We talked about the basic operations of DHCP in our previous blog post, "What is DHCP?”. Today, we will find out what kind of agent a DHCP relay agent is. Generally, DHCP messages are broadcasted. So, in order for the messages to be exchanged between a DHCP client (PC) and DHCP server, both the client and server have to reside on the same subnet. That is because routers do not fo...

As we need a phone number to make a call to someone, we need an address to communicate with a network host over the Internet. This address is called an "Internet Protocol (IP) address". Generally, IP addresses are dynamically allocated to clients accessing the Internet, through Dynamic Host Configuration Protocol (DHCP), a protocol designed for dynamic allocation of IP addresses, as defined in...

Now that we know what DHCP relay agents are, we will find out another DHCP agent, a DHCP proxy agent today. What a DHCP relay agent does is simply relay broadcast DHCP packets (DHCP Discover/Request) to DHCP server(s) located in other subnets whenever it receives packets from a DHCP client residing in that same subnet. On the other hand, a DHCP proxy agent not only relays the DHCP packets...

We will look into DHCP Option 82 used in the wireline networks of network operators today. Most of you are probably subscribing to a wireline Internet service provided by one of the network operators such as KT, SK Telecom or LGU+ (Korean Operators). When users subscribe to the Internet service, they pay a monthly fee to their network operator for using the Internet service. So, as a genera...

Last time when we introduced a DHCP proxy agent through our previous blog post dated in September 1. 2013, we mentioned that this DHCP proxy agent can offer the benefits of enhanced security. So, we will look into these security-related functions in more detail today. As shown in the figure below, if there is a DHCP proxy agent in a network, all DHCP messages (used in IP address allocation...

We are pleased to share with you all an interesting article contributed by Reza Toghraee. Reza Toghraee Technical Manager (CCIE, Cloud, SDN, Netwrok, Security Expert) at ArpaWare All Articles by Reza Toghraee...

As noted in the previous post, currently there are two types of user authentication in the Wi-Fi networks operated by Korean operators: IEEE 802.1X-based and captive portal-based authentication. 802.1X-based authentication targets primarily mobile devices with an operator's USIM card, whereas captive portal-based authentication to be discussed here is used to attract users without a permane...

We will talk about call flow in IEEE 802.1X-based user authentication used in Korean network operators' Wi-Fi networks. Before we continue, let's take a look at what Korean operators' current Wi-Fi authentication are like first. KT provides the following SSIDs in its Wi-Fi Hotspots: ollehWiFi (with lock icon): Users are authenticated based on the IMSI stored in USIM of their...

Switching and Routing 1. Switching and Routing for Dummies - Ethernet Switching 2. Switching and Routing for Dummies - IP Routing 3. Switching and Routing - Part 1. Router Architecture 4. Switching and Routing - Part 2. Packet Forwarding by IP Router 5. Switching and Routing - Part 3. L2 (Ethernet) Switching by L3 Switch 6. Switching...

For the past year or so, you have probably heard of CORD, which stands for Central Office Re-architected as a Datacenter. CORD was developed by AT&T with the aim to transform conventional Central Offices (COs) in operators' networks into something similar to data centers of cloud service providers. AT&T, having conducted POCs and demonstrations on CORD architecture at its lab since las...

Switching and Routing 1. Switching and Routing for Dummies - Ethernet Switching 2. Switching and Routing for Dummies - IP Routing 3. Switching and Routing - Part 1. Router Architecture 4. Switching and Routing - Part 2. Packet Forwarding by IP Router 5. Switching and Routing - Part 3. L2 (Ethernet) Switching by L3 Switch 6. Switching...

Obviously, the hottest issue in mobile communication today is LTE. All three top telecommunication operators in Korea are trying hard to promote their brands, each containing the technical term "LTE" somewhere, for greater exposure of the brands to the public. So, we will briefly go over what network elements make the LTE network today. The Figure below is an illustration of an LTE Network R...