The Internet Protocol (IP) provides a "best-effort" delivery service. This fundamental characteristic means that while IP routers and networks strive to deliver every packet, they offer no inherent guarantees regarding:

• Reliability: Packets may be lost during transit due to network congestion, link errors, or router buffer overflows.
• Ordering: Packets might arrive at the destination out of the original sequence in which they were sent, as different packets may take different paths through the network.
• Timing/Delay: There are no guarantees on the time it takes for a packet to travel from source to destination. This leads to variable delays, a phenomenon known as "jitter."
• Congestion Control: The IP layer itself does not inherently provide mechanisms to prevent or react to network congestion.

Impact: When media data packets are lost, the consequence is missing information that directly translates to noticeable playback degradation. For audio streams, lost packets can lead to audible clicks, pops, temporary silences, or garbled sound. For video streams, missing frames can result in frozen images, visual artifacts (e.g., pixelation, blockiness), or momentary black or green screens, severely disrupting the visual flow.
Causes: The primary causes of packet loss are network congestion (router buffers overflowing), errors on physical transmission links, or corrupted packets being discarded. For real-time media, attempting to retransmit lost packets (as TCP would do) often introduces unacceptable delays, making reliability a secondary concern to timely delivery.

Impact: Jitter refers to the variation in packet arrival times. Even if all packets eventually arrive, if their inter-arrival times fluctuate significantly, the media player's playback buffer can be severely affected. If packets arrive too slowly or too late, the buffer may underflow, leading to playback stuttering, freezes, or re-buffering events. If packets arrive too quickly, the buffer might overflow, causing packet drops at the receiver end. Causes: Jitter primarily arises from varying queueing delays within routers and switches along the network path, different packets taking slightly different routes, and dynamic changes in network load.

Impact: This is the total time taken for a media frame to travel from its source (e.g., a live camera) to its playback point at the destination. While some initial delay for buffering is acceptable, excessive end-to-end latency is detrimental, particularly for interactive live streaming applications like video conferencing or online gaming. High latency makes natural conversation difficult and real-time responsiveness impossible. Even for on-demand streaming, a long initial startup delay can negatively impact user satisfaction. Causes: End-to-end delay is an accumulation of various factors: propagation delay (time for signal to travel across physical medium), transmission delay (time to put bits onto the wire), queuing delay (time spent waiting in router queues), processing delay (time for routers to process packet headers), and critically, buffering delay (time spent accumulating data in the client's buffer).

Impact: The available network bandwidth between the streaming server and the client is rarely static. It can fluctuate significantly due to other network traffic from the user's home or office, changes in wireless signal strength, or even deliberate throttling by ISPs. If the effective available bandwidth drops below the media's encoded bitrate, the client's buffer will rapidly deplete, resulting in frequent and disruptive re-buffering events (the dreaded "spinning wheel" or "loading" indicator). Causes: Competing traffic on local networks, wireless interference, internet congestion upstream, or ISP network management policies.

Impact: When network links or intermediate routers become overloaded with too much traffic, their buffers overflow, leading to severe packet loss, increased delays, and exacerbated jitter. These conditions collectively result in a drastic degradation of streaming quality, leading to frequent interruptions, low resolution, and poor audio. Causes: Exceeding the capacity of network links, sudden bursts of traffic, or inefficient network traffic management.

Impact: Firewalls, which control network traffic based on security rules, and NATs, which allow multiple devices on a private network to share a single public IP address, are essential for security and IP address conservation. However, they can pose challenges for certain streaming protocols, especially those that attempt to establish direct peer-to-peer connections or use non-standard ports. Firewalls often block unsolicited incoming connections, and NATs can complicate the addressing of peers behind them, making it difficult for streaming data to reach the client correctly. Causes: Default security policies of firewalls, and the remapping of IP addresses and ports by NAT devices.