Chapter 1 Flashcards
(42 cards)
What is a network protocol?
A network protocol is a set of rules that define the format and order of messages exchanged between two or more communicating entities, as well as the actions taken on message transmission and reception.
What is store-and-forward transmission
each packet switch receives an entire packet before forwarding it to the next hop.
How is transmission delay in a packet-switched network calculated?
Transmission delay is the time required to push all bits of a packet onto the link and is calculated as:
TransmissionDelay = PacketLength(L)inbits/TransmissionRate(R)inbitspersecond
- For example, if a 1000-bit packet is transmitted on a 10 Mbps link, the transmission delay is 100 µs.
Why does queueing delay occur in packet-switched networks?
Queueing delay occurs when a packet arrives at a router that is already processing other packets. It has to wait in a buffer (queue) until earlier packets are transmitted.
What factors influence queueing delay in a packet-switched network?
- Traffic load – Higher traffic increases waiting time.
- Link capacity – If the link is slow, packets take longer to process.
- Packet arrival rate – If packets arrive faster than they can be transmitted, the queue builds up.
Why does packet loss occur in a packet-switched network?
Packet loss occurs when a router’s buffer (queue) is full and cannot store any more packets, causing new incoming packets to be dropped.
How do routing protocols impact forwarding?
Routing protocols (such as OSPF, BGP) help determine optimal paths for packets by exchanging information between routers. This information is used to update forwarding tables, ensuring packets take efficient routes.
What are the four main components of end-to-end delay in a packet-switched network?
- Processing delay – Time for routers to process the packet header.
- Queueing delay – Time waiting in the router’s queue.
- Transmission delay – Time to push the packet onto the link.
- Propagation delay – Time for the packet to travel across the physical link.
What are Access ISPs and what role do they play in the Internet?
Access ISPs provide end users (homes, businesses, and institutions) with connectivity to the Internet through wired or wireless technologies.
What are Regional ISPs, and how do they fit into the Internet structure?
Regional ISPs connect multiple Access ISPs and provide an intermediate level of connectivity between Access ISPs and Tier-1 ISPs.
What are Tier-1 ISPs, and why are they important?
Tier-1 ISPs (e.g., AT&T, Level 3) form the backbone of the Internet, interconnecting large regions and countries. They do not pay other ISPs for connectivity but instead peer with each other.
What are Internet Exchange Points (IXPs)?
IXPs are physical locations where multiple ISPs interconnect to exchange traffic efficiently, reducing reliance on Tier-1 ISPs.
What are Content Provider Networks, and how do they influence Internet traffic?
Companies like Google, Netflix, and Facebook build their own private networks to deliver content efficiently by bypassing traditional ISPs and connecting directly to IXPs and access ISPs.
How do content providers reduce costs in the Internet structure?
By peering directly with ISPs and using CDNs (Content Delivery Networks) to cache content closer to users, reducing transit costs and improving speed.
What are the types of delay in a packet-switched network?
Processing Delay, Queuing Delay, Transmission Delay, and Propagation Delay
What is Processing Delay?
Time taken by a router to examine a packet’s header and determine where to forward it.
What is Queuing Delay?
Time a packet spends waiting in a router’s queue before being transmitted.
What is Transmission Delay
Time required to push all the packet’s bits onto the link.
What is Propagation Delay
Time for a bit to travel from the sender to the receiver over the physical medium.
Under what conditions does Processing Delay become more prominent?
Significant when packets require deep inspection or filtering (e.g., firewalls).
Under what conditions does Queuing Delay become more prominent?
High when traffic intensity (utilization) is high and link congestion occurs.
Under what conditions does Transmission Delay become more prominent?
Higher for large packets on low-bandwidth links.
Under what conditions does Propagation Delay become more prominent?
Dominates in long-distance links (e.g., satellite communication).
How is traffic intensity defined, and how does it relate to queuing delay?
-Traffic Intensity (I) = (La) / R, where:
L = packet length (bits)
a = average packet arrival rate (packets/sec)
R = transmission rate
-Relation to Queuing Delay:
If I < 1, queuing delay is low.
If I approaches 1, queuing delay increases significantly.
If I > 1, the queue builds up indefinitely, leading to packet loss.