JNCDS-WAN flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Requirement traceability matrix
- A table that maps each business or technical requirement to a design element, owner, and validation test so that no requirement is left unaddressed.
- Peak aggregate bandwidth
- Estimated by multiplying user count by per-user bandwidth, then by a concurrency factor; add 20-30 percent headroom for growth and burst.
- Availability formula
- Availability equals MTBF divided by the sum of MTBF and MTTR; 99.99 percent availability permits about 52.6 minutes of downtime per year.
- Design horizon
- The planning period, commonly three to five years, over which projected user and traffic growth is applied using compounding to size ports and bandwidth.
- Concurrency factor
- The fraction of provisioned users active at peak; it is used in capacity formulas to avoid sizing for every user simultaneously.
- Mandatory versus desired
- A requirements classification that separates non-negotiable must-have constraints from optional preferences, guiding trade-offs when cost, schedule, or technology conflict.
- Security zone
- A logical SRX grouping of interfaces that share a security policy; traffic between zones is controlled by first-match policies, with a default deny.
- IKEv2 Phase 1
- Negotiates the IPsec security association encryption, integrity, and Diffie-Hellman group to build a secure management tunnel between peers.
- IPsec Phase 2
- Defines the child security association parameters, including encryption and integrity algorithms, traffic selectors, and lifetime, protecting actual data flows.
- Control plane policing
- A firewall filter or CoPP policy applied to a loopback or Routing Engine interface that rate-limits and filters traffic destined to the device.
- 802.1X port authentication
- An IEEE access-control method where a supplicant authenticates through a switch port to a RADIUS server before network access is granted.
- Series availability
- For components that must all work, overall availability is the product of individual availabilities; adding a series element always lowers end-to-end availability.
- Parallel availability
- For redundant components where one suffices, availability equals one minus the product of each component unavailability.
- BFD
- Bidirectional Forwarding Detection is a lightweight hello protocol that detects path failures in milliseconds and triggers routing or redundancy failover.
- Commit confirmed
- A Junos feature that applies a configuration change temporarily and automatically rolls it back unless the administrator confirms it within a set period.
- Streaming telemetry
- A push-based monitoring method that continuously sends structured operational data from network devices to collectors, enabling finer granularity than periodic SNMP polling.
- Collapsed core
- A campus design where distribution and core functions share the same switches, reducing cost and hops in small or midsize sites.
- PoE budget
- The total power a switch can deliver to powered devices; sum each device class maximum and reserve about 20 percent headroom.
- Virtual Chassis
- A Juniper feature that combines multiple EX or QFX switches into one logical device with a single management IP and control plane.
- MC-LAG
- Multichassis Link Aggregation groups links from two switches into one logical bundle, providing active-active multihoming and device redundancy.
- Uplink oversubscription
- The ratio of total access-port bandwidth to uplink bandwidth; lower ratios reduce congestion but require more uplink capacity and cost.
- BPDU guard
- A spanning-tree protection feature that error-disables an edge port if it receives a bridge protocol data unit, preventing accidental loops.
- Hybrid WAN
- A WAN that combines private circuits such as MPLS with internet broadband or cellular links, using policy to steer traffic by application or SLA.
- IPsec overlay
- Encrypted tunnels built over untrusted transports such as the internet, connecting branch and data-center sites into a virtual private network.
- MSS clamping
- Adjusts TCP maximum segment size on tunnel interfaces to account for IPsec or other encapsulation overhead, preventing fragmentation and PMTU black holes.
- Local preference
- A BGP attribute used inside an autonomous system to prefer one exit path over another; higher values are preferred in best-path selection.
- Dual CPE redundancy
- Two customer-premises routers at a site, often with separate circuits and first-hop redundancy, remove a single device or link failure.
- Spine-leaf topology
- A data-center architecture where every leaf switch connects to every spine, creating predictable East-West paths and equal-cost multipathing.
- EVPN-VXLAN
- A network virtualization design using MP-BGP EVPN for MAC and IP reachability and VXLAN encapsulation for Layer 2 over Layer 3.
- Oversubscription ratio
- For data center, the ratio of downstream-facing port bandwidth to uplink bandwidth; 1:1 is non-blocking, while 3:1 allows moderate oversubscription.
- ESI-LAG
- Ethernet Segment Identifier Link Aggregation Group enables EVPN multihoming so a host can connect to multiple leaf switches with active-active links.
- RoCEv2 lossless
- RDMA over Converged Ethernet version 2 uses priority flow control and ECN to avoid drops, supporting low-latency storage and compute traffic.