Term
|
Definition
| Layering of protocols is used to simply complex data packets into simpler smaller functions. |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
| Defines network interfaces between network nodes. Uses ethernet protocol |
|
|
Term
|
Definition
Provides universal and consistent forwarding services across TCP/IP network. End-to-end addressing and carrying of data packets from source to destination.
Router forwards data on hop-by-hop basis. |
|
|
Term
|
Definition
| Utilizes TCP/IP to break information into smaller segments and transports from end-to-end |
|
|
Term
| Which layer uses routing protocols for path determination |
|
Definition
|
|
Term
| Describe source/destination information for each layer |
|
Definition
1. Link layer uses source/destination MAC address
2. Internet layer uses source/destination IP address
3. Transport layer uses source/destination port number |
|
|
Term
|
Definition
| Mechanism which a protocol stacks layered header information as the data packet moves down the layer |
|
|
Term
|
Definition
| The removal of header information by protocols as data packet moves up the layer. |
|
|
Term
| Which device is used at which level |
|
Definition
1. Switch = Link layer
2. Router = internet layer
3. host = application layer |
|
|
Term
|
Definition
| A switch forwards L2 data fram based on the destination MAC address |
|
|
Term
|
Definition
| A router examines the L2 MAC address and forwards the ip packet based on the destination IP address. It replaces the source and destination MAC with new addresses |
|
|
Term
|
Definition
| All hosts are on the same LAN. Switch is used to make forwarding decision using MAC address. IP addresses have same prefix. |
|
|
Term
|
Definition
| Two or more L2 broadcast domains connected via router |
|
|
Term
|
Definition
| Virtual Private Network. Network overlay created specifically for a customer that is isolated from other traffic. Uses tunneling technique to carry traffic (MPLS,VXLAN, segment-routing...) |
|
|
Term
|
Definition
| Enable routers to exchange control messages and agree on best way to forward packets. Establish necessary routing paths/tunnels. |
|
|
Term
|
Definition
| Use forwarding tables from control plane function to forward data packets |
|
|
Term
| Typical Service Provider Network Architecture |
|
Definition
Access nodes: Doesn't need to be high capacity but needs to be compatible with customer technology
Aggregation nodes: higher capacity to improve scalability by aggregating traffic into lesser streams
Edge nodes: High capacity reciving traffic from many aggregation nodes. Provide customers with connectivity services.
Core Nodes: Very high capacity as they carry huge amounts of traffic from one site to another |
|
|
Term
| Example of Nokia products in end-to-end solution |
|
Definition
service access: 7705 or 7210
service aggregation: 7250 or a 7750
Provider edge: 7750
Core: 7950 |
|
|
Term
| Optical transport network |
|
Definition
| Routers far apart use optical switches using wavelength-division multiplexing (WDM) signals. Optical transport network is capabale of carrying high-bandwidth signals over long distances. |
|
|
Term
| Wavelength-Division multiplexing (WDM) |
|
Definition
| Transports multiple optical signals on a single fiber. Ethernet frames transmitted by routers are put into OTN frames |
|
|
Term
|
Definition
| 8 channels per fiber, used in access and metro networks. Carries up to 80 km |
|
|
Term
|
Definition
| 128 or more channels per fiber. Used in regional and core networks. Carries up to thousands of kilometers |
|
|
Term
| How data moves into and out of a router |
|
Definition
| Data is recieved by I/O card. Data can either be sent from I/O card to CPM (central processing module) or sent to another I/O card for exiting. |
|
|
Term
|
Definition
| A switch fabric allows data packets to move from ingress I/O card to egress I/O card. It also allows packet to move to and from the CPM |
|
|
Term
|
Definition
| A hot-swappable module that integrates the SF and the CPM in one card. Provides both data plane and control plane functionality |
|
|
Term
|
Definition
Same functionality as an integrated SF/CPM except they are seperate cards where the CPM is a pluggable module and the SF is the base.
Found on Nokia 7750 SR-12 chassis |
|
|
Term
|
Definition
Hot swappable module that contain two traffic-processing programming FP complexes which each support a pluggable MDA allowing for support of all possible interface types. Each IOM also contains a CPU to manage forwarding hardware.
Can contain 2-6 MDAs |
|
|
Term
| MDA (Media Dependent Adapters) |
|
Definition
| Interfaces situated in the IOM that pass incoming frames to the IOM for processing and transmit outgoing frames to the physical interface. |
|
|
Term
| Integrated Media Module (IMM) |
|
Definition
| Card that integrates processing and physical interface in a single card (IOM and MDA combined into a single card). |
|
|
Term
| eXpandable Media Adapter (XMA) |
|
Definition
| Similar to IMM but each card includes multiple FP4 network processors for increasing processing power. |
|
|
Term
| XMA Controller Module (XCM) |
|
Definition
| Base card that XMAs plug into providing necessary connectvity to SF. |
|
|
Term
| Order of components in IOM/MDA |
|
Definition
| IOM contains the MDA which contains the SFP/CFP optics. Traffic movies into SFP to MDA to IOM to SF/CPM back to IOM, MDA, and then SFP/CFP on the way out |
|
|
Term
Which of the following shows a typical data packet flow
when egressing an Nokia 7750 SR?
a. SF/CPM -> MDA -> IOM -> SFP
b. SF/CPM -> SFP -> IOM -> MDA
c. SF/CPM -> IOM -> MDA -> SFP
d. MDA -> IOM -> SF/CPM -> SFP |
|
Definition
| C - SF/CPM -> IOM -> MDA -> SFP |
|
|
Term
|
Definition
Rather than using I/O cards, you use can use I/O slots for specialized cards to do extra processing
MS-ISA (integrated service adapter) can be plugged into IOM.
MS-ESA (extended service appliance) can be installed where XMA would be. |
|
|
Term
|
Definition
| Each CPM module has 3 CF slots. System start-up checks and system files are on cf3. |
|
|
Term
|
Definition
1. Boot Loader File (boot.ldr) - image file that runs hardware initialization
2. Boot options file (bof.cfg) - commands for basic router configuration
3. Software image directory (TiMOS-m.n.Yz) - Where the software image for the OS is
4. Configuration file (config.cfg) - commands requires to get router into a desired operational state |
|
|
Term
| Files in a redudant system with SF/CPM and IOM |
|
Definition
cpm.tim
iom.tim
support.tim |
|
|
Term
| Files in a non-redundant system with integrated fabric/control and I/O card |
|
Definition
|
|
Term
|
Definition
Bof should contain primary software image location, primary configuration file location, and ip address of ethernet management port.
A router with two CPM cards will each have their own management IP address |
|
|
Term
|
Definition
1. Load and run boot.ldr file
2. Read bof.cfg file
3. Load the software image file
4. Execute configuration file and commands in it |
|
|
Term
|
Definition
| Tree-shaped data structure with complete set of configuration information to get device to operational state |
|
|
Term
|
Definition
| Tree-shaped data structure which holds statistical information. |
|
|
Term
|
Definition
Configuration with multiple changes should be activated as a whole (all-or-none) and at specific moment in time.
Multiple datastores - configuration changes stored in a candidate configuration datastore which becomes activing by commiting the candidate configuration. |
|
|
Term
| Configuration modes in MD-CLI |
|
Definition
Global - users see and modify global candidate configuration in non-exclusive mode
Exclusive - users modify global candidate configuration in exclusive mode
Read-only - users can see changes being made by other users
Private - users create their own private candidate configuration in exclusive mode |
|
|
Term
| Global Candidate configuration |
|
Definition
| Multiple users can enter global configuration mode concurrantly. If users are in global mode, no one can enter exclusive mode. If user is in exclusive mode, then only read-only mode is available. |
|
|
Term
| Private candidate configuration |
|
Definition
| A running configuration is copied into private mode as a baseline. If the running configuration is modified, an exclamation mark will show it as out of date. Update merges the running datastore to a new baseline. |
|
|
Term
| Commits to candidate configuration |
|
Definition
Global mode - any commits are committed to running configuration
Exclusive mode - only user in exclusive mode can commit to running configuration
Read-only mode - user cannot commit changes
Private mode - only user can commit changes in private to running configuration |
|
|
Term
|
Definition
Control generation and recording of messages describing system events.
Security: Breach in system security
Change: Changes to configuration
Debug: Generated by debug command
Main: non-associated events |
|
|
Term
|
Definition
Console
CLI
File (not cf3)
Memory
Syslog
SNMP
NETCONF
Use cf1 or cf2 |
|
|
Term
|
Definition
ID is 1 to 101 for an event log
Log 99 - registers all severity levels
Log 100 - registers severty of major/critical
Log 98 - used for SNMP logs
Log 101 - used for NETCONF logs |
|
|
Term
| What are the main functions of the control plane? |
|
Definition
| To build the forwarding table and handle routing for data packet. |
|
|
Term
| What are the main functions of the data plane |
|
Definition
| To use the forwarding table from the control plane to receive, process, and send traffic |
|
|
Term
| What does bof.cfg contain? |
|
Definition
| It contains location of the software image, location of the configuration file, and management IP address and ethernet port |
|
|
Term
|
Definition
|
|
Term
| How many default logs are there, and what do they provide? |
|
Definition
Log 98 - SNMP
Log 99-100 - Main events
Log 101 - NETCONF |
|
|
Term
| What is the management data store and how many types are there? |
|
Definition
A tree like structure that holds the configuration information.
Two types - configuration and state |
|
|
Term
If CLI is configured as MD, which engines are authorized?
Mixed?
Classic? |
|
Definition
Mixed/MD - both classic and MD are authorized
Classic - only classic is authorized |
|
|
Term
| What are the MD edit modes? |
|
Definition
Global
Exclusive
Read-Only
Private |
|
|
Term
| Which candidate configuration datastore do you access in each edit mode? |
|
Definition
Global - access to global datastore
Exclusive - access to global datastore
Read-only - read access to global datastore
Private - access to private datastore |
|
|
Term
| How many users can concurrently enter each configuration mode? |
|
Definition
Global - all users
Exclusive - only user in exclusive mode
Read-Only - all users
Private - any user can enter their own private mode |
|
|
Term
| What is the protocol used in the link layer (L2)? |
|
Definition
|
|
Term
|
Definition
Describes how two nodes can successfully transmit data concurrently to each other
Full duplex - simultaneous bidirectional transmission
Half duplex - only one node can transmit at a time |
|
|
Term
|
Definition
100BASE-T vs 100BASE-SX,LX,EX,ZX
First part of the name is the rate in Mbps or Gbps.
Next part is BASE which means baseband modulation
Last part is the medium which signals move along. "T" means twisted copper cables. Other letters indicate optical-fiber option |
|
|
Term
|
Definition
Directly connected ethernet nodes negotiate their speed and duplex mode prior to establishing a link.
It is better to manually set speed and mode for nodes rather than using auto-negotiation. |
|
|
Term
|
Definition
How hosts on a LAN talk to each other.
BUS - multiple hosts connected to same physical medium - compete to transmit
CSMA-CD: Carrier Sense Multiple Access with Collision Detection - host senses medium and will not transmit if being used by another. Collision detection will stop host transmission if detected (less efficient as host has to sense medium) - half duplex only
P2P (point-to-point) - eliminates collision by providing separate physical links to eliminate collision and allow full-duplex |
|
|
Term
|
Definition
L2 device that replicates frame as soon as it arrives so all hosts recieve a copy
CSMA/CD used for hubs to reduce collision |
|
|
Term
|
Definition
| Smart device that only forwards frames if safe to do so. Transmission on one interface is independent from transmission on another. A switch reduces collision by created multiple independent collision domains. |
|
|
Term
|
Definition
MAC address is 48 bits in 12 hexadecimal digits.
First 6 digits are for the organizationally unique id (OUI) - vendor of the nodes
Last 6 digits are uniquely assigned by the vendor |
|
|
Term
|
Definition
Address assigned to physical interface. A unicast destination is meant for a specific host
For destination node, only the one with matching MAC address will accept the fram |
|
|
Term
|
Definition
address is ff:ff:ff:ff:ff:ff. This destination address is used for all hosts on LAN
All hosts will accept the frame if this is the destination address |
|
|
Term
|
Definition
OUI value is 01:00:5e and 25th bit is 0. Destination address is used when frame meant for specific hosts on a multicast group
Sometimes a multicast group can accept frames from other groups due to overlap. |
|
|
Term
| Forwarding Database (FDB) |
|
Definition
Table maintained by switch with each unicast MAC address and port that it can reach.
Entries are added as incoming frames are received by the switch and the source MAC address and port is stored.
If destination of frame is not known in the FDB then the switch will flood the hosts. When the correct host responds, the switch will store the information in its FDB.
Eventually FDB will fill and the switch will know all hosts MAC addresses and ports |
|
|
Term
| True or False, BUM MAC addresses (broadcast, unknown unicast, multicast) are added to the FDB |
|
Definition
| False - since no specific host is associated with these MAC addresses, they are not added to the FDB. Instead the switch floods the hosts with these frames. |
|
|
Term
|
Definition
Also known as a LAN. All hosts are interconnected via hubs and switches.
Can include multiple collision domains. CD exists between switches and host and between two switches |
|
|
Term
|
Definition
Preamble and start-of-frame delimiter: 56 bits allowing transmitter/receiver to synchronize
Destination : MAC address of destination host (not necessarily final destination)
Source: MAC address of transmitting host
Type: Ethertype - type of payload being carried (IPv4, IPv6, MPLS...)
Payload: Where the IP header would be if IP running over ethernet
Frame check sequence: Verifies information is not damaged during transmission
Ethernet FRAME must at least 64 bytes (512 bits). Padding is necessary if less. |
|
|
Term
| Virtual Local Area Network (VLAN) |
|
Definition
Can have multiple VLAN on a single LAN by adding new VLAN tag to ethernet frame (VLAN ID parameter)
VID has to be equal between the hosts for frame to be accepted.
One way to implement: Using a switch to associate a port with a VLAN so no VLAN tag is required. VLAN only exists on the switch.
Other way is if hosts are VLAN-aware and VLAN tag is added to ethernet frame.
In order for two VLANs to communicate, they need to communicate through a router. |
|
|
Term
|
Definition
If VLAN tag is in ethernet frame, the type is set to 0x8100 to indicate VLAN tag
VLAN Tag format: VLAN Tag Type, VLAN Tag Control, Ethertype.
Tag control has 3 parts:
1. Priority value - Used to specify frames priority
2. Drop Eligibility Indicator (DEI) - indicates frames eligble to be dropped in presence of congestion
3. VLAN Id - Identifies VLAN frame belongs to |
|
|
Term
|
Definition
| Increase privacy in network by segregating traffic in a LAN. Reduces BUM traffic as it only participates on same VLAN as sender. |
|
|
Term
|
Definition
| A switch has a separate FDB for each VLAN. One switch can act like multiple virtual switches (one for each VLAN). Each VLAN acts as its own Broadcast domain. |
|
|
Term
| VLAN with multiple switches |
|
Definition
| When switches associate each physical port with a specific VLAN. A physical link is needed between switches for each VLAN. |
|
|
Term
| Why can VLANs over multiple switches cause scalability issues and how can it be resolved? |
|
Definition
Since each port needs to be associated with a specific VLAN, each inter-switch port can only carry frames belonging to that VLAN.
Instead, allow each ethernet port to carry frames from multiple VLANs via VLAN trunking (single high-bandwidth port to carry VLAN traffic between switches). |
|
|
Term
|
Definition
Only 4094 VIDs possible. Use two VLAN tags, an outer VLAN and inner VLAN tag. This is QinQ encapsulation.
Each customer can have 4094 VLAN tags in its network, up to 4094 customers. |
|
|
Term
| Link Redundancy on full-duplex |
|
Definition
| Logical bundling of multiple links between two devices via a Link Aggregation Group (LAG) to provide redundancy |
|
|
Term
|
Definition
Topology with multiple paths to reach same destination with only one active path between two switches at a time. If a switch on the active path fails there is at least one other path that can carry traffic.
Use Spanning Tree Protocol (STP) to avoid forwarding loops. |
|
|
Term
| Advantages and disadvantages of redundant topology |
|
Definition
Advantage: protection when entire switch fails
Disadvantage: broadcast store or FDB instability |
|
|
Term
| Link Aggregation Group (LAG) |
|
Definition
Aggregate multiple physical links between ethernet devices so they are equivalent to a single logical link. Ports on a LAG can be of same speed or different speed.
Leads to increased performance and resiliency
Two things must be true:
1. All links must be full duplex and have same speed
2. Implementation must not reorder frames as they are transmitted across the group
3. All ports need to have same characteristics
4. Port must have limited or disabled autonegotiation
A LAG is a good solution for providing link redundancy between neighboring ethernet devices. It cannot provide end-to-end path redundancy however. |
|
|
Term
| Link Aggregation Control Protocol (LACP) |
|
Definition
| Standardized method for implementing LAG among different manufactures dynamically. |
|
|
Term
|
Definition
| Determines behavior of a LAG when number of available links is less than or equal to a threshold value |
|
|
Term
| LAG Port Threshold Action |
|
Definition
Down - if the number of available links is less than or equal to threshold, LAG is operationally down
Dynamic-Cost - if number of links is less than or equal to the threshold, dynamic cost is used to determine LAG cost
Static-Cost - If number of links is less than or equal to the threshold, specified cost is used to determine LAG cost |
|
|
Term
|
Definition
| If number of links is greater than port threshold and dynamic cost is enabled, path cost is dynamically calculated whenever there is a change in the number of active links. |
|
|
Term
|
Definition
Used by routing protocols for route selection.
If LAG 1 between nodes 1 and 2 has 3 links, and LAG 2 between nodes 1 and 3 has 5 links, and each link costs 100, then the cost of the logical link in LAG 1 is 33 (100/3) and in LAG 2 is 20 (100/5).
Number of links is determined by the number of ports configured on the LAG. |
|
|
Term
|
Definition
Is we assume LAG 1 has a link cost of 33 (100/3) and LAG 2 has a link cost of 20 (100/5)
If a phsyical link in LAG 1 fails and dynamic cost is enabled, then the new cost becomes 50 (100/2) as there are only 2 links.
If the LAG has a port-threshold of 1 and action down, then if 2 of the 3 links fail (only 1 link left), the LAG is down because it is less than or equal to the threshold value and the action is down.
In LAG 2, dynamic cost is not enabled. If a link fails, the cost does not change if a port is down. However, if port-threshold is configured to a value of 3 with an action of dynamic-cost, then if a 2nd link goes down, port-threshold value is met and the action is taken. New cost is now 33 (100/3). |
|
|
Term
|
Definition
Switch 1 sends copy of packet to all switches on the topology. Last switch receives all copies of data. It sends back each copy to the switches except the one it received from that switch. Cycle goes back and forth, multiplying along the way.
L2 has no method to discard looping frame, unlike L3 which uses TTL (time to live). Instead STP is used to label the frames and discard them based on their label. |
|
|
Term
|
Definition
| Switch 1 sends frame to all switches. It receives multiple copies from destination. It will learn the port to send the frame to but then keep switching between ports as it receives copies back. Modifying FDB at high rate causes instability. |
|
|
Term
| Spanning Tree Protocol (STP) |
|
Definition
Prevents loops and allows for path redundancy in ethernet network by blocking as many ports as needed within the switch that has it enabled. Ensures single path between pairs of switches.
If a switch fails then STP will update the calculation to use a standby path.
An active path chosen by STP may not be the shortest or least-cost path. |
|
|
Term
| What are the functions of the Link Layer? |
|
Definition
| It is the interface between the physical layer (L1 MAC address) and the network layer (L3 Router). It prevents IP from knowing how packets get from host to router. |
|
|
Term
| What are the characteristics of ethernet? |
|
Definition
| It is a collision-free transmission of packets on a point-to-point interface using MAC addresses to identify devices. |
|
|
Term
| What is CSMA/CD and why does it result in duplex operations? |
|
Definition
CSMA is Carrier Sense Multiple Access with. Hosts will sense the network to determine if the medium is free to send. CD is collision detection which prevents collision between hosts.
This is half duplex because collision detection prevents transmission of packets by multiple hosts. If two hosts packets collide, the network becomes jammed and no hosts can send traffic. In CSMA/CD only one host can transmit at a time. |
|
|
Term
| What are the differences between an ethernet switch and a hub? |
|
Definition
A switch provides full-duplex capabilities on point-to-point interfaces. It can make intelligent decisions about how to send a frame (FDB).
A hub is only able to do half duplex transmissions. When it receives a packet it automatically forwards it to destination ports. |
|
|
Term
| When does an Ethernet switch record a MAC address in its MAC FDB? |
|
Definition
| When a switch receives a packet from a device, it records the source MAC address and interface that packet arrived on into its FDB |
|
|
Term
| Differentiate between a collision domain and a broadcast domain? |
|
Definition
A collision domain is when two or more endpoints are connected either directly or via a hub. If a hub is in between CSMA/CD is mandatory. If no hub, collision will only occur if redundant cabling is not installed.
A broadcast domain is when every device will receive and process all broadcast packets. |
|
|
