I recently started working on an issue that I’d seen was to do with the HSS response to the MME on an Update Location Answer. I took some Wireshark traces of a connection from the MME to the HSS, and compared that to a trace from a different HSS. (Amarisoft EPC/HSS) The Update Location Answer […]
The packet structure of Diameter
A primer to the Diameter protocol and it’s usage.
ARP in LTE is not the Ethernet standard for address resolution, but rather the Allocation and Retention Policy. A scenario may arise where on a congested cell another bearer is requested to be setup. The P-GW, S-GW or eNB have to make a decision to either drop an existing bearer, or to refuse the request […]
MBR stands for Maximum Bit Rate, and it defines the maximum rate traffic can flow between a UE and the network. It can be defined on several levels: MBR per Bearer This is the maximum bit rate per bearer, this rate can be exceeded but if it is exceeded it’s QoS (QCI) values for the […]
The QCI (Quality Class Indicator) is a value of 0-9 to denote the service type and the maximum delays, packet loss and throughput the service requires. Different data flows have different service requirements, let’s look at some examples: A VoLTE call requires low latency and low packet loss, without low latency it’ll be impossible to […]
GBR is a confusing concept at the start when looking at LTE but it’s actually kind of simple when we break it down. GBR stands for Guaranteed Bit Rate, meaning the UE is guaranteed a set bit rate for the bearer. The default bearer is always a non-GBR bearer, with best effort data rates. Let’s […]
Adding online map tiles in Forsk Atoll
We’ve already touched on how subscribers are authenticated to the network, how the network is authenticated to subscribers and how the key hierarchy works for encryption of user data and control plane data. If the IMSI was broadcast in the clear over the air, anyone listening would have the unique identifier of the subscriber nearby […]
We’ve talked a bit in the past few posts about keys, K and all it’s derivatives, such as Kenc, Kint, etc. Each of these is derived from our single secret key K, known only to the HSS and the USIM. To minimise the load on the HSS, the HSS transfers some of the key management […]
We’ve already touched on how subscribers are authenticated to the network, how the network is authenticated to subscribers. Those functions are done “in the clear” meaning anyone listening can get a copy of the data transmitted, and responses could be spoofed or faked. To prevent this, we want to ensure the data is ciphered (encrypted) […]
How LTE Subscriber authenticate the network
LTE/4G’s use of RAND and K to verify subscribers identity.
Contents of a USIM, fields & their meanings and basics of EUTRAN authentication.
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. Let’s look at how the Tracking Area Updates work from the point of view of the network. Let’s take an example of a […]
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. As we’ve seen earlier, the eNB needs a connection to an MME and a S-GW. However different eNBs may connect to different S-GWs […]
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. As we saw before larger Tracking Areas minimize the number of UEs between terminals to update their location. The problem is the cells/eNBs […]
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. As we saw with the Network Triggered Service Request, the network needs to know which eNB / cell the UE is currently being […]
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. As we discussed before when no data has been sent by a UE for a period of time the eNB will switch from […]
These are my lecture notes from IMT’s NET02x (4G Network Essentials) course, I thought I’d post them here as they may be useful to someone. You can find my complete notes here. As we just saw when a terminal moves to ECC-Idle while in EMM-Registered state, it releases it’s radio resources, so what happens when […]