. Network Operating Systems aren't that different at their core than a workstation OS – they're a framework that allows a collection of useful programs to be run and also a way of coordinating the transfer of resources around a network. A server can be configured to divide users into groups with different sets of privileges and access to different programs and batches of data, they can function as “super-routers” that can direct network traffic in sophisticated ways, and they can also provide monitoring, reporting, security services, and the like.
While other ones are out there, there are 3 primary flavors of NOS: Windows, UNIX, and Linux. Windows is the entry of Microsoft in this arena, and is probably the most user-friendly of the three. It's equipped with a very nice, intuitive GUI. UNIX is available in both commercial and open-source varieties and has been around in one form or another almost as long as computers have. Linux is an open-source OS that started as an alternative to UNIX but has since branched and grown into its own product. All three are in heavy use in the modern world.
My strongest reaction to this chapter was a strong desire to install and play around with a NOS. I'm hoping to get the chance soon – I'd like to make my home network a bit more sophisticated.
While other ones are out there, there are 3 primary flavors of NOS: Windows, UNIX, and Linux. Windows is the entry of Microsoft in this arena, and is probably the most user-friendly of the three. It's equipped with a very nice, intuitive GUI. UNIX is available in both commercial and open-source varieties and has been around in one form or another almost as long as computers have. Linux is an open-source OS that started as an alternative to UNIX but has since branched and grown into its own product. All three are in heavy use in the modern world.
My strongest reaction to this chapter was a strong desire to install and play around with a NOS. I'm hoping to get the chance soon – I'd like to make my home network a bit more sophisticated.
Saturday, November 21, 2009
Chapter 8: Wireless networking
Chapter 8 covered the various aspects of wireless networking. The chapter led off with a summary of the various frequencies used by wireless networks and spent some time discussing the various things that can cause trouble with wireless signals (anything but air, basically) and from there moved into WLAN architecture. Since WLANs don't have actual cables, their topologies are different than wired networks. It seems to primarily boil down to a P2P style ad hoc configuration or a star-like access point setup, though.
The chapter also spent some time on the IEEE 802.11b, 802.11a, 802.11g and the recently-released 802.11n standards, which govern most wireless networks in use today, and Bluetooth, which covers a sizeable chunk of the remaining ones.
The chapter also covered setting up a WLAN and also went into some detail on satellite data transmission.
Honestly, whenever I see "wireless," I cringe a little bit. It's less secure and less efficient than running cables, and I'm not a huge mobile device user. Still, it's good to know - it's just not my favorite topic.
The chapter also spent some time on the IEEE 802.11b, 802.11a, 802.11g and the recently-released 802.11n standards, which govern most wireless networks in use today, and Bluetooth, which covers a sizeable chunk of the remaining ones.
The chapter also covered setting up a WLAN and also went into some detail on satellite data transmission.
Honestly, whenever I see "wireless," I cringe a little bit. It's less secure and less efficient than running cables, and I'm not a huge mobile device user. Still, it's good to know - it's just not my favorite topic.
Wednesday, November 18, 2009
Chapter 7: WANs and remote connectivity
Chapter 7 covered WANs, or Wide Area Networks. A WAN is a network that spans more than one site. My current employer has a WAN running some proprietary software that spans all of the stores in the company that we use for internal communication and day-to-day operations. WANs have their own topologies, in this case based on sites rather than nodes. Bus, ring, and star are present just like in LANs, and they mean roughly the same thing. A bus is a network where each site is connected to no more than two other sites in a line, a ring is similar to a bus, but the “ends” meet, and a star configuration has a central site to which the others connect. There are also mesh topologies (all the sites are directly connected to each other – high performance and fail safe, but very expensive) and a tiered topology (basically connect several star networks in bus configuration – the central sites basically function as the network's backbone).
The chapter covered the use of PSTN (Public Switched Telephone Network) or, more humorously and appropriately POTS (Plain Old Telephone Service) and its utility in data transmission. As it turns out, there are a number of different ways to get data over phone lines. You've got old, slow, crummy, sad dial-up service, which is about as useful in today's age as a handcart is for moving a battleship. (Then again, it's still better than carrying the battleship by hand...) There's ISDN which is slow and expensive (and not very common, either). There's DSL which is actually pretty nice if you get a high-throughput plan. And then there are T-lines, which used to be the fastest available, but are now getting serious competition from DSL. If you're able to read these words, you know speed is good where data transmission is concerned.
The chapter also covered SONET, a high-speed dual-ring network setup (one going clockwise, the other counterclockwise) over fiber-optic cable. It's exceedingly fault-tolerant and it's also very expensive. The most interesting thing about SONET to me, though, is that there's still a viable use for a ring-topology network in today's world.
Finally, the chapter covered remote access, touching on dial-up networking, remote access servers, and VPNs. The application of these technologies in the real world is obvious – most business travelers now own laptops for the express purpose of being able to access data back at their home office. VPNs also have the additional handy feature of allowing greater security at a public hotspot if used to connect to a more secure system.
I got a kick out of this chapter – I just think it's cool that the old ring topology is still useful in today's world, and reading about the different types of WAN technology was a fun walk down memory lane.
The chapter covered the use of PSTN (Public Switched Telephone Network) or, more humorously and appropriately POTS (Plain Old Telephone Service) and its utility in data transmission. As it turns out, there are a number of different ways to get data over phone lines. You've got old, slow, crummy, sad dial-up service, which is about as useful in today's age as a handcart is for moving a battleship. (Then again, it's still better than carrying the battleship by hand...) There's ISDN which is slow and expensive (and not very common, either). There's DSL which is actually pretty nice if you get a high-throughput plan. And then there are T-lines, which used to be the fastest available, but are now getting serious competition from DSL. If you're able to read these words, you know speed is good where data transmission is concerned.
The chapter also covered SONET, a high-speed dual-ring network setup (one going clockwise, the other counterclockwise) over fiber-optic cable. It's exceedingly fault-tolerant and it's also very expensive. The most interesting thing about SONET to me, though, is that there's still a viable use for a ring-topology network in today's world.
Finally, the chapter covered remote access, touching on dial-up networking, remote access servers, and VPNs. The application of these technologies in the real world is obvious – most business travelers now own laptops for the express purpose of being able to access data back at their home office. VPNs also have the additional handy feature of allowing greater security at a public hotspot if used to connect to a more secure system.
I got a kick out of this chapter – I just think it's cool that the old ring topology is still useful in today's world, and reading about the different types of WAN technology was a fun walk down memory lane.
Chapter 6: Network Hardware
Chapter 6 dealt with the hardware side of things in detail. The first thing the chapter covered was various types of NIC (Network interface Card). NICs come in a dizzying array of different types, and are available for just about every sort of expansion connector known to computing (PCI, PCIe, FireWire, USB, CardBus and ExpressCard for laptops, and built-in ones integrated into the motherboard of a computer) Regardless of how you connect them or what kind of cable (or radio signal) they use, however, a NIC is fundamentally a NIC. They're used to convert data into electrical impulses, light, or radio waves for transmission to the next NIC and for converting those same impulses, light beams, or radio waves back into data when it arrives.
The chapter also covered repeaters, hubs, switches, bridges, and routers. These devices, collectively, form much of the backbone of a network, and perform functions analogous to stoplights and street signs in a city, managing where traffic flows, what gets priority, and that everything (or at least as much as possible) gets there intact. Repeaters and hubs are the simplest, just rebroadcasting whatever comes into them. The biggest difference is that a repeater only broadcasts out to one output, whereas a hub will have several. Hubs have largely become a thing of the past – switches these days are so cheap that you'd be silly not to use one. Switches and bridges connect segments of a network to each other and operate by actually sending packets just to their destination IP rather than just broadcasting them like a hub. Small wonder they're more efficient. Bridges are basically two-port switches, used to connect just two segments together. Routers are like switches on steroids. They have an array of filtering, reporting, and security features built in. They are more than one needs sometimes, but they're great for setting up intra-nets that still connect to the Internet, because they can route traffic from an entire network out to the Internet via a single public IP.
The chapter was useful, but seemed a touch overlong for the material it covered – these connectivity devices are vital but somewhat self-explanatory. Then again, maybe it's just prior knowledge talking.
The chapter also covered repeaters, hubs, switches, bridges, and routers. These devices, collectively, form much of the backbone of a network, and perform functions analogous to stoplights and street signs in a city, managing where traffic flows, what gets priority, and that everything (or at least as much as possible) gets there intact. Repeaters and hubs are the simplest, just rebroadcasting whatever comes into them. The biggest difference is that a repeater only broadcasts out to one output, whereas a hub will have several. Hubs have largely become a thing of the past – switches these days are so cheap that you'd be silly not to use one. Switches and bridges connect segments of a network to each other and operate by actually sending packets just to their destination IP rather than just broadcasting them like a hub. Small wonder they're more efficient. Bridges are basically two-port switches, used to connect just two segments together. Routers are like switches on steroids. They have an array of filtering, reporting, and security features built in. They are more than one needs sometimes, but they're great for setting up intra-nets that still connect to the Internet, because they can route traffic from an entire network out to the Internet via a single public IP.
The chapter was useful, but seemed a touch overlong for the material it covered – these connectivity devices are vital but somewhat self-explanatory. Then again, maybe it's just prior knowledge talking.
Chapter 5: Network Topologies
Chapter 5: Network Topologies
This chapter dealt with the physical layout of networks, and when you boil it down, there aren't many of those. The three basic types of network are bus (computers set up in-line, passing data down the line bucket-brigade style), ring (like a bus, but the ends are linked, so data won't always have to travel so far) and star (all of the nodes are connected to a central device of some sort, which coordinates traffic out to the individual nodes). Of the three, star is by far the most common in the modern world, which makes sense. A star network is a typical client/server network, and is also the most efficient type of network, especially considering the power of modern computers.
You still see the other types, though. Connecting an ipod to a computer temporarily creates a small bus-style network, and ISPs often use a high-speed double ring network called SONET. You'll also see what are called hybrid networks, which most commonly result from connecting two networks of different types together.
The chapter also covered what's known as a network backbone, which is another way of describing all the connectivity devices on a network. Things like hubs, switches, and routers form a network's backbone, though a more accurate term might have been “spinal cord.” They function in much the same way as a spinal cord does, passing data around the network and allowing one node to communicate with another efficiently. Also much like a spinal cod, they don't generate any information themselves most of the time; rather they just insure that existing data gets where it needs to.
The chapter also covered various types of Ethernet standards (my word we've come a long way in a short time...) and useful technologies such as Power Over Ethernet, which a friend of mine who works IT for a large medical company swears by. Apparently, PoE is great for powering touch screen terminals in medical labs.
An interesting chapter, overall. In particular, it was neat to find out about some of the ways networks have grow and changed over the years. We've come a LONG way from the old token ring networks.
This chapter dealt with the physical layout of networks, and when you boil it down, there aren't many of those. The three basic types of network are bus (computers set up in-line, passing data down the line bucket-brigade style), ring (like a bus, but the ends are linked, so data won't always have to travel so far) and star (all of the nodes are connected to a central device of some sort, which coordinates traffic out to the individual nodes). Of the three, star is by far the most common in the modern world, which makes sense. A star network is a typical client/server network, and is also the most efficient type of network, especially considering the power of modern computers.
You still see the other types, though. Connecting an ipod to a computer temporarily creates a small bus-style network, and ISPs often use a high-speed double ring network called SONET. You'll also see what are called hybrid networks, which most commonly result from connecting two networks of different types together.
The chapter also covered what's known as a network backbone, which is another way of describing all the connectivity devices on a network. Things like hubs, switches, and routers form a network's backbone, though a more accurate term might have been “spinal cord.” They function in much the same way as a spinal cord does, passing data around the network and allowing one node to communicate with another efficiently. Also much like a spinal cod, they don't generate any information themselves most of the time; rather they just insure that existing data gets where it needs to.
The chapter also covered various types of Ethernet standards (my word we've come a long way in a short time...) and useful technologies such as Power Over Ethernet, which a friend of mine who works IT for a large medical company swears by. Apparently, PoE is great for powering touch screen terminals in medical labs.
An interesting chapter, overall. In particular, it was neat to find out about some of the ways networks have grow and changed over the years. We've come a LONG way from the old token ring networks.
Sunday, November 1, 2009
Chapter 4: TCP/IP
Note: I give. Trying to make this a "real blog" with NaNoWriMo, a second class, and the busiest time of year at work (I work in retail - one of the reasons for taking this class in the first place - so I can get into a career field that's more cerebral and more lucrative) pressing down on me is proving to be a bit too much. Until I get caught up, these blog posts are going to be much shorter and less in-depth than the previous ones. If I get a chance, I may go back and crank them up to a higher level, but for now, I just need to complete the assignments.
TCP/IP is the suite of protocols that most modern networks (including the internet) run on. However, despite the name, it's more than just TCP and IP - the suite also includes protocols like UDP (useful in applications like VOIP) and the ARP/RARP protocols used for address resolution. Basically, TCP/IP is the language that allows a network to communicate. TCP and UDP to move data around, ARP and RARP to establish addressing, ICMP to report any problems with the path the packets are taking, and so forth.
The chapter also covered addressing. The web currently runs on IPv4 (an IPv4 address looks like this: 192.168.24.130) this is all well and good, but the addresses are getting used up at a rapid pace. One solution to this is IPv6, which has a lot more available address space (79,228,162,514,264,337,593,543,950,336 unique addresses as opposed to IPv4's approximately 4.3 billion, to be precise). One stopgap measure that's been used is private network IPs, which means that you can re-use a block of IPs as long as they're not connected to the larger internet. My router at home, for example, uses the 192.168.x.x IP space. So does everybody else who uses that type of router's network. The router itself, however, uses a public IP issues by my internet service provider.
The chapter also covered DNS or Domain Name Service, which is nothing more, and nothing less, than the process which turns www.mchenry.edu into the IP address that will direct my web browser to the college's web page.
An interesting chapter from a theoretical point of view. I was dimly aware of TCP/IP, DNS and the like when I started reading (thanks largely to the early episodes of Security Now) but this got a lot more in depth.
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