Google Global Caches (GGCs) have already been deployed in many telecom operators' data centers around the world, caching YouTube video files like Psy's Gangnam Style for the local users. This allows people around the globe to watch Psy singing and dancing without buffering through their local GGCs. Korean operators like SK Telecom, LG U+ and KINX have also made the same move in February...

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...

This post will analyze the streaming methods used in YouTube's Live TV streaming services for mobile devices in an LTE network and a Wi-Fi network based on our actual measurements. YouTube's Live TV Streaming in Mobile Devices: HLS & Adaptive First, measurements in an LTE network The mobile device and network used for our measurement were Galaxy S4 and KT LTE network. First,...

In the last two posts (Part 1, Part 2), we learned about LTE QoS. Now, we will show you an example of controlling P2P traffic using the LTE QoS in the LTE network. Let's say there is a network operator named "NMC Telecom", and it offers a service plan with the following features: No bandwidth limitation for Internet usage Data rate limitation (512 Kbps for download, and 128 Kbps fo...

We will look a little bit further into LTE QoS that we discussed last time, and learn what QoS parameters are for. There are two types of EPS bearers: default and dedicated. In the LTE network, the EPS bearer QoS is controlled using the following LTE QoS parameters: ▶ Resource Type: GBR or Non-GBR ▶ QoS Parameters QCI ARP GBR MBR APN-AMBR UE-AMBR Every EPS bearer must...

Recently, YouTube has changed/evolved the way it delivers video contents. It used to be a big fan of HTTP progressive download (downloading a video file by a single request just like downloading a data file) until last year. However, from this year, many efforts have been made by YouTube (e.g. switching to chunking and adaptive streaming) for improved video delivery. We will focus on "switching...

We will talk about LTE QoS this time. QoS functions provided by any network, whether wired or wireless, are all based on standards (IETF RFC, IEEE 802, 3GPP TS, etc.). They may work differently using different standards depending on whether the network is wired (Ethernet/IP/MPLS) or wireless (LTE/WiBro/Wi-Fi). But, basically what the QoS is about is that traffic quality is guaranteed (i) if...

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...

Today, we will find more about LTE GTP tunnels that we have discussed previously. In the Figure below, GTP tunnels are established in the link from the eNB to the S-GW and from the S-GW to the P-GW. Downlink (DL): From PDN (Internet) to UE [1] A packet (Source IP=www.google.com, Destination IP=UE) is sent from the Internet to the P-GW. [2] The P-GW compares the five tuples of...

SK Telecom, the Korean No. 1 telecom operator, launched Btv Mobile service (in SD/HD) offering a variety of live broadcasting and VoD contents for mobile devices in around July 2012. And a year later in July 2013, boosted by the commercialization of LTE-A, it began a "Full HD" streaming service with drastically enhanced video quality. The following is the press release by SK Telecom about its n...

Today, we will talk about GTP tunnels used in the LTE network. As seen in Figure (a) below, IP packets sent by an LTE device (UE) are delivered from an eNB to a P-GW through GTP tunnels. What it means is that "all IP packets that a UE sends are always delivered through an eNB to a P-GW regardless of their specified destination IP addresses (i.e., even though their destination IP addresses a...

In our previous post (Analysis of LG U+'s HDTV Streaming (LG U+ HDTV Service based on LTE-A), we discussed how LG U+ Mobile U+ HDTV service delivers video files to a device. Our first actual measurement confirmed that LG U+: used HLS, Apple's adaptive streaming (delivering video files chunkwise, unlike progressive download or RTMP/RTSP); and offered three profiles (quality levels)...

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...

This time we will give you a brief overview of an LTE Tracking Area (TA) and Tracking Area Update (TAU). While an LTE device (UE) is in active state (i.e. while communicating, or while in EMM-Registered/ECM-Connected/RRC-Connected state in LTE terms), its location is known by the LTE network at cell level (i.e. on a cell granularity), e.g. in cell2 in eNB1. However, while the UE is in idle...

On June 10, 2013, LG U+ launched U+ HDTV multi-channel service (U+ tv G 4 Channel Service) that enables users to watch 4 channels at the same time through home STB. Later in July, it introduced the same multi-channel service in a mobile version based on LTE-A. In this post, we will analyze the U+ HDTV streaming on mobile devices that support LTE-A. U+ HDTV service offers two viewing experi...

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...

Today's topic is IMSI (International Mobile Subscriber Identity) and GUTI (Globally Unique Temporary Identifier). These two are parameters (identifiers) used in identifying UEs in LTE networks. What is IMSI? IMSI is a unique ID that globally identifies a mobile subscriber. It is composed of two parts, PLMN ID and MSIN, as shown in Figure below. A PLMN ID is an ID that globally identi...

All wireless telecommunication networks (e.g. Wi-Fi, WiBro and LTE provide “user authentication” and “security over radio link (integrity check (protection/verification) and ciphering (or encryption))” features. User authentication is required for network operators to ensure that only those who subscribe to them (i.e. paid subscribers) can access their networks. In wir...

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...

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...